QuestionHi Harry, recently you answered a Q about rear brake shoe orientation on my Blazer. I'm hoping you can help with another issue.
I've owned this truck for some time and the brakes always felt mushy with long pedal travel. Pedal is solid with no boost (engine not running). I just refurbed rear and front brakes, including rotors, drums, calipers, wheel cylinders and flex lines... decent stuff, all Raybestos. Brakes were properly bedded. Rear adjusters were checked for function. System was flushed and new DOT4 fluid pressured in. Master cylinder was replaced within the last 8000 miles.
None of this has changed the pedal feel. I can stand on the pedal and not lock up... it stops but doesn't feel very modulatable (if thats a word!), particularly now that I'm towing a small work trailer.
The only parts that haven't been replaced are the booster, the proportioning valve, and the hard lines.
I'm stumped and beginning to think either booster is somehow bad, or it's just the way these trucks are.
Any insight?
Adding:
Guess you may want to know what we're talking about here. It's an '83 full size 4x4 Blazer.
AnswerThank you for the detailed information. Most inquiries I receive lack good information.
My 83 and 84 diesels have Hydroboost, so the boosters are different than on your vehicle (but I do not believe the problem is in your booster). I, too, have recently accomplished brake work on my trucks, though not replacing quite as many parts as you have.
I have no doubt that my brakes would lock up if I pressed the brake pedal hard enough.
My 1984 GMC shop manual states that brake pedal travel should be 3.5 inches, without power assist (by depressing the pedal three or four time to remove residual vacuum in the booster). Excessive pedal travel may be caused by: Air in the lines, leaking connections, leaking wheel cylinders or calipers, leaking master cylinder (internally or externally), loose or missing brake hardware, faulty metering (proportioning) valve, or incorrect wheel bearing adjustment.
To the above list I will add: The anti-dive valve located on the rear axle on some GM trucks. I have one on my K-2500 but not on my G-20. The valve controls rear brake line pressure depending on vehicle load. Also, an electric trailer brake controller could cause problems, though I have one on my K-2500 and it does not affect hydraulic braking action on the truck.
I would make certain that you were given the proper master cylinder for your vehicle. Parts people sometimes make mistakes. It might be the proportioning valve or a hard line that is leaking (rare, but it does happen).
I installed stainless steel braided brake hoses on my two Toyota MR2s (four wheel disc brakes) and noticed a big difference in brake pedal feel. I also put a set on my K-2500 but noticed less of a difference. They are not made for my G-20, but I had a bad hose cause a pull to one side, so OEM type hoses were installed. If I read your question correctly, you have already replaced the hoses.
If you want to try thet the stainless steel braided hoses, you can get them from Jegs, Summit Racing, and other places. Just be sure not to get a set for a lifted vehicle if yours is stock (or vice versa).
