Friends 1996 legacy wagon EJ22 auto. Trying to help her fix this cheap.

 

I replaced the MC for her, problem still is the same.

Bled the entire system, all new fluid.

 

The brakes have always been weak, like you can't lock them up by smashing on the pedal.

 

One problem is that I can't get the problem to happen. Brakes are weak though, like i said you can't lock them up. But they do work, but i can't get them to "not work" and have the pedal go to the floor like has happened a couple times.

I would have replaced the MC as well to fix the problem. Since you have bled the system, all should work. If you replaced with a used or rebuilt MC, there is a chance the "new" MC could be defective.

 

Are you finding any rust on the brake lines that is severe enough to cause even minor fluid leak? That could be why the brakes are weak.

Is the brake balance OK? I.e. does it pull to one side or the other on hard braking?

 

I would consider the possibility of something causing intermittent drag and cooking the brakes. (hill holder if it's a 5sp, internally collapsed rubber brake lines acting as a check valve intermittently, etc.)

 

I once had an old BMW which I replaced both front calipers on with rebuilds from Trak auto. I tested the brakes after the repair and they would lock up just fine, nice firm pedal, etc. Drove the car for a week or so, then pulled up to a friend's house and wanted to make a dramatic entrance. Stomped on the brakes as hard as I could and the pedal went to the floor while the car came to a gentle stop. Turns out BOTH front calipers had hairline cracks due to the hamfisted rebuild. The cracks would flex open under forces greater than required to lock the brakes up and the fluid would squirt out! After the stomping induced brake failure, the car "fixed itself" and seemed fine (save for a small puddle of brake fluid under each wheel!) I guess you have to consider freak failures like that.

 

Nathan

Master cylinder failure and brake booster failer almost have the same symptoms.

 

How to test a PBB

 

With the car off pump the brakes 10 times.

Press brake pedal

Start car

Brake pedal should move towards the floor. If it does not the PBB is bad.

Well, Nipper, I'm afraid I'm going to have to disagree with you once again!

 

Loss of boost due to booster failure will cause a hard pedal. Less than normal pedal travel with normal pressure applied.

 

Failure due to a bypass leak in the master cylinder will cause a sinking pedal (or pedal just goes to floor.)

 

I'll admit that a non technical person could lump both of those into "almost no brakes, pedal feels funny" which perhaps is what you're getting at?

 

Nathan

most of what i read seems to suggest hard pedal for power booster. but i have no idea or how to test things. other than leaks i've never seen brake failures other than MC.

most of what i read seems to suggest hard pedal for power booster. but i have no idea or how to test things. other than leaks i've never seen brake failures other than MC.

 

I just posted the test. A bad MC can damage the diaphram on a the PBB. A PBB can be a goofy failure. A test for a bad MC is stand on the brake pedal with all your weight and see if the pedal creeps to the floor.

 

Now for other things to look for.

 

An internally failed brake line

A weeping brake caliper

Glazed brake rotors

Glazed pads

frozen calipers

 

nipper

I just posted the test.

right thanks. i meant i wasn't sure how to test for other things as well.

turned out to be a leaking rear passengers side brake line, the metal line rusted.