Brake Question

[mopar1968]

Working on 96 Chevy 1500 4x4 Suburban rear brake's locking up,Trying to help out a friend, removed drum's everything looks good :!: :!:

[Harbone]

are they locking up hot or cold? after a short or long distance? do they release after it comes to a full stop? lots of scenarios here from bad proportion valves to sticky master cylinders. with drum's though it shouldnt take long to figure after a couple of different checks and tests...

[mopar1968]

They will lockup anytime, will do it in garage,driveway, hot or cold, only rear doing this, The guy i am helping don't have alot of money so i have got to be right on this one, they will release normal. Not sticking at all just locking up before front does. shoes looks good wheel cylinders good, no axle leaks. Just a quick lockup.

[MEMRACING62]

front part of master cylinder could be failing. porportioning valve failing,

[Harbone]

how is the condition of the brake fluid? colored, contaminated, milky, etc?

[mopar1968]

Removed all fluid and put new in, bleed out still same problem.

[Harbone]

its either the pro-valve or the master cylinder if the fronts are working OK. you would almost have to install some inline brake pressure gauge, try it in the back first to see if the brake pressure is "hanging" after the pedal release, if it is move up to the pro-valve (do GM's have a adjustable pro-valve on the back that senses how much weight is on the back like the old Ram pickups? I know those used to fail alot, thinking the truck was fully loaded down) check it again, if it still hangs move up to the outlet on the master cylinder. something is not releasing the pressure after the pedal release.

[mopar1968]

no it doesn't have the valve.

[itsabird]

i would take alook at the emerg brake cable, could be frayed and not released all the way, good luck.

[fla1976]

I would look for a flexible brake line that has been damaged and swells up. It will allow pressure to be trapped and drag the brakes.

[chrisr]

OK, are you saying that the brakes lock up while applying and let loose as soon as you let of the pedal or that they are staying locked after releasing. Alot of these answers are refering to the brakes staying on after you get off the brake but you kinda made it sound as if you meant the back lock before the front but release as soon as you are off the brake pedal. Just wanted to make sure which so you can get the right answers.

[RonOwensRacing]

Yep mark i think these guy's are on it i would check the proportioning valve it has to be getting a lot more pressure to the back to be grabbing the brakes harder and faster i have replaced the factory with a adjustable aftermarket one before to solve this kind of problem.

[mopar1968]

The brakes will release as soon as you let off pedal, Just when you apply brakes the rear will lock up, They are not sticking, and both sides will do it.

[mopar1968]

Found it rear brake shoes are contamintated with old rearend fluid from a old axle seal leak, installed new shoes problem went away

[Harbone]

well that was to obvious! guess the first question should have been "have you inspected the brakes?" :)

[dragonmaster093]

must be a mopar thing back brakes never work on those things them dodge guys foreget how to work on ones that do work lol sorry mark

[Harbone]

Nah, its a Dodge thing! I have a 97 Ram 4x4 that I have owned for 10 years and I have now officially replaced every steel brake line on the truck from the master cylinder down! they have all rotted away over time and I just did the 2 on the rear axle to the rear drums just 3 weeks ago...

[dragonmaster093]

lol aint that something my 77 monte has (to the best of my knowledge) all of the factory steel lines

[MEMRACING62]

lol aint that something my 77 monte has (to the best of my knowledge) all of the factory steel lines IN ILLINOIS BRAKE LINES LAST ABOUT 8-9 YRS. SALT EATS THE CRAP OUT OF THEM & EVERYTHING ELSE UNDER CARS & TRUCKS. ALL BRANDS THE SAME :(

[Harbone]

I have had some 25 year old cars in Illinois that havent rotted out like that! We get 8 year old Caravans that need metal line replacements. My grandpa has some middle 70's Mercury wagons that he has driven year round since day 1, everything has been replaced EXCEPT the brake lines. The good news is us Parts guys make a living from this! :lol:

[dragonmaster093]

iowa/sd/ne same way and thats where my monte has lived its life till i made the big move

[mopar1968]

Every car/truck i own has factory lines on them. So it isn't a Dodge thing it is a salt thing :!:

[MEMRACING62]

I dont notice a difference between any makes, salt eats them all.

[TheRabbit]

Every car/truck i own has factory lines on them. So it isn't a Dodge thing it is a salt thing :!:

WTH hell you putting salt on brake lines for?. Salt goes in your grits or on french fries. Sorry Mopar, couldn't resist.
Glad you got 'em going with very little cost.