Mez

So i have an 86 gxl and despite the new rotors new front right calliper new pads and new master cyl the brakes still jam on. it’s really weird it’s not even when i use then they usually get stuck when i am just cruising along without using brakes at all. when they do jam the pedal gets really stiff like its pressed all the way down but it’s not like the system is building pressure. i am thinking it’s the brakes booster what do you guys think?

clokker

iTrader: (2)

Does sound like the booster.
First thing to check is the input rod from the pedal to the booster, make sure there is a bit of freeplay.

Mez

k how much freeplay?

Mez

ok i just did a test with turning the car off and playing with the pedal and it seems like it has excessive play with the car off i can depress the pedal 2 inches and turning the car on only give me another inch, inch and half

Mez

ok latest update. i had the brakes done by a mechanic less than a year ago because my parents didn't trust me to work on my own car annnd it was a poor choice. just pulled a tire off pretty much all the springs and stuff in the calipers are rusty and dont seem to be functioning and the pads drag on the discs constantly. woo professionals.

Mez

suggestions/how to fix this problem?

clokker

iTrader: (2)

While you had the caliper off did you retract the pistons?
They move freely?

Your original post still makes me think booster problems.

misterstyx69

iTrader: (142)

Check the Hose on the booster itself.There is a checkvalve IN it.
If the Valve is gone,then the booster gets air and can apply the brakes even when you are not pushing on the pedal.
This HOSE is located Between the booster and the Hard steel line on the Firewall.The hose is an ESS shaped Preformed Hose.FEEL it by squeezing to find the Checkvalve.(you can also take the hose OFF and Blow into it..it should By rights only allow air to Go From the booster to the engine.,NOT Both ways.)
I hope that may help if it is it.

clokker

iTrader: (2)

Ummm, no...that's not how a booster works.
Absent a vacuum source the booster cannot multiply your input, the pedal feels very hard but the brakes don't work much at all.

If there's a leak in the vac line, the engine will run poorly due to the large vacuum leak.

djweej

can you feel if the brakes are locking in the front or rear? both? a booster works off of vacuum. ^ hes right if there was a hole in the line the booster would not function properly and the engine would run like ****. there is also an adjust for the pedal to be in or out. if it is pushed to far in the booster cannot create enought pressure. also if by chance your primary seal in your master cylinder is leaking it will fill the booster with liquid causing poor functioning

Mez

Judging by heat discoloration in both front and rear brakes i am asuming that both front and rear brakes are locking up. i am pretty sure i do have a small vacuum leak but the problem isnt the brakes booster not working its the brake randomly engaging without even touching the brakes. most of the time i will just be driving on the highway or something and the car will start to slow down and the brakes slowly clamp on harder and harder until i cant move without dumping the clutch in first gear. at this point i kick the pedal and try rocking the car back and forth until i am free or if this doesnt work i just leave it and usally the next time i try to move it its free again.

Mez

just checked the check valve and it works air can only go to the engine. i didn't take the caliper off to see if the pistons move freely but since my brakes work normally until they jam is it necessary?

wrankin

There are too many issues here - take it to a mechanic. Explain your issues. Have him flush the brakes, check the callipers for seized pistons, check the emergency brake cable and look at the brake booster vacuum. If the pads have material and the rotors are within spec (=thickness), he will not need to replace them (at least not at this point).

Armchair quarterbacking is all nice and good - but these are your brakes and they are the single most important safety system on your car. Get a pro to do the work. Use the opportunity to ask questions from the mechanic and understand how the system works. Ask to be able to stand near the car as he does the work. If they refuse, find another place to do the work for you (and be firm on that).

Good luck,

clokker

iTrader: (2)

This is the exact set of symptoms I had recently after replacing my booster/MC.
I had the input shaft adjusted too long (hence the suggestion in my first post) but if you've confirmed that's not it, then the booster itself is probably failing.

There is an internal valve that releases the vacuum and stops the assist...if the valve fails, the booster acts as though you are constantly applying the pedal- the longer you drive, the more vacuum is stored and the brakes eventually lock solid.

Try this...
Run the car- parked on an incline with the parking brake on- and pump the pedal a few times. After a few minutes the brakes should be locked up and the car won't roll when the ebrake is released.
Now, pull the vac line off the booster, if the brakes instantly free up, my theory is correct and a new booster should fix you up.

If that doesn't work, feel free to call me a moron and cuss freely.
I won't mind.

Mez

were can i find a booster/ get mine rebuilt? cause so far all i have found is one at the dealer for 600$!!! and another one for 300 something and i feel like this can be fixed for less

misterstyx69

iTrader: (142)

I just mentioned this,as I had reversed the check valve and Ya,the brakes were Hard as Hell,and you REALLY had to Push on them to get the car to stop.IT Felt like you had Pedal,but when you pressed the pedal you had Little Effect to stop the car..it was like Manual powered brakes,and frankly Scarey.
..Put up a Wanting To BUY thread on "The Second Gen Parts For Sale Section" and ask for a booster...alot of guys sell almost anything and Everything.So it shouldn't be hard to find...(600 bucks,,Holy Crap....you can get used for roughly 60-75 bucks.).

clokker

iTrader: (2)

Reversing the check valve in essence duplicates a failed booster.
You lose all the input multiplication and the effort required is significant.

BTW, re: your comment about manual brakes...
A system with a bad booster is nothing like a real manual brake system.
If anything, it's analogous to a power steering rack with the pump belt removed...artificially high effort and sluggish response.

A properly designed manual brake system- correct pedal ratio, twin MCs specced to the calipers, is actually quite easy on the leg and can provide very good feedback and response.
Many racers prefer manual over boosted brakes.

Just sayin.

@Mez: PM me...I have several booster/MC combos you can pick from.

satch

iTrader: (1)

Remanufactured brake boosters are available at "Black Dragon Automotive." I believe they cost $100 with a core or $30 more if no core for your 86GXL.

www.BlackDragonAuto.com