Hey all, so I thought my brakes on my '91 Z28 were working fine - firm pedal, stops pretty well. But when I have the back end in the air and idleing the brakes can't hold the rear wheels from turning. Since the rear disks and pads are good and the calipers don't seem to be sticking, I suspected the MC as the culprit and replaced it. Made no difference. Would the proportioning valve be the next thing to swap out?

If so, the dealer wants over $100 for a new one, is there a less expensive source for a new part without having to deal with all that adjust-it-yourself ratio stuff?

Thanks!

never know but rear flex hose could be collapsed internally, they had a recall on them anyways on some of our cars. im repalcing mine on my 84 Z28 soon sine its one of those cars and the rear brakes werent working very well at all.,,

good luck

If you're going to replace anyway, you might consider braided steel lines from Earl's or Russell's.

JamesC

I haven't seen anything on a recall for a 1991. How would I know if it had collapsed internally? Is the 'flex' hose the main line that goes to the rear or one/both of the ones that travel to each wheel?

the rubber hose from chassis to axle housing wjere the two axle lines screw into, they can collapse internally, sometiems that is the culprit, sometimes..

I noticed the same thing - tires spinning when car is raised and the pedal brake is applied).

I have NO PROBLEMS with the system while actually Driving the car....... I upgraded to the aluminum caliper set-up from 89 up & the cars stops great !

In my case - The whole rear braking system was replaced. I used a new line from the Master cylider back to the rubber line,...... a new rubber line, new steel lines on the axle, and brand new pads on each caliper. My rotors are not new - but there is plenty of meat on them.

At first I thought that I might still have air in the brakes lines - but after bleeding about a 1/2 pint of fluid from each caliper I figured that was not the reason !

This might not be a problem ----->

I am wondering if that little bit of "play" is supposed to be there,..... allowing for the parking brake to take up the rest of the slack when it's used.

*I'll test that theory the next time the rear wheels are off the car !

I noticed the same thing - tires spinning when car is raised and the pedal brake is applied).

I have NO PROBLEMS with the system while actually Driving the car....... I upgraded to the aluminum caliper set-up from 89 up & the cars stops great !

In my case - The whole rear braking system was replaced. I used a new line from the Master cylinder back to the rubber line,...... a new rubber line, new steel lines on the axle, and brand new pads on each caliper. My rotors are not new - but there is plenty of meat on them.

At first I thought that I might still have air in the brakes lines - but after bleeding about a 1/2 pint of fluid from each caliper I figured that was not the reason !

This might not be a problem ----->

I am wondering if that little bit of "play" is supposed to be there,..... allowing for the parking brake to take up the rest of the slack when it's used.

*I'll test that theory the next time the rear wheels are off the car !

Wow, very interesting! I haven't gone replacing anything else yet and since you've already replaced everything and still have the 'problem'... well let me know what you find out!!

I found these posts last night after writing my thread:

https://www.thirdgen.org/techbb2/sho...rtioning+valve


https://www.thirdgen.org/techbb2/sho...rtioning+valve


They seem to be 2 different ways of *fixing* the weak rear brakes !!!

I'm going to try the "washer" method first since I will not need to bleed the brakes. If that doesn't work well for me I'll try the "removal" trick !! (some people have said the rear brakes are locking to soon when the piston and spring are removed)


Good luck !!

I'll give the washer method a try first too. Thanks!

Let us know how the "Washer" method works for you guys.

Oh yeah,
When I swapped all my brake stuff from my doner car I wound up with a left front brake hose with internal blockage.
It's noticeable when you bleed the brakes. Instead of a substantial rush of fluid when brakes are applied, you'll only get a trickle, also pushing the piston back into the caliper will be a lot harder than normal.

What was the cause & resolution of the left front brake line internal blockage ???

Age I suppose. It was 15 years old.
Bought new front hoses at Autozone.
Don't remember exactly how much they costs, but it was abt $30 for both hoses. I remember one costs a little more than the other for some reason.

That's odd. If you've got the PBR rear brakes, they *should* work good. I know for a fact my e-brake will STALL my ZZ4 if I apply it in 1st gear at idle on the stands, if the clutch is not disengaging.

My E-brake doesn't doesn't do much of anything, although I haven't looked into adjusting it. With the rear end in the air and my foot firmly on the brake pedal, if i pull the ebrake all the way the wheels will slow to a near stop, but still keep turning. The car's a '91, so I'm assuming it has the PBR rear disks.