To complement Trailer Life’s long-running RV Clinic column, we’ve launched an online technical question-and-answer section devoted to diesel tow vehicles.

Topics cover all aspects of diesel vehicles from engines to transmissions, gearing to fuel economy and tires to turbos. Each month Bruce W. Smith responds to one question in depth, and readers’ comments add to the conversation.

January 2020

2011-2016 Duramax Fuel Concerns

February 2020

Towing with Older Diesels

March 2020

Troubled Power Stroke

April 2020

Improving Airflow

May 2020

Faulty Block Heater

June 2020

Max Engine RPM

July 2020

Preventive Maintenance

January 2019

Diesel Deletes, Good or Bad?

February 2019

Axle-Ratio Selection and Fuel Economy

March 2019

Tow-Rating “Recertification”

April 2019

Lift Pumps

May 2019

Fuel Mileage and Engine Cooling

June 2019

Ford DPF Cleaning

July 2019

Replacing Head Studs and Fuel Filters

August 2019

Horsepower and Torque Limits

September 2019

Hard -Starting Cummins

October 2019

Oil Temperature and Change Intervals

November 2019

Turbo, Unison Ring and Position Sensor

December 2019

Oil Change Intervals and Analysis

Ask a Question

If you have a question about maintenance, repairs or upgrades to your diesel truck, SUV or van, scroll down to the Leave a Reply box at the bottom of this page. Please include your full name, city and state or province.

Bruce W. SmithA respected automotive and RV journalist and longtime Trailer Life contributor, Bruce W. Smith has held numerous editorial titles at automotive and boating magazines, and authored more than 1,000 articles, from tech to trailering. He considers his home state of Oregon a paradise for RVing and outdoor adventure.



  1. I have a 2013 Chevy 2500HD. I’ve heard of people removing the DEF system to get better performance. This seems like a complicated process. I’m assuming this would involve a new CPU chip. What if I needed to take the truck to the dealer for service? Would they still service it? I have 65,000 miles on it, but I would wait until the warranty ended before I did this. Thank you.

  2. I have a 2012 GMC 3500 Duramax. I am being told to have it “deleted” by most everyone. What is your opinion? Advantages and disadvantages?

  3. I have a 2015 Ram 1500 EcoDiesel. I’m curious about burning biodiesel. I’ve read some of the pros and cons, and I’ve read that, initially, this may require a fuel-filter change, as the biodiesel is a solvent and will dislodge some sludge. I’ve gone through that and determined I’m comfortable with the procedure. Generally, I’d like to hear your take on running biodiesel, and, specifically, I’d like to know how quickly that fuel filter will clog up and what that will look like (will I get warnings from the computer, or will it just fail?), and if that will be a frequent issue going forward. What if I’m switching back and forth, as biodiesel is not readily available in many regions?

    • Thanks, Bob. Bruce W. Smith has added your question to his list to consider for future Diesel Tech Q&A posts. In the meantime, he offered this brief reply:

      Prior to 2007, all diesels were B100 (100 percent biodiesel) compatible. After that, the EPA changed the emissions standards on diesels, so they now require at least B15 (15 percent biodiesel) fuel. Today’s diesel engines can run on B20 — but only if that biodiesel meets ASTM D7467-17 standards — which “home-grown” biodiesel probably doesn’t.

      As for fuel-filter plugging, early on that was a problem — more so with those making their own biodiesel than biodiesel sold by large manufacturers. Here’s a good explanation:'s/06-1.pdf

  4. Two questions:

    1) I’m debating between 3.42 and 3.73 axles on the new Ram 3500 diesel dually. I understand fuel mileage will be better with the 3.42, but how much better under similar conditions — e.g., pulling a large fifth-wheel? There are lots of factors besides axle ratios that won’t change (wind and tire-rolling resistance, for instance), so I’m guessing the difference will be less than the 3.73/3.42 ratio would indicate.

    2) With HD pickup manufacturers locked into the horsepower/torque race, I’m guessing they’re primarily retuning the same engines and pushing ever closer to the limits of what the parts will handle. At what point will the drive for more horsepower/torque affect engine longevity? To what extent can reduced longevity be mitigated by taking it easy and not burying the go pedal in the floor?

    • In reply to Michael Brown: Upon investigating a computer-chip enhancement that would potentially improve torque and horsepower on my 2016 Ford F-250 6.7-liter turbo diesel, I was informed by Bullet Proof Deisel in Arizona that my truck was just fine, and anytime one starts noodling around with these kinds of enhancements the potential for engine problems down the road increases. Is this true?

      • Bruce W. Smith replies: That is true, Tony, and expert diesel-performance shops such as Bullet Proof Diesel make a good part of their income doing repairs to customers’ diesels that have had their engine’s “noodled with” at one time or another. Power-enhancement modifications such as programmers, tunes and deleting or modifying the EGR system do improve overall torque and possibly fuel economy. The downside, other than the potential to run afoul of state and federal emissions laws, is making more power puts greater stress on all the engine’s internals as well as the drivetrain components from the transmission to the axles. Making more power in a diesel means the engine is generating more heat in the turbo and cylinders, so the ability of the cooling system, intercooler, fuel and engine-oil cooler(s) are also being stressed more than what they were designed to handle.
        Is adding a programmer (“chips” haven’t been used in for decades) a bad idea? No. If it’s CARB-approved and 50-state legal, all should be fine, as long as it’s used as the aftermarket manufacturer recommends. But again, an engine that’s been modified to make more power isn’t going to have the life expectancy of one that’s stock — all other things being equal.

  5. I’ve been thinking of going to a K&N filter or filter-charger system on my 2018 Ram 2500. I’ve been told not to do this. I’ve used the aftermarket air-filtration systems on my gas vehicles before and was happy. Pros and cons on doing this with my diesel?

  6. I am new to the diesel world. That being said, we are considering buying a 2010 Ford F-350 dually with a 6.4-liter diesel. I have read that this motor is not that good. What are the thoughts?

  7. As a newbie with a diesel pickup (2017 GMC HD 2500 with Duramax), I would like to know the maximum rpm that the engine can be used with the engine brake down a hill, and if I have to go up or down the gears (manually) on L position to avoid this having an rpm too high.

  8. I have a 2001 Chevy 2500HD with Duramax and currently have 105,000 miles. I have done oil changes and lubrication, plus three transmission services during that mileage period. I have not had to replace any engine parts, other than a water pump and serpentine belts in the 16 years I’ve owned this rig (purchased used from a rental agency in 2003 with 12,000 miles). What engine-related issues should I have addressed to continue this pattern of use; i.e., less than 10,000 miles per year?

    • Bruce W. Smith replies: The LB7 Duramax (2001-2004) is a good engine, and treated as you do, it’ll prove reliable for a long time. But like all diesels, the LB7s have their own little array of mechanical issues and concerns that have cropped up over the years. Unfortunately, one to prepare for sooner than later is replacing the injectors. The original OEM injectors are prone to cracking between 80,000 and 125,000 miles, which is right around the mileage your truck has reached. This results in a smoke haze at idle, an increasing loss in fuel economy and diesel getting into the engine oil, increasing the volume in the oil pan. The only fix is having all the injectors replaced with aftermarket ones, along with new glow plugs and high-pressure injection lines that feed the injectors.

      The latter are prone to corrosion and restricted flow, which also leads to poor fuel economy, loss of power and, of course, fuel leaks at the injectors. Always replace the injector lines when replacing the LB7 injectors. You can find complete kits to do this for less than $2,000. It’s a labor-intensive job, so if you aren’t doing this yourself, be prepared for the added costs. The glow plugs can be a problem removing because they tend to seize in the aluminum heads. Along those same lines, so to speak, the LB7 fuel lines from the tank are known to rust out, air leaks develop because of loose fuel-line fittings, and O-rings leak at the fuel-filter housing.

      While the injectors and glow plugs are being replaced, it’s a good idea to have the heads pulled and the head gaskets replaced. A lot of these engines experience head-gasket failure in the 100,000- to 150,000-mile range. This can be easily checked by squeezing the top radiator hose after the engine has been warmed up and then shut off. If the radiator hose is hard, the head gaskets are problematic. Leaking water pumps, as you already know, were also a common replacement item on the LB7s.

  9. What is the main cause of a 2003 Dodge Ram Cummins with 150,000 miles that starts really well in warm weather or with the heater plugged in but is very hard to start in cool or cold weather? The engine cranks well, and no codes show up when checked, with the ignition switch on and off using the “three-times” method.

  10. What is the cause and correct remedy for a squeaking exhaust brake on my 2008 Ram 3500 with just over 100,000 kilometers [62,000 miles]?

  11. I have a 2006 Siveraldo Duramax pickup. The stock fuel filter has a water-detection device that has never produced a warning in the 155,000-plus miles on the vehicle. I have been told the Cat 1R-0750 filter is a better filter, but it does not have a connection for the water detection. Should I be concerned about this? Does the Cat filter trap any water in the bottom of the filter, even though there is no way of sending a warning to the instrument panel?

    • Bruce W. Smith replies: The reason you’ve never seen a warning is because there’s never been enough water in the fuel to trip the sensor. Be thankful for that. It’s my opinion that it’s best to use only the GM fuel/water filter or a direct replacement such as the Racor Coalescer Fuel Filter (PFF50216) on any of the 2001-2016 Duramaxes. It takes only one hit of water-contaminated diesel to result in a very costly Duramax repair job. (The high-pressure injection pump and injectors really don’t like water.) That Water-in-Fuel (WIF) sensor in those filters at least gives the driver a heads-up that there’s an issue, and the engine needs to be shut down immediately.

      The step design of both the GM and Racor fuel/water-separator filter provides a little additional space for water to get trapped before it can head toward the high-pressure injection pump and on to the injectors. When you do replace the filter, don’t overtighten the WIF when you put it back on the new filter. GM techs say to tighten it finger-tight plus a quarter turn. Overtightening the sensor will surely crack it. This will cause air to get into the fuel system as the injection pump is pulling the fuel from the tank, and when that happens the engine will either not start or start then die. I also suggest stretching the largest O-ring a couple times before putting it on the new filter. This seems to make the O-ring fit perfectly when the new filter is installed.

  12. I have a 2015 Ford F-350 6.7-liter, and the diesel exhaust fluid (DEF) light/system check just says “OK.” It doesn’t indicate half-full or anything. I drove a later model, and it actually shows DEF level when doing a system check. Does the 2015 have a level indicator for the DEF that I can’t find?

  13. I have a 2013 HD Chevy diesel with 135,000 miles, and the check engine light (CEL) just came on and says “Service Exhaust Fluid System.” I have checked and topped off the DEF fluid, and still the message remains on. What is your best guess for what is causing the problem?

  14. I have a 2006 Chevy HD 6.6-liter Duramax and am considering using the Sinister Diesel CAT fuel-filter conversion kit. But I’m concerned about doing without the OEM water-in-fuel warning and extraction system. YouTube videos laud conversion primarily because of particulate size and less expensive filter but fail to address the water issue. Any guidance would be much appreciated.

    • Bruce W. Smith replies: The water-in-fuel (WIF) sensor on the GM filter is there for a reason — to warn the driver there is water in the fuel. If water gets past the fuel filter, then the injection pump and injectors take a huge and costly hit. RVers are the most likely to get a bad batch of diesel as they travel around the country, sometimes not having a choice as to where they refuel. The secondary CAT filter does a great job filtering small particulates and is less expensive than the OEM filter. But you can buy a lot of those OEM fuel filters for the price it’d cost to replace an injection pump and/or set of injectors, should you get a water-laden batch of diesel along the way.

  15. I have a 2013 Ram 6.7-liter diesel with 54,00 miles on it. The owner’s manual says to replace the two fuel filters every 15,000 miles. That costs $300 at the dealership. Is there any way to extend the interval and stay within the warranty?

  16. My questions concerns my 2005 Dodge Ram tow vehicle. I have the 5.7-liter Cummins diesel engine, and it is beginning to show some disturbing symptoms. I’m having a general power loss, and when I brought it into the mechanic, he replaced the fuel fiter/lift pump with a FASS system. While this helped a bit, I feel that my power loss issue remains. To me it sounds like the turbo is not providing the usual boost based on the lack of the turbo “whine” and the usual g-forces when the turbo kicks in. I’m also seeing an unusual amount of black smoke upon start-up and when accelerating. I have cleaned up the MAF sensor, but that did very little to improve my performance woes. I would very much appreciate if you could help me diagnose and repair my power plant.

    • Bruce W. Smith replies: Black smoke usually means the engine is getting plenty of fuel but not enough air for the fuel being delivered to make a complete burn. Add the “general loss of power,” and the finger points to either an air leak between the turbo, intercooler and intake or a clogged air filter. It’s not unusual for the spring-tension bands on the connection boots between intercooler and intake to work loose, or the boots get a hole in them or split, resulting in a massive air leak.

      An air leak anywhere in the turbo/intercooler/intake loop will result in little or no boost, and black smoke as the result of not enough air flowing into the cylinders for complete combustion. It’s also common on those engines to have the turbo wastegate get stuck because the actuator can’t function properly from excessive carbon and soot buildup. If the actuator has the wastegate stuck in the open position, the turbo can’t build boost (power). The actuator can be replaced, but we’d suggest going to a remanufactured turbo. BD Diesel Performance and Industrial Injection, among others, offer several drop-in turbo options along that line.

  17. Can you explain why the 2018 Ram 2500 diesel (6.7L) 4WD has a higher tow rating with the 3.42 gears at 17,160 pounds than it does with the 3.73 gears? When you request the fifth-wheel towing package option, it always defaults to the 3.42 gears only. From what I’ve seen on the 2019 Ram 2500 available information, the tow rating is up to around 19,000 pounds, but it still shows the 3.42 gears and not the 3.73.

    • For this question, we contacted Nick Cappa, communications manager at FCA’s Ram Trucks division. Here’s his reply: “You cannot order a Ram 2500 with diesel and 3.73 gears. Sounds like Buck France is seeing a 6.4 V-8 with 3.73 gears, which would have a lower tow rating.

  18. I own a 2006 Chevy 2500HD 2WD extended cab with 130,000 miles on it. I can’t seem to get more than 11.5 to 12 mpg, whether I am towing or not, on hills or flat land. Any suggestions? My other concern is that I can’t keep the truck cool when towing long grades like Oregon’s Siskiyou Pass. I have replaced the radiator and change the transmission fluid every 25,000 miles. I have had the gauges checked for accuracy. The truck is stock. I pull a 33-foot Dutchmen Grand Junction fifth-wheel trailer.

  19. I have a 2005 Dodge Ram dually Cummins that has begun having starting problems when the weather gets below 45 degrees Fahrenheit. It started tripping the Check Engine light, even when the block heater was plugged in overnight. The codes were MAP sensor, IAT sensor and battery-temp sensor. The air-intake heater works fine, and replacement of all sensors was performed. The block heater makes it easier to start, but why is the minimally cold weather here in southern Arizona affecting it starting?

  20. I am driving a Ram 2500 with a 3.42 axle ratio. I just bought a fifth-wheel that had a pin weight higher than the truck’s load limit. The dealer told me I could replace the coil springs with heavier duty coils and have it recertified, which I did. Did I do the right thing?

  21. I own a 2006 Chevy 2500HD Extended Cab with two-wheel drive. I have replaced the transmission tubes twice, and when I took it in for service recently, the dealership told me the hoses/tubes were leaking again. Are there any aftermarket braised-wire hoses that I can replace the OEM parts with?

  22. I have a 2016 Ram 3500 Crew Cab dually with the 6.7-liter Cummins. It has just over 45,000 miles, most of it towing our 2017 Keystone Cougar 367FLS fiver. Several of my friends who are also full-time RVers say that installing an aftermarket “lift pump” on the Cummins is a good investment. What’s your opinion?

  23. I drive a 1999 Ford with the 7.3-liter diesel engine and an automatic transmission. I pull a 2018 Keystone Hideout 21FQWE, which weighs 4,650 pounds (dry). There’s no problem with climbing hills or the weight of the trailer. My question is more about aerodynamics and miles per gallon. The Power Stroke feels like it’s pulling harder than it should when the truck is up to anything resembling highway speed, and depending on my right foot and the wind, mpg will be anywhere from 8 to 13.

  24. I have a 2106 Ford F-250 6.7-liter diesel that we tow a Heartland Big Country fifth-wheel with. On three occasions, only when towing, we suddenly start to lose power and get a warning light saying Drive to Clean. We have to unhook from the trailer and usually drive at highway speeds for 20 to 30 minutes to clear the warnings on the instrument panel. We can then hook back up to the trailer, and everything is fine. The pickup has 76,000 miles, with probably 15,000 of those towing. Any help would be appreciated.

  25. My 2001 Ram 2500 diesel 4×4 Ram Cummins 5.9-liter is a great truck. It has 200,000 miles on it and now takes a long time to get up to speed compared to when it was new. I would like to know how to get more power and if there’s a proven diesel fuel “enhancer” to get more mileage to the gallon. I get 12 mpg or so carrying an 8-foot, 1-ton slide-in camper. I don’t want high-priced additions that might screw up my wonderful truck.

    • Bruce W. Smith replies: There are a number of diesel fuel additives out there that clean and lubricate the injection system. I’d run through three- or four fill-ups treating each tank with Stanadyne Diesel Fuel Additive or Power Service Products Diesel Kleen. If you don’t see a marked difference in both power and fuel economy, it might be time to contact companies such as Sinister Diesel, Banks Power, Industrial Injection or Diesel Power Products to see what they’d recommend in the way of remanufactured injectors and a new, upgraded turbo.

      You don’t mention any injector or turbo changes on your Cummins. Turbos and injectors wear out, losing their efficiency and putting the hurt on power and fuel economy. On those second-gen Cummins, a lot of owners have replaced the stock Holset HX35/HY35 turbo with the Industrial Injection K27 Borg Warner Performance drop-in turbo so they can retain the factory exhaust brake. As for injectors, we’ve heard good results using Bosch RV275s, which are 40-horsepower over stock. They’d work well with the BW turbo. That combination keeps everything still close to “factory” and should be good for another couple hundred K.

  26. I have a 2008 Ford F-250 Super Duty diesel that has been lifted. I am experiencing a vibration at 1,500 rpm when accelerating, especially in fourth gear (auto trans) but also fifth gear. It is not a rough vibration but noticable. I have been told that if the drive line is at an angle due to the lift, it can cause that. I have not noticed that much of an angle in the driveline. Any feedback would be appreciated.

    • Bruce W. Smith replies: Typically, the pinion and transfer case output shaft angle on a lifted F-250 that has a two-piece driveshaft should be close to parallel (+/- 1 degree). Many lifts are 6-inch, which requires spacing the carrier bearing down between 2 and 3 inches. Typical lift-kit instructions say to shim it one way or another to get it where your truck doesn’t have the vibration. But the best way to rid a two-piece driveshaft from such vibrations is have a shop such as Tom Woods Custom Drive Shafts build you a one-piece driveshaft with a CV joint. That’ll cure all the ills that are inherent with two-piece driveshafts. Tom’s website also has a ton of information about the proper driveshaft angles and how to properly measure them. The vibration could also be “axle wrap,” which is very common with a lift that uses blocks in the rear, and the addition of taller, heavier tires. Axle wrap is the leaf springs bending slightly under initial load and then springing back, causing shudder or low-rpm vibration. Axle wrap happens in fractions of a second. Traction bars cure that issue.

  27. When I hooked up my trailer, a 2015 Shasta Revere, to my 2019 Ram 4WD 1500 Crew Cab with the 5.7-liter Hemi eTorque, the bed of the truck sags a lot. The truck has a 6-foot, 4-inch bed. I had my Triumph Street Triple motorcycle (414 pounds) and my Load-All ramp in the bed. I have the 3.92 rear axle and towing package. Even without the motorcycle in it (just the ramp), there is considerable sag when I hook up the trailer. I have to really tighten up the weight-distribution bars, but still there is more sag than I would like. Would you recommend changing coils or some other method to eliminate the sag? I don’t want to increase the carrying capacity, just eliminate the sag.

    • Bruce W. Smith replies: You didn’t mention what model Revere you are trailering, but a 32-foot 27BH, for example, has a dry weight just a few pounds shy of 6,000 pounds and a hitch weight of 604 pounds. Add freshwater, food, clothing and miscellaneous gear, and the weight of the trailer could easily be closer to 7,500 pounds with the hitch weight more than 750 pounds. That’s well below that model Ram’s maximum tow rating of 11,120 pounds and 1,680 pounds max payload rating. But the coil suspension on those tend to squat, as you have noted, without the self-leveling air-suspension option.

      The easiest way to keep the rear from sagging under such a load is to invest in a set of air helper springs, overloads or progressive-rate urethane-type helper springs to supplement the stock springs. SuperSprings offers urethane helper springs, and numerous aftermarket manufacturers offer air-helper spring kits for the Ram 1500s including Air Lift and Firestone Ride-Rite. Which route you take all depends on what level of investment, ride comfort and suspension adjustability works best in your situation. I prefer using air to control ride height over other helper spring options in this instance.

  28. I have a 2005 Ford F-350 DRW 6.0-liter Power Stroke with 110,000 miles. It’s been pretty trouble-free while pulling a 15,000-pound fifth-wheel trailer about 8,000 miles per year. I’ve always heard that the OEM head bolts can be a problem and would be better replaced by ARP studs. My question: Can you replace the head bolts with ARP studs one bolt at a time, carefully torqueing them to spec in a recommended torque pattern?

  29. I am considering buying a 1997 F-250 with 130,000 miles, 7.3L turbo diesel. I noticed white smoke coming out the tailpipe, especially when the engine was cold. Is the white smoke a concern?

    • Bruce W. Smith replies: White exhaust smoke on the old 7.3L Power Strokes isn’t that big of an issue on cold starts. The white smoke is actually caused by unburned fuel, and it’s normal on start-ups. If there’s an excessive amount, then that could be a cause for concern, meaning the glow plugs aren’t working properly or some are burned out, injectors are going south, the engine has low compression or even coolant leaking into the cylinders. If the white smoke disappears once the engine has warmed up for several minutes, I wouldn’t be worried. If the white smoke continues even after the engine is warm, and/or the engine is hard to start, then I’d have a diesel shop check it out. With those few miles, I’d bet the glow plugs (and maybe the wiring harness under the valve covers) need to be replaced.

  30. There are reports that the CP4 fuel-injection pumps are subject to failure. I have 102,000 miles on my 2012 Ford Super Duty and plan on keeping it for another 5 years. Should I consider being proactive and replace my pump now?

    • Here’s Bruce W. Smith’s reply to a similar question from another reader: We would be interested in actual CP4.2 failure numbers, too. But OEM manufacturers of products, especially vehicles, don’t generally disclose failure rates or discuss related warranty-repair information unless prompted by some legal action. A couple of class-action lawsuits were filed in the latter part of 2018 that are related to CP4.2 failures and owners of the affected vehicles seeking monetary compensation.

      Failures of the CP4.2 pump are enough of a perceived issue that aftermarket companies such as S&S Diesel Motorsport have gone to the time and expense to offer modified CP3 replacement pumps or bypass kits when the pump can’t be replaced by a better or more reliable version. Having an aftermarket product go through the CARB-certified, 50-state EPA legal process is a costly endeavor in itself, so these companies wouldn’t be doing this just for grins; they have consumers prompting them for the new products.

      For more on this topic, read Bruce W. Smith’s May 2019 Trailer Life article, “Diesel Heart Transplant,” about swapping out the Duramax engine’s CP4.2 pump for its modified predecessor.

  31. I’m fairly new to diesels. Mine is a 2002 with 150k miles on it. I tow a 10K fifthwheel. What are your recommendations for maintenance, fuel economy and any aftermarket products?

  32. Ted, as with any diesel pickup, clean fuel, lubricants and filters are the keys to extending engine and transmission life. If that truck is used for towing, at the very minimum follow the “Severe Duty” maintenance as noted in the owner’s manual. Personally, I’d change the oil and filter every 3,500-4,500 miles, have the Aillison transmission fluid and filter changed every 25,000 miles, the cooling system flushed every 50,000-75,000 miles (or every three years), and change the fuel filter every third oil change (GM recommends 15K or as indicated in the instrument cluster display). Of course, changing/cleaning the air filter every 25,000 miles or sooner if needed. It should be checked at each oil change. To maximize fuel economy, drive with a very light right foot and keep speeds below 60mph. As for aftermarket parts, it all depends on what your goals are. One of the best add-ons is an Edge Products Insight CTS2 (, which allows you to monitor all the engine functions from exhaust gas temperatures (EGTs) to boost, transmission to oil and coolant temperatures. If you want vehicle monitoring with six levels of switch-on-the-fly horsepower bumps, the Banks EconoMind with iDash 1.8 Monitor is a good choice.

  33. I have a 2007 GMC Duramax diesel 2500HD. Lately, the Check Engine light comes on and off periodically. A visit to the local GMC dealer indicated a code P003A within their code reader. The diesel mechanic was satisfied that the turbo is working properly and felt that the problem regarding the Check Engine light is the sensor. He cannot say that replacing the sensor will correct the light situation. It may be necessary to replace the turbo at a cost of $2,500. The sensor is approximately $1,000. Should I go with the sensor, or, as the mechanic has indicated, drive the truck until it loses power or black smoke comes out the exhaust? I would like another opinion before making my decision.

  34. I have a 2016 F-250. What do you recommend to keep me from having engine problems with the Bosch CP4.2? I have been using a fuel-injector cleaner in the fuel for a year now.

    • Bruce W. Smith replies: A lack of lubricity, air in the fuel or contaminants (water, dirt, etc.) in the fuel are the killers of CP4.2 high-pressure fuel-injection pumps. Using a high-end aftermarket lift pump and changing/checking the fuel/water filters on a regular basis are preventions for two of the three factors. Dosing your fuel with an additive that increases the lubricity of the diesel, such as Stanadyne or Diesel Kleen, is the third preventive measure. If you use a diesel fuel lubricity additive, use it in accordance with the manufacturer’s directions. More, or a higher ratio, of an additive isn’t better.

      For more information about lift pumps, see the April 2019 Diesel Tech Q&A.

      For more information on CP4.2 fuel pumps, see “Diesel Heart Transplant.”

  35. I have a 2013 GMC Sierra 2500HD with the 6.6-liter Duramax. At the last oil change, at 72,000 miles, I opted for 15W-40 Mobil synthetic at the advice of the shop. Does synthetic oil last any longer than regular oil in diesels, like they say it does for gasoline engines, or should I follow the Change Oil Soon message? Is synthetic oil a waste on diesels?

  36. I really appreciate the Diesel Tech Q&A addition. I have a question about my 2012 Ford F-350 6.7-liter diesel. There is an oil-temperature gauge, but no one can tell me what the upper limits should be and for how long. I have come up to 230 degrees while towing up a mountain grade, but it quickly drops to the 200- to 210-degree range when the grade levels off. The coolant temp never seems to get above the normal range. I use Shell Rotella T6 full synthetic 5W-40. I use the gauge to let me know when the oil is warm enough to begin towing.

  37. I have a 2015 Ram 1500 EcoDiesel that just turned over 34,000 miles. It has started losing coolant, about an inch in the degas bottle during a 600-mile trip I took last week. The dealer did a pressure check but found nothing. No visible signs of a leak or coolant in the oil. Any suggestions where the coolant could be going?

    • Bruce W. Smith replies: The first thought is it could be an internal exhaust gas recirculation (EGR) cooler leak. If the feed to the EGR valve shows signs of moist, sludgy soot, it’s a leak inside the EGR cooler. But that is rare on a diesel with as little miles as yours. Higher mileage engines see this because of the constant expansion and contraction the EGR cooler cycles through in its normal function cooling hot exhaust gases.

      Also consider that the coolant line to the turbo center section may be leaking. The turbo water feed tube is located under the intake in the valley of the motor and comes from the driver’s-side head. It’s made up of two hard lines that are connected by a rubber heater hose. The feed line uses two banjo fittings (19mm and 22mm) that have been known to loosen and leak. If they were to leak, the coolant would burn off on the hot turbo and exhaust and not show signs of a leak.

      Related to that is the rubber hose that’s part of the line. It’s known to fail with age from the engine/turbo heat. There are also two hard coolant lines that run from behind the water pump and under the intake. Those lines have O-rings to seal them from leaking. When they leak, it is very difficult to notice. The slowly increasing coolant loss could also be a water pump on the way to failure.

      All of the above would require a dealer to check out — or someone with the tools and diesel tech skills. Remember, tracking down leaks, especially coolant-related, can be very difficult. Your dealer will probably use a fluorescent dye poured into the coolant tank to make the source of the leak easier to spot.

  38. I have a 2003 Ram 3500 with a 5.9L Cummins and a 47RE transmission, with 160,000 miles. Everything is stock. I pull a fifth-wheel of about 14,000 pounds. It pulls, but not really enough. My question is whether I should invest in add-ons that will give me more power or bite the bullet and trade up to newer. I do love my truck. It is in good shape, and best of all is paid for. I could probably afford $6,000 to $7,000 for add-ons versus a new car payment. Is a new truck in my cards, or should I, and can I, get more power out of this truck?

    • Bruce W. Smith replies: Doug, this is a continuation of my answer to Tony Gotelli related to enhancing the performance of a diesel through the use of aftermarket parts. Aftermarket diesel-performance parts, when properly installed and the components matched for that application, can double the torque and horsepower of the 5.9-liter Cummins. The downside is they shorten the engine’s overall life span. To do things right with your 2003 5.9L 24V and maintain the best reliability as a daily driver, you should have the engine rebuilt. Then upgrade to a 57/65/14 Scheid Diesel Lightning turbo or BD Diesel Howler VGT turbo kit, 125-hp injectors, 150-gph lift pump (Air Dog or FASS), ARP head studs, rebuilt injection pump and Edge tuner. That should put you in the 450-hp/1,100 lbs-ft range.
      It’ll also cost between $8,000 and $12,000, depending on who does the work. In comparison, a 2020 Ram 3500 6.7L Cummins is rated at 370hp/850 lbs-ft torque, and it’s covered by a 60-month/100,000-mile warranty for both powertrain and engine. The benefit of stepping into a 2019/2020 Ram is the ride, handling and overall comfort, along with the strength and performance of the new diesel platforms, which are far superior to anything built back in the early 2000s. If you tow long distances or spend more than a couple months a year RVing, I’d sell the ’03 and step into a new truck instead of dumping a lot of money into the old one.

  39. I have a 2006 F-250, 6-liter engine. Lately, when towing my 33-foot fifth-wheel trailer, the hose from the turbo has been blowing off when around 3,000 rpm on the turbo. What needs to be done, as it’s difficult to pull the rig uphill at just 3,000 rpm without blowing the hose off and having to replace and retighten same?

    • Bruce W. Smith replies: A common issue on 6.0-liters that’s most likely caused by the oily mist from the OEM crankcase vent (CCV) being routed back into the intake, causing oil to saturate the intercooler hose boots. (The mist also can create issues with the intercooler.) When the turbo builds boost, the oil-saturated boots blow off. Replace the OEM CCV with a Racor 4500, and install a vent kit available from Riffraff Diesel or Xtreme Diesel Performance. Ford issued a TSB back in 2015 addressing the issue: TSB 07-5-15, Intercooler Hose Blow-Off. You should also replace the OEM intercooler hose boots and clamps with upgraded aftermarket ones like Sinister Diesel, XDP, Riffraff and others offer.

  40. I have a 2017 GMC Sierra 2500HD with the L5P Duramax. We use it as a daily driver as well as pulling our camper. Is there an aftermarket gauge that would allow me to monitor the engine’s performance better than the stock gauges? What do you recommend?

    • Bruce W. Smith replies: Several aftermarket gauges will give you all the data you could ever need to know about what’s going on with your LP5. Two of my favorites are the Banks Power iDash 1.8 DataMonster and the Edge Products Insight CTS2. Either one of these monitors will give you instant digital readouts of everything happening under the hood in easy-to-read, multi-window displays that are totally customizable for whatever aspects of the engine’s operation you want to monitor. They also serve as data loggers and diagnostic tools. Anyone who tows trailers on a regular basis should have one of these to replace/supplement the OEM dash gauges.

  41. Is there one or more diesel manufacturers whose DEF component systems have proven to have longevity to match the engine? My 2013 MB 3500 Sprinter had the DEF components go south at 18,000 miles, outside of warranty on my dime.

    • Bruce W. Smith replies: Oh, don’t we wish! Unfortunately, at this time we don’t know of any Diesel Particulate Filters (DPF), EGR valves or other components that have direct contact with diesel exhaust that have the longevity of the engine they are on. Diesel exhaust is dirty. The exhaust carries a certain amount of particulates from the burned/unburned fuel, which is trapped in the DPF. When the DPF reaches a certain point, those particulates clog it up and create enough backpressure to trigger a “regen.” A regen cycle dumps raw diesel into the exhaust so that unburned particulates in the DPF are ignited and burned off. Regens help extend the life of the DPF. But at some point even regens can’t keep the DPF from plugging up, necessitating its replacement. Just consider the DPF, EGR valve and other exhaust-related components as wear items, much like belts and brakes, that will probably have to be replaced several times before the diesel engine they are on has run its course and needs a complete rebuild.

  42. I have a 2017 GMC 3500. There is a recall on the engine-heater cord with no current fix. What can I do since I moved to a state where it routinely gets below 30 degrees Fahrenheit?

  43. I have a 2016 Silverado with a Duramax engine and 24,000 miles on the truck. My question is in regard to the fuel filter. The truck is used only to pull my travel trailer, and it is stored in a heated garage during the winter. How often should I change the fuel filter? The driver information center (DIC) tells me the filter’s life is at 50 percent now. Simple math tells me the filter will not be due to be changed for another four years. Do I go with what the DIC tells me, or should the filter be changed more often?

  44. I have a 2016 Chevy 3500HD Duramax diesel. It has 60,000 miles on it, and I’ve been using Shell Rotella 15W-40 oil since I’ve had it. Can I change over to synthetic oil now without it hurting the engine? If so, what would you recommend?

  45. I enjoyed Trailer Life’s Chevrolet Silverado HD article about the new Duramax engine and its ability to handle far larger payloads. I have a Ram 3500 with the 6.7-liter diesel engine, and putting the truck near the weight limit seems to put undue wear and pressure on the braking. Do the new Duramax trucks have some secondary or auxiliary brake booster or heavier brakes?

  46. I have a 2005 GMC 2500HD diesel, and it has 150,000 miles on it. I have been using Amsoil 5W-40 Max-Duty synthetic diesel oil. My tech says I should have no issues running 10,000 miles between oil and filter changes. Do you agree?

  47. I have a 2015 6.6-liter Duramax and have heard about there being a problem with the injection pumps as the mileage nears the 100,000-mile mark. What do I need to know about this, if it is an issue?

  48. I have a 2015 Jeep Grand Cherokee 3.0L EcoDiesel with 103,000 miles on it. The oil temperature is getting way too hot in normal operation, not towing. I did an oil and filter change and also changed the thermostat. Antifreeze is normal levels; fans kick on when they are supposed to. I’m lost. I really don’t want to spend $800 on a water pump if that’s not the real cause. No leaks whatsoever on this vehicle.

  49. I have a 2016 Chevy 2500 Duramax with 65,000 miles. It recently started losing a very small amount of antifreeze, just enough to make the Add Coolant light come on. I’ve had to add fluid three or four times in the last 5,000 miles — maybe 1 to 1½ quart total. Any thoughts on this would be appreciated.

  50. My 6.7-liter is first-generation. Can you offer any advice on maintenance, driving habits and reported parts that I should look out for? I will say that it pulls 10,000 pounds with ease, and with the exception of that one issue, it’s been trouble-free.

  51. I have a 2013 f250 6.7 diesel and have noticed I don’t get the cleaning exhaust filter information any more also don’t use any def fluid.
    This has been going on for about 3000 miles

  52. If you are having a problem with a diesel overheating or going to limp mode when pulling uphill, clean your radiator with Purple Power or Krud Kutter from Walmart.

  53. On air intake systems for Diesels, have you considered a vacuum gauge? Installed between the filter and the turbo, it can tell you if the turbo is sucking hard, if you have a air restriction.

  54. Hello, I purchased a 2015, 2500 GMC Duramax, 4 doors with a 6.5 bed. I tow a 2017 32’ Jayco fitwheel that weights 9000 lbs dry. My question is simple, when I tow, am I better to tow on “Drive” and only use the towhaul option only when I travel though hills and mountain?

    I found that I am getting better gas millage when I don’t use the towhaul. Am I hurting the truck transmission by doing this?

    Thank you for your response.

  55. I have a 2014 Ram 2500 6.7-liter Laramie with the factory limited-slip. Truck just turned over 114,000 miles. After a few highway miles towing a 7,000-pound travel trailer, the rear differential starts chattering when making L/R turns from a stop once the differential fluid has warmed up. I recently changed the diff fluid (at 100,000 miles), refilling it with Mopar spec GL-5 gear oil. Should I have added anything to the gear oil when I changed it?

    • According to the maintenance schedule shown on page 132 in the “2014 Ram Diesel Supplement,” the axle fluid should be changed every 20,000 miles (32,000 km) when the truck is used for “fleet, off-road or frequent trailer towing.” With just one rear diff fluid change in 100,000 miles, what you may be experiencing are the early warning signs of a rear differential failure. Brian “Gus” Pyeatt at Yukon Gear & Axle says, “The factory [AAM TracRite GT] limited-slip in the fourth-gen Ram HDs are a helical-gear, or Torsen-style differential, not a clutch-style LSD. They use worm gears or screws to provide power transfer. They are normally very smooth and require minimal maintenance and no special additives with the GL-5 lubricant. As they wear, the screws and the bores that they ride in get larger and larger clearances. They eventually get to the point where rather than being held parallel, and riding against each other, they start to get cocked and dig into the case. This is the ‘chatter’ that is being felt once the gear oil has warmed up. What you are feeling is similar to the chatter of a drill bit being started crooked in a hole and the corners of the bit biting into the metal. The solution is replacement before the LSD completely fails. When one fails, it typically does so in spectacular fashion, taking the ring , pinion and bearings out with it.” As for an additive, such “friction modifiers” are used in clutch-type limited-slip differentials to reduce how aggressive they are in locking up. If such additives are used in a helical-style LSD such as in the Ram HDs, Pyeatt says, “that may actually compound the issue.” The Ram owner’s manual concurs, saying no additives are needed.

  56. Bruce, would like to chat with you, or text or email or whatever mode you might prefer… about your “project Deepwoods” Bronco of years ago? Really enjoyed that build, probably my favorite build ever! Thanks,

  57. On the issue of the Chevy Duramax 2016 loosing small amounts of antifreeze fluid. I had the same issue with my 2015 Duramax 2500. The technician could not find any obvious leaks so they ran a pressure test which failed the proper psi. They found a small leak in the radiator. I had the radiator replaced at our dealership. I was told that the radiators are now being made out of plastic components for the Chevy trucks. Can you tell me if that is true?

  58. Hi
    We live in Cincinnati Ohio. I have a 2000 7.3 diesel Ford F-250 super duty. We tow a 38’ travel trailer with it. It tows well. We are going out west next summer and I was wondering if I will have issues with the truck running well in the high altitudes? Is there some adjustments that need to be made prior to the trip? Will it tow ok in the high altitudes?

  59. I pull a 24 foot travel trailer with my 2016 GMC Canyon 2.8 diesel. When last I drove it I liked the package. It has had broken turbo connection problems (turbo itself fine) and plugged exhaust gas Filter problems. Between Covid-19 , the strike, and bad diagnostics I have lost now 15 weeks of use. Are these problems common, how can I communicate with G.M.? The dealer seems to try from time to time, but between us we have no idea when parts might arrive. Sitting in the lot it has suffered hail and tool theft problems.
    Dick Hodge

  60. Who makes the best or second best Diesel Engine and Transmission combination for a Super Class C motorhome with regards with towing capabilities

  61. I recently purchased a 2020 Sierra HD with the 6.6L duramax. I’ve noticed a knocking noise at idle from what sounds like is coming from the lower area of the engine. Dealer says it’s normal and not to worry about. I have heard it from other trucks. Can you tell me what the noise is and if it’s something to be concerned about?

  62. Bruce,

    I read your February 2020 article on replacing old injectors on the 7.3 L diesels. My 2003 has close to 300K and still runs good and was planning on replacing injectors and upgrading the turbo to a bank’s system. What are your thoughts on the turbo upgrade?

  63. Hi had a catastrophic failure of my EGR cooler in my 2017 ram eco diesel. The vehicle was under warranty and the cooler was part of a recall. Should I be worried about any long term damage? The tech said the intake looked fine but I’m concerned of long term problems. The engine also overheated upon failure of the cooler.
    Thank you
    Ontario, Canada

  64. I have a 2019 F-350 6.7 Super Duty with 12,000 miles on it.
    Pulling a small 5th wheel trailer with an OAL of 27 ft. and aprox. 8500 lbs. (loaded) over a 6 mile grade with the max. grade of 7%, the outside air temp. of 98 degs., the transmission temp. gets up to 226 degrees.
    Returning home over the same grade with the outside temp. of 85 degs. the trans. temp. was 216 degs. This is of course towing with trans. in “tow/trailer mode”.
    I towed w/an 08 Duramax before this Ford and pulling this same 5th wheel trailer ‘WITH’ a RZR on a trailer behind it, I never saw over 210 degrees.
    In talking to three Ford dealers locally about this, I’ve not been able to get any real definate answer whether the 226 temp. is a concern or not. I’ve not needed to pull the RZR behind yet with the Ford and I’m a bit worried now about doing so because of the 226 degs. w/out it.
    Once at the summit and going down the other side, it takes the full downhill distance of 6-8 miles before the temp. drop to below 210 an holds at roughly 210 -212 degs. on level ground. I might add that the tk. runs between 195 and 205 degs, (summer weather temps.) on normal, flat highway at highway speed w/only the tk. itself and empty.
    Should I be concerned about these temps. with a small trailer?
    Thanks for your thoughts.
    D. Walker

  65. I have a 2008 Duramax long bed crew cab. I live in the mountains outside of Denver at 7500 ft elevation. When I tow my boat (5000lbs) up I 70 from Denver, my engine starts to run hotter. About half way between normal and hot. This happens even when the temperature is in the 50’s. I can tow deeper into the mountains at any temperature or altitude and the engine runs at normal temps.
    Any idea why it runs hot towing at the lower altitude. My boat shouldn’t be too heavy for the Duramax

  66. I have a 2013 Duramax with under 85,000 miles. We travel with a 5th wheel camper. In 2016 while traveling out west, with 31,000 miles, the turbo went. In 2018, with 56,000 miles, the EGR valve went. In 2020, with 84,000 mile, the turbo and EGR valve went again. The dealer said soot buildup caused the issues. What am I doing wrong???

    Next, because of covid, and not using the truck much, The check engine light for exhaust fluid quality poor result. The dealer said to fill the tank with fresh fluid and drive. If that doesn’t fix it, it will go in for repair. This is just a reminder to those out there to keep fresh fluid and use your truck.

  67. I have a 2019 Ram 3500 with the HO 6.7 Cummins. Runs 10w-30 syn blend dealer/factory installed. I pull a fifth wheel toyhauler 16,800 gvw but never reach that. Is an oil temp of 239 too high pulling a 7 % grade for 10 20 minutes and then it cools right down on flats to low 200s? Should I go to a 0w-40 full synthetic?

  68. I have a 2020 Silverado 3 l diesel as of may of 2020 that has needed work at 15000 miles.
    excessive oil flow into pcv system required replacement camshaft housing.

    service people at the dealership don’t seem to say if this is a solid repair that will last –thought it was to have just a pcv valve replaced but not sure what was done if they list on the invoice for camshaft housing.

    where can I find out technical information so I can understand if I need to file for a lemon law case
    or clarify what this work means.

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