Spongy Brakes
 

My 85 has really spongy breaks and I just wanted to bounce ideas out and see if what I think is the problem is, is really the problem. The pedal travels about an 1"-1 1/2" before catching hard, I've replaced the master cylinder and the calipers and brake pads so im thinking that its the power booster. I know normally the breaks get harder when the power booster goes out but when I pump the breaks the idle stumbles. This leads me to think that maybe theres a vacuum leak at the seal or something and its not building enough vacuum. Any ideas?

Give it to me. It's 100% broken.

give what to you?

He is saying that your car is broken, so you should just give it to him and don't bother trying to fix it.

Come on Seth, you are no stranger to sarcasm!

I would bet it is the booster. I can look and see if the local yard still has the FB that was there last time.

Also, have you checked the fluid level? What color is the brake fluid? Any leaks at the calipers/hoses?

:rofl:

I understand sarcasm I just didnt think someone would post something so ridiculous and not follow it up with some advice. So i thought maybe he wanted a broken power booster, idk people are weird now he could be one of those hoarders you see on tv.

I just bled the system completely with new fluid, and no leaks. The only other thing I could think of is the proportioning valve cause when I brake real hard it kicks to the right so much that it turns the steering wheel. Yea tell me if its there and what condition its in I need some other stuff too. Thanks.

the reason I dont think its the valve though is the the whole system bleeds fine. Another thing is that I can pump the brakes and it will get better.

I'd only do it to someone local.

Do the brakes feel spongy when the car is off? Usually spongy brakes is air left in the system.

Sounds to me like you have air in the system still, a sticking caliper, or a brake hose that is bad.
Silly question, but does the car have drum or disc on the rear? You didn't specify, just stated that calipers and pads had been replaced.
If the rear is drum, the shoes being a bit out of adjustment will cause the pedal to feel spongy and low on the first try, but will pump up on the second hit.
A bad booster will have no effect on how far the pedal travels, only the effort needed to push the pedal down. The only way a booster can have any effect on pedal travel, is the plunger inside it that actually operates the master cyl. It could be out of adjustment, but that is something normally found only after a replacement booster has been installed.

Oh, and since you say it pulls hard to the right when braking, I'd start by bleeding the hell out of the left front. That caliper is fed directly by the MC, totally bypassing the proportioning valve. The location of the port feeding the LF (bottom front of MC) makes it darned hard to get all the air out if the MC is not fully bench bled prior to installation.

Ill go back and rebleed everything and see what happens. It is drum and I've never taken a look back there so Ill pull off the cover and see if any adjustments need be done. The thought that I have now is it must either be air or serious lack of brakes in the back and that forces more fluid to the right front caliper causing the pull. Thanks roque

Air
 

Parks 80 LS was spungy till we bleed the master cyl again. Now its good and stiff. Does the 85 have a bleeder on the side of the master?

not that im aware of but ill check and see

I'd bet on 1) air in the LF, and possibly 2) rears needing adjusted. The rear self adjusters can freeze up if they are not properly lubed and/or the car sits for a while.

well Im guessing its number 2 now cause I just rebled the MC and all the lines and its still traveling to far before its good stopping power.

Test for brake booster:
Checking without a tester. Check the 3 tests in order.
(1)
1-With engine stopped, depress pedal several times
2-Start engine with pedal depressed
3-The unit is good if the pedal moves down very slightly immediately after the engine starts

(2)
1 start the engine
2- stop the engine after it has run for 1 or 2 minutes
3- Depress the brake pedal by applying normal force
4- the unit is good if the stroke is long the first time the pedal is depressed and becomes shorter as the pedal is depressed repeatedly (as long as rear drum brakes are adjusted properly, to compensate for non-adjusted rears, apply e-brake fully before perfoming this test)

Note If the results of this next test are unsatisfactory, check for damage or improper installation of check valve or vacuum lines. If a problem is found make repairs then repeat test.

(3)
1-Start engine
2-Depress pedal by applying normal force
3- With pedal depressed, stop the engine
4-Keep pedal depressed for ~ 30 seconds
5-The unit is good if there is no change in pedal height.

If it is still pulling to the right, there is something wrong with the left front brake system.
If the pedal is rock hard, check for stuck caliper, wheel cylinder or improperly installed pad.

Now if you ran the master dry and you have air it it that is another issue.
84/85 factory MC's came with bleeders which should work. But there have been exceptions. If it does not you need to do one of these procedures.

1- bench bleed the master either by removing it and doing it in the vise or doing it in the car.
This next one can be done but can be tricky
2- open all 4 bleeders
2a- press the pedal to the floor quickly, hold it there
2b- close all bleeders
2c- release pedal slowly
repeat as needed.
(really helps to have 2 people on this one, can be done by one but is not fun. Trust me I know)

thanks ill def give that a try