Right rear locking up long before other brakes applied..

[Christian Nelson]

Really scratching my head on this one.

Just got another truck, an 84 1/2 ton.

I barely touch the brake pedal, and the right rear locks up HARD..

Bled the brakes, checked for adjustment, spun the adjusters, etc nothing frozen. From what I can tell, no air in the system, the lines don't look pinched, etc. I get a nice squirt of fluid from both rears. I get fluid from the fronts too, and the other brakes do apply when I depress the pedal further, but when I barely touch the pedal the right rear locks right away. I even adjusted the shoes way down, and after about 2 presses, it was right back to locking up..

I even checked to see if someone put both front shoes on one side, and both rears on the other side. All looks good.

I haven't replaced all the parts yet. I figure if I am going to do that, I will just switch to rear disks.

Anyone have any ideas of what to check?

 

[89Suburban]

My first thought was contaminated liner material.

 

[350runner]

Shoes on backwards?

Sent from the dust in front of you!

 

[Christian Nelson]

My first thought was contaminated liner material.

Don't see any, both sets of shoes look the same, no sign of leaking axle seals, or cylinder..

Shoes on backwards?

Sent from the dust in front of you!

Short is in front, long is in back on both sides..

I tell ya, this ones got me puzzled!! Can't be proportioning valve, because it's only one sid eon back. It's just a "T" fitting back there!!

Part of me is wondering if the line is plugged on one side, but I get a pretty good squirt of fluid from the bleeder on both sides. Both cylinders are moving, checked with drum on and off. Even switched the sides the drum was on!

Sprayed brake cleaner on everything to get a good look. Now, we have snow dumped on us. I am worried about that wheel locking up and putting me in a ditch though in the snow.

I figure I was wanting to do a disc conversion anyhow, so maybe come spring while I am doing my exhaust, I might redo the whole brake lines, etc..

But, if it's something simple, It sure would be a shame to not know what it is!!

 

[J Knight]

The only thing I can think of is the left wheel cylinder might be slightly corroded just enough to not give adequate pressure to the shoes and forcing the excess pressure to the right side. Just a guess.

 

[350runner]

Sounds like a good possibility. It is very mind boggling tho

Sent from the dust in front of you!

 

[89Suburban]

Yeah I am thinking wheel cylinder issue on one side or the other.

 

[350runner]

Well lucky it's a cheap part

Sent from the dust in front of you!

 

[chengny]

After you have adjusted the shoes way from the drums:

I even adjusted the shoes way down, and after about 2 presses, it was right back to locking up..

Take a ride (without braking in reverse). When you get a lock-up situation, pull the drum and check the shoe/drum face clearance.

If it is now tight, look at the shoe return springs as the issue:

You must be registered for see images attach

Also check that the linings are fully bonded/riveted to the shoes.

 

[highdesertrange]

what about the drum being out of round. highdesertranger

 

[Christian Nelson]

Thanks guys, some stuff to look at.

 

[Qwk]

Thread back from the dead!


Did you ever figure out this issue? Mine is doing the same exact thing! I have manual brakes and I about put it on the sidewalk when I was getting off the highway!

Craig

 

[Christian Nelson]

Haven't had a chance to check this out, I blew one of the front brake lines, and it needs a starter, and a battery now, so I'm now trying to figure out what size bulk brake lines to purchase, and what size ends..

Thinking I am going to go with Nickel copper lines, so they don't rust.

 

[Jarhead79]

My 92 locked up randomly after hitting bumps, replace the adjusters, mine were bad and after driving they expand out and when is hit a bump its lock up!

 

[Camatruder]

I had the exact same issue and after a lot of tryal and error i had the drums machined in a shop as a last resort and all was well again.