Jeep_junkie

My 1994 TA's rear brakes started acting up a few days ago, gradually losing grip until a couple of nights back I had to make a panic stop and they went out totally with a pop that I could feel in the brake pedal. The e-brake warning light came on, which my mechanic explained was probably because the master cylinder was not developing enough pressure in the rear brake circuit causing the proportioning valve to completely cut that circuit off. Tested the rear brakes with the wheels off the ground and sure enough they don't work. Didn't find any leaks under the car either while I was there.

I put a new master cylinder on it today (bench bled it first), but the problem still persists. The warning light is still on and the rear brakes are still not working. Do I need to somehow reset the proportioning valve so that it allows pressure to go to the rear brake circuit too? I doubt there's any air in the system as the pedal is firm and doesn't rise if i pump it.

Jeep_junkie

7 views and no replies? Come on guys, someone's gotta know something about this.

OK, I talked to a mechanic and he said that the proportioning valve would have to be reset by having helper stomp the brake pedal real hard while the bleeders on the front calipers are cracked open. Tried that and still no rear brakes, warning light is still on. Bled the ABS block in the same way too. It purged a little air but still no rear brakes.

chavez885

iTrader: (12)

Have you considered that it may be something other than this "proportioning valve". Is it BOTH brakes or just one of the rears? I would think maybe you have a stuck caliper? Doubtful you have two bad ones though.

Jeep_junkie

Everything points to the proportioning valve, aka combination valve, which is part of the ABS block. I tested the rear brakes with the wheels off the ground. Neither side comes to a stop even at idle when I press on the brake pedal.

Luckyc

Did you ever resolve? Unstuck the combination valve

Jeep_junkie

Yes, it was the prop valve. The built in safety valve was stuck closed, blocking off line pressure to the rear brake circuit. You're "supposed" to be able to press the brake pedal really hard and reset it but I had to take it to a shop that disassembled and freed the stuck valve.

Luckyc

Thank you, ya thinkin is same for me, appreciate the response.