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Brake Pedal

J

jeepsrock

NAXJA Forum User
Location
LA California
Its kinda strange i am not really complaining but rather checking out the issue --my brake pedal is very hard to push in the morning until i start the car. Before i worked on my brakes recently, the pedal was loose and i could pump the brake with each consequtive push getting harder when the car was off. Now the brake pedal is very stiff and if i push hard i can possibly get a simple pump out of it. But once i start the jeep the the pedal goes down like it should and everything functions like it should.

Should i be worried or is this good ?


pete
 
If brake function is otherwise normal with the engine running, it sounds like you have lost the vacuum check valve. Look at the brake booster (the big round thingy the master cylinder is bolted to) and look for the vacuum line on the passenger side of the thing. The little elbow is the check valve, and should be available in the "HELP!" section of the local for a few dollars. It's just pressed into a rubber grommet.

One quick way to check is to run the engine at idle for a bit, and kill the engine. Listen at the grommet for a leak - if there is an audible leak, you have probably lost the grommet. If there isn't, it's likely the check valve.

Given a choice, change both. You should be able to get the valve and grommet for less than $10 total outlay, and replace them in about 20 minutes. I only say that long because they're really in there, and will take some work to change...

5-90
 
Additionally wouldnt this cause the brake pedal initially to be able to be depressed when the jeep is off but it would be rather hard, bc i dont think this is th prob as i feel a pressure that doesnt allow me to press.

pete
 
jeepsrock said:
But if the brake check valve was busted wouldnt the braking be very hard when the car was on also ?

pete
Click to expand...

Not necessarily. If the check valve is no longer "checking" (is now allowing flow both ways) you will get brake function while the engine is running, since there is an active source of vacuum. The idea behind the check valve is to retain vacuum in the booster so you can have brakes if you are running at WOT for a while or if you need to stop after your enging decides to pop off for a biscuit. As long as the system is otherwise sealed, your brakes should work normally with the engine running (which is why I suspect the check valve first.) Changing the grommet while you're in there is just a good idea - you've got it exposed anyhow.

Make sense?

5-90
 
What 5-90 said.

You're losing vacuum. Could be the check valve, could be a loose hose somewhere.
 
i will take a look at the check valve as i have another one from another booster from a cherokee.

Can one test it using their mouths or is it much higher pressure ?

pete
 
Well basically i still have the same issue. After i installed the check valve and gromet i can push the pedal a few times after the engine is shut off right after the car is off, but if i wait more than a few hours its rock hard stiff and cant be pushed...Otherwise the brakes work well, but its pissing me off...any ideas ?????

pete
 
Then it's probably the booster itself that's leaking - either a very small pinhole in the diaphragm or the seal where the two shell halves come together.

I'd keep it in mind, but you should be fine until you start noticing loss of braking at freeway speeds (when vacuum is minimal.) You're probably going to be replacing a booster sometime in the future...

5-90
 
This is very strange situation bc i originally put in this booster off a junked 93 which was working when pulled into my 94 which was hissing. Once it was put it didnt hiss but also has this stiff pedal when off issue. Other than replacing the check valve which i have done do you have any other sugestions....anything even ghetto.

pete
 
You know not to bother anyone else with this issue but i was thinking about it and thought to myself..if the booster was leaking then it would get stiff when the engine was off but the pedal would be pushable. Unfortunately thats not the case the pedal is almost impossible to be pushed ??

pete
 
From the manual:

Excessive Pedal Effort
Malfunctioning power unit
Partial system failure
Worn disc pad or lining
Caliper piston stuck or sluggish
Master cylinder piston stuck
Brake fade due to incorrect pads for linings
Linings or pads glazed
Worn drims
 
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