Runamuck

I picked this 98Z up and the owner said it had needed a brake bleed before, He got it bled, it was fine. and after sitting the brakes are spongy again.

Well after some testing, it appears the rear brakes are doing nothing. Only the fronts are working. no leaks anywhere, no ABS light, Parking brake does not engage the rears.
Nothing.. absolutely nothing in the rear.


what could this be, I mean i figured ABS, but the manual says the ABS light should be on, if the PCM decides to cut off the rear brakes to what it see's as a malfunction.

WS6exY

Check to see if the rear calipers are getting fluid by opening the bleeder screw u wanna keep that screw open until fluid comes out. If the calipers are getting fluid but the pads are not contacting the rotors to make the vehicle stop then the pistons could be stuck in the caliper, which means u need new ones. The parking brake is gonne be either the cable or the parking brake shoes, which are under the rear rotors if the shoes are below specs the car will still move with the parking brake up! You should also bleed the brakes again to see if it was done right! Since the aren't any leaks u might just have air in the brake lines. Manually bleeding the brakes is the best way to tell if u have air in the lines. Hope this helps

Runamuck

Checked everything over again..

I have fluiod coming from the MC like normal.
Fluid coming from the ABS box like normal.
Just a puff of air coming to the rear brake lines though.

wat!?

I was thinking porportioning valve, but why would air be pushed through?

conan

iTrader: (5)

Have you tried to have some one help you and bleed the rear brakes? (they pump and hold and you crack the bleeder)If air is comming out bleed the hell out of them and see if fluid starts to flow.

twitchtwice

iTrader: (12)

could even be a line lock thats fucked and and stuck on?

9000th01ss

iTrader: (10)

Theres only so much air a brake system can hold. If the MC stays full eventually when all the air comes out fluid will come out and the brakes will work.
All I did on my brakes is let them gravity bleed, tapped the calipers a bit to loosen up any air pockets.

It's been a real long time since I needed another person to help bleed brakes.

Runamuck

so I started Bleeding each caliper individually.. the rear drivers side caliper wont hold a vacuum. I get a ton of air mixed with fluid. Using a stethescope I hear the bubbling coming from with in the caliper.

I have checked the line from the ABS to the caliper with no leaks or damage.
internal failure?

Do I just need a new caliper? should I get a new hose to make sure? remember no visable leak.

9000th01ss

iTrader: (10)

When you use a vacuum device to bleed brakes it sucks air through the threads between the caliper and bleeder screw.

What I do sometimes is take the bleeder screw out and put the hose for mityvac right in the threaded part of the caliper.

Do all this with the MC lid loose.
Once fluid starts, it will remain a steady stream. After the fluid in the MC lowers about 3/8" it should be flushed of everything, put the screw back in and tighten it.

Runamuck

its only one caliper that wont hold vaccum, they were all done the same way, why would this one be any different unless it was messed up in some way

9000th01ss

iTrader: (10)

I can't see it from the internet so I don't know.

Runamuck

Well i did what you said, I'm now not just getting anything from the ABS housing.. the lines in the back are near empty and pumping the brake gets no fluid to the rears.
Which would siggest the ABS is retarded, but I still have no dash lights, all fuses are good.

9000th01ss

iTrader: (10)

So when you first turn the key the light 'test' runs. All the abs and brake lights come on then shut off?
I ask because the previous owner could have removed a bulb so the light would stay off for the sale.

As far as bleeding the brakes, you should start at all bleeders close to the MC and work your way further down the lines.
It wouldn't hurt, since you already have air in the abs block, to loosen the lines to the MC and let fluid run out for a second. Then bleed the abs, then the calipers.

I never ran and abs unit dry so you may need to do something special with that, like cycle the key or something I forgot.

chavez885

iTrader: (12)

If the ABS has air in it, it will require the GM tech 2 scan tool to engage it. Usually dealers are the only ones with these. There might be bleeder screws on the ABS if you're lucky those might work. Also when you bleed, make sure to bleed furthest from the Master Cylinder. So Rear Right, Rear Left,Front Right, Front Left.

If that one caliper does not hold vacuum it sounds like it is damaged somewhere. The cheapest solution would be to pick up another caliper or rebuild the caliper and try re-bleeding. Also you could try bleeding the old fashion way or with a motive power bleeder (60$ godsend). To me it sounds like that caliper is bad.

9000th01ss

iTrader: (10)

I wouldn't replace the caliper yet. If you had a leak big enough to hear vacuum, eventually it's going to pour fluid. I think you're hearing air coming from the threads of the bleeder screw.

For the abs unit and tech II tool, I read somewhere how to get it done without that, I didn't need to read it so I don't remember much about it.
If I find that info I'll let you know.
What year is it again?

Runamuck

It's a 98.

and an Update.

The ABS is not working at All. Nothing. I have full manual Front brakes, and no rear brakes, no ABS and no working wanring lights for ABS. I checked the two fuses that have ABS on them, and they were good.

without spending 180$ to have a tech2 hooked up to tell me this **** is bananas, what in the world is going on. Is My ABS unit ****? thats not too normal for any car.