Brake Problem

I have been searching and searching and I havn't read anything that tells me exactally what I need to hear, and you guys have always helped me out.
Ok my problem:
My brakes when I push on them and I'm not getting the same pressure as i was a week ago. Some times I really have to push hard on the pedal just to slow down. I don't seem to be loosing fluid at all.

Any one with Ideas please help me.
Thanks,
-Matt

More pedal effort required, but pedal does not sink or show signs of leakage? Possible bad booster.

Try this first: With engine off, push the pedal a few times to make sure there's no boost left in the booster. Now with foot pushing firmly on the pedal, start the engine. Does the pedal sink a bit and then stop? That means your booster is at least working. Listen for hissing or other odd noises when you push the pedal, and also for changes in engine speed. Either of these can signify a leaky booster.

Another quick test, but one that requires that you be somewhere out of traffic and out of danger, is to get going and then stab the brake fairly hard several times in quick succession. If you're getting enough boost, the brakes should feel pretty much the same each time. If not, you'll find that the pedal effort goes up after the first one or two.

Another test for vacuum leaks: Stop the vehicle, and take your foot off the brake before shutting down the engine. Now go do something for an hour or so. Come back to the vehicle, and without starting the engine, push the brake pedal a few times. If the booster is holding vacuum, you should hear it whoosh a little, and feel some boost for at least a couple of pedal pushes, before the pedal firms up. A good booster should hold vacuum for much longer than that.

If the booster is good, make sure there isn't a leaky hose from the manifold, and that the check valve is not cracked or broken.

If everything with the booster looks good, you should make sure that your front calipers are not getting rusted and stiff, and that your rear brakes are adjusted correctly. Probably not a contributor, but since the rear self-adjusters are a farce and a joke, it doesn't hurt to check anyway.

last time out we had at least 3 tj's with low braking power and after snugging up the rears by hand they all worked great. been several months now and still good to go.....

I bought a Comanche last year and I replaced everything on the brake system, calipers, wheel cyls, everything and the brakes still stunk. The booster passed the tests the above described. But, I broke down and bought a rebuilt one for $78 from O'Reilly's. Fixed. So my suggestion is to verify everything as above, and if brakes are still bad, booster might be good enough to pass tests but....

Thanks guys. I'll try all that. I was noticing that when I push on the break I was getting a squeak from the rear? could that be contributing to the problem or could that be the problem?
-MAtt

Absolutely. I would definately check out everything before the booster, but don't hesitate to buy one, like I did, after everything's in order.$78 was money well spent in my case.

I had the same experience - replaced all pads/shoes and no luck, then bought a new master cylinder and booster (the M/C is only $20 more and you might as well replace it at the same time) and VIOLA! Good as new.

dabeersboys said:

Thanks guys. I'll try all that. I was noticing that when I push on the break I was getting a squeak from the rear? could that be contributing to the problem or could that be the problem?
-MAtt

Click to expand...

A little squeak from the rears is not uncommon, but it is often a sign that it's time to adjust the rear shoes, because they shouldn't be moving very far when they're adjusted right. Extra movement will accentuate the squeak. If you're experiencing odd brake behavior, it's probably a good idea to open up the rears, make sure they're together correctly, not worn out, and that there isn't a leaking slave cylinder. Then adjust them by hand. Even if it doesn't solve the problem you'll have one part of your brakes where it should be.

Ok, So i replaced the Master Cylinder, Bleed it, and the breaks. I have the same problem, and the break light will turn on occasionally. I unpluged the vaccume from the boost and pluged the hose with a bolt and I still had the same problem with having pressure, and not having pressure. Any more Ideas? Please I really need to get this taken care of.
-Matt

dabeersboys said:

Ok, So i replaced the Master Cylinder, Bleed it, and the breaks. I have the same problem, and the break light will turn on occasionally. I unpluged the vaccume from the boost and pluged the hose with a bolt and I still had the same problem with having pressure, and not having pressure. Any more Ideas? Please I really need to get this taken care of.
-Matt

Click to expand...

Based on your first post I would say it is the brake booster (internal vacuum leak) or a leaking vacuum connection at the booster, but a leaking vacuum anywhere would cause a high idle. Years ago, on a Dodge I had the booster slowly went bad, it got bad enough that I could hear the vacuum leak inside.

I would inspect all four brake wheels first, repair if and as needed, then consider the brake booster, but there is also an anti-lock (I think that is what it is called) equalizer sort of valve after the master cylinder that could have gone bad!

UPDATE: Alot of work no results!

OK, So I've about had it. and I'm broke for valentines day. I've inspected everything. No leaks.
What I've done:
Replaced Master Clyinder, Brake Booster, front brake pads, and rear brake hose. I've blead the thing out 7 times, no air. Had it power flushed and bleed. I still have the same problem.
When I break some times I have pressure, some times I dont and It will go to the floor and I can lock my wheels. I don't know what else to do? Maybe re- replace the master cylinder?
I am leaving on friday for a ski trip and I really need to get this fixed! any Ideas PLEASE!!!!
-Matt

Re: UPDATE: Alot of work no results!

dabeersboys said:

OK, So I've about had it. and I'm broke for valentines day. I've inspected everything. No leaks.
What I've done:
Replaced Master Clyinder, Brake Booster, front brake pads, and rear brake hose. I've blead the thing out 7 times, no air. Had it power flushed and bleed. I still have the same problem.
When I break some times I have pressure, some times I dont and It will go to the floor and I can lock my wheels. I don't know what else to do? Maybe re- replace the master cylinder?
I am leaving on friday for a ski trip and I really need to get this fixed! any Ideas PLEASE!!!!
-Matt

Click to expand...

That sounds a lot like the master cylinder. Try this: With engine on, so that there's boost, press down on the pedal slowly, firmly but not too hard. Don't stab it as you would for a panic stop, but press steadily. Does the pedal stay up or slowly sink? If there's no leak anywhere, a sinking pedal means a bad master cylinder.

One other thing worth checking, which can cause a randomly low pedal, is a very bad wheel bearing that is causing a rotor to wobble enough to push the caliper piston too far in. This can be inconsistent, depending on what cornering forces have pushed on the rotor.

But it's important for diagnosis and getting advice to make sure we're talking about the same thing. Is the change one of pedal effort, or of pedal height, or both? A bad booster will cause a high, firm pedal with high effort and poor braking effectiveness, but not a sinking pedal.

Can you determine, when the problem occurs, whether or not all four wheels are braking? A failure in one brake circuit will cause a very low pedal, but there will still be some brake at the bottom. Because only one end is doing all the work, the brakes that do work will tend to lock up.

Re: UPDATE: Alot of work no results!

Thanks Matt,
First, the pedal has height, at least it springs as high as it will go, its just really spoungy and doesn't feel like its breaking until almost the bottom. some times it doesn't feel like its breaking at all until very close to the bottom and when I push the pedal to the floor I can feel a click on the pedal, and the brake light lights up. I don't think its a bad booster based upon tests and what you described. Im begining to think it is the master cylinder, or wheel bearings? I think I'll do master first because I have the life time guarentee, then to the bearings.
I'll keep you updated.
-Matt

OK I replaced the Master Cylinder. No changed, but now i'm noticing it onl;y happens when I make hard turns, left or right. So my next step will be to replace my front line. :banghead: :banghead: :banghead:
Matt

Taking turns causes the brake pedal to feel mushy? I'd check bearings before I replaced anything else. If the bearings are bad (loose) the wheel can move laterally outward pushing the caliper piston back inside the caliper housing (as stated earlier in another reply). This makes it necessary for the master cylinder to have to push more fluid to get the piston back out and thus means a longer pedal travel until a firm pedal is achieved.

Tally_XJ said:

Taking turns causes the brake pedal to feel mushy? I'd check bearings before I replaced anything else. If the bearings are bad (loose) the wheel can move laterally outward pushing the caliper piston back inside the caliper housing (as stated earlier in another reply). This makes it necessary for the master cylinder to have to push more fluid to get the piston back out and thus means a longer pedal travel until a firm pedal is achieved.

Click to expand...

X2 - Been there. One bad bearing will do it.

Hey guys thank you all so much!!! The wheel bearing was the problem It was horrible wobble in the wheel, Now my breaks feel SO nice. Thanks again all for the advice. You all have yet to let me down.
-Matt