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 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


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.


 

25 COMMENTS

  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: http://www.baldwinfilter.com/literature/english/10%20TSB'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?

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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?

  10. 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?

  11. 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.

  12. 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.

  13. First like to say,your column, one of the first thing I read in each issue, and save.
    As I,m fairly new to diesles. Mine is a 2002 with 150k on it. I tow a 10k 5 th wheel. What are your recommendations for maintenance, fuel economy
    And any aftermarket products.

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