GMC Suburban Brake-Booster Boost

Back in the March 2004 issue, I noticed the “Brake-Booster Blues,” in which Robert Pascal was describing a hard brake-pedal problem on cold mornings (on a 1996 Chevrolet G-3500 van). The advice you gave him was very good. I had the same problem about 10 years ago, but with a different solution.

I own a 1988 GMC Suburban R-2500 with a 7.4-liter engine. While in the High Sierra, I had the daylights scared out of me when, on a cold morning as I pulled out of a campsite, I tried to stop at the highway entrance. I had full pedal pressure, but no braking at all. Luckily, I emerged from the incident unscathed.

After some research, I discovered a technical service bulletin on this exact problem. It was TSB 88-T-121 dated June 1988.

— E.P., South Pasadena, California

A. Thanks for sharing your experience, E.P. This TSB calls for the replacement of several components that connect the brake booster to its vacuum source with higher-flow parts. Although this TSB does not apply to the G-vans, it does cover many Suburbans (1987-88 R/V-20) and pickups (1984-86 C/K-20), and can potentially help quite a few readers who still have these models.

— K.F.


Ken Freund’s more than three decades of auto-repair experience and 20-plus years of RVing helped him author numerous books and articles on vehicle repair. In addition to RV Clinic and Performance, he writes the Powertrain column in MotorHome magazine. Ken has been a California Automotive VO-Tech and Smog-Test Program Instructor and an ASE-certified Master Automobile Technician.

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