calla1231

'89 s15 4wd jimmy, rear ABS
changed rear wheel cylinders, new master cylinder. now no rear brakes. nothing happens with gravity bleed of lines. I've spent the past 2 days pumping the petal and opening and closing valve. please someone help before I take a sledge hammer to it! this is not how I wanted to spend my father's day.

muddog321

I believe the older models had a proportioning valve that had to be centered so look up front on the frame as you follow the brake lines and see - my 89 Suburban did and it had to be manually centered or no fluid would flow to rears.

Anyone with an 89 know for sure?????

calla1231

I can get fliud to come out when I am pumping brakes, but if I just leave it open and let it sit there, nothing will come out.

MT-2500

As Muddog321 said center the safety valve under master cylinder or open a front bleeder and hit brake pedal and let it go over center and shut front off.
Then try bleeding rear brakes.
If all else fails check the rear rubber brake line.
It may be swelled up inside blocking off rear fluid flow

__________________
Remember proper testing gives us the answer to many problems.
MT

calla1231

may be a dumb question, but how do you center it? I've never even heard of that.

MT-2500

There should be a plunger sticking out the end of valve.
May be a rubber dust boot over it.
They make a holding tool to center it.
When is is centered the brake light will go off.
Step on the brake pedal and watch the end of plunger see if it moves one way or the other.
Then catch it half way in and out for center position.
When the switch on it is not grounded that is the center position.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

calla1231

looking at my manual, I have a combination valve, not a proportioning valve.

MT-2500

Not much differance and you also should have a dump valve.

If you got a manual go threw it for the bleeding procedure.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

534BC

Do you know how to bleed the brakes?