Locking Rear Brakes

chevrolet
1500

#1

You guys are great! I have been a NPR listener for a long time now. Sometimes I will ask perfect strangers if they are familiar with NPR. People I know that like witty humor or they are just car nuts, I will tell them about your program and before you know it they are listening to NPR all of the time. The back brakes on my 1997 Chevy Z71 pick up are locking up and it blows the right rear (pasenger) wheel cylinder. I finally took it to a good local repair shop that I deal with regularly. They checked it out put another wheel cylinder on. I took it home. The next day I was pulling out of the garage, bingo, it locked up. I put it in 4 wheel drive to move it and it blew the right rear wheel cylinder again. They did not charge me. Again they checked it out and replaced the right rear WHEEL, said it was slightly warped. The brakes were OK for a while. Seemed like it wanted to grab after pulling away from the gas pump one day. (The brakes always grabbed and locked when moving “slowly” forwards or backwards.) A month went by until I was pulling out of a full service car wash. The brakes locked up, I put the transmission in low gear and it came loose, but with a bang. When it bolted loose, the bang sounded like it came from the left (driver’s) side rear wheel. The wheel cylinder did not blow this time. I do not think water is the problem. The car wash was the only incident when water was present. This has been going on for months. It is a very nice truck, but heck I am always concerned about being stranded or having no stopping power! I have an '89 Z71 GMC pick up with 372,000 miles on it and I am much more confident driving it, even though it looks like it has been in a national demolitiom derby. Can someone please point me in the right direction?


#2

I’m not by any means knowledgeable about GM brakes, but I’d search out and examine the brake line very carefully. If it is pinched, maybe from being hit by a rock, it could restrict the flow of fluid back, causing the wheel cylinder to build up pressure with each application of the brakes.

Does this have any relationship to you using the parking brake?

Sorry I don’t know more.


#3

My wifes Windstar had the same problem for a while and I found that the rear break shoes that were installed were the cause. I replaced them and the problem went away. The shoes were installed by a local mechanic who bought them at some store down the road famed for haven really bad parts.


#4

I’d also check the parking brake. These can malfunction and cause the rear brakes to lock. The brake doesn’t even have to be on for this to occur.


#5

Have an ASE certified BRAKE mechanic check your rear brakes for improperly installed parts, (like leading and trailing shoes reversed or installed upside down) incorrectly installed return springs, incorrectly installed emergency brake linkage and self adjusters. Also check the diameter of the rear drums. If they are worn beyond service limits, the self-adjusters will over-do it and lock up the brakes…


#6

Maybe a previous brake job included turning the drums past specification. As Caddyman said, check the inside diameter of the drums.