symptoms of a failing proportioning valve??

[Andylad13]

anyone experience this before?? how do they fail, and what do they act like when failing?

reason why i ask....

i have replaced everything, and i mean everything short of brake lines, in the brake system, and ever since day one with the truck the passanger side rear wheel locks up when i brake. locks up on gravel, and pavement if i stop hard enough. and she squeeks, new pads last about 2 weeks then they start squeeking too. everythings new except the proportioning valve. think it could be stuck open or something, sending more pressure to the rear????

 

[LCAM-01XA]

The prob valve splits the system front-rear, there ain't no side-to-side pressure differentiation from it. I think your right rear brake is adjusted too tight, or keeps tightening itself more than it should - pull the drum and inspect the self-adjuster hardware. Mine is like that on the left side, but I know tis a bit on the tight side, down at Toledo Speedway in the pits it would lock and slide all over the place, I tightened the right side and now they lock up equally, lol, but I'm sorta used to it.

 

[Andylad13]

yeah i checked that, i know that there isnt side to side pressure, but the tires are crappier on the side that locks up, so if there was more pressure going to the rear, then that side would lock up sooner due to the harder, and more worn rubber.

i checked the hardware, loosened the selfadjuster, for some reason it just keeps overtightening.

but what your saying is there isnt a way for the valve to do what im thinking of?

 

[LCAM-01XA]

Switch some tires around, move one of the crappy ones to the inboard location of the left side, so you end up with good tires on the outside and the bad ones on the inside, that should help a bit. On your question about the prop valve - my '90 ain't even gone one, tis all done inside the master cylinder I think, all I have is a line from the master to the RABS, and then another line from the RABS back to the axle. Compared to that my buddy Jake's '86 F250 has load-sensing brake bias valve before the rear axle, makes for less pressure when empty but ramps it up as the truck gets loaded and the rear sags. He may or may not have a prop valve, not sure of that, but his tires never lock up, and he can stop just as fast as me.

 

[hotford]

Mine has done the same thing, so please let me know what you find out.

 

[tknomaj]

locking up

the reason it is locking up and adjusting it's self too tight is you have a drum that it out of round remove drum and mic it to see if it is in spec if so turn it but it may come back sure fix is to replace it and problem solved P.S. no chinese c--p and you will be fine

 

[LCAM-01XA]

Actually after seeing some good Chinese manufacturing I think if there's one thing the they know how to do that is to cast iron. That, and have fun finding rotors and drums that are nod made overseas, if it ain't China tis India, same difference really. But you do have a valid point about drums being out of round, it's something worth checking at least.

 

[tknomaj]

I replace brakes on cars and truck everyday and chinese drums and rotors are fine for grandma or if customer can afford nothing else but one-half of chinese products installed have to be replaced because they do not stay true even after being turned !

 

[Dsl_Dog_Treat]

Well let me throw this out. I had the same experience and was chasing parts and eating shoes on the left as well. Here's what I discovered.......

The inner axle shaft bearing was failing and caused the axle shaft to vibrate. The vibrations caused the adjusters to constantly adjust eating up the brake shoes. I was having to release the adjusters on an almost daily basis till I swapped out the rear end.

I could take a screw driver and pry the inner side of the drivers side axle shaft and move it almost 1/8 of an inch at the inner bearing on the punkin.

Might be worth popping off the rear diff cover and take a peek.

 

[tknomaj]

thats possible have never seen it and what you say is correct it would make same results but i have seen bad drums all the time thanks you gave something to think about

 

[LCAM-01XA]

I replace brakes on cars and truck everyday and chinese drums and rotors are fine for grandma or if customer can afford nothing else but one-half of chinese products installed have to be replaced because they do not stay true even after being turned !

Oh yeah, low cost is low quality for sure, you get what you pay for with auto parts. I'm just saying the Chinese can make some decent parts, now whether someone cares to import them here is a whole another issue - my experience has been that usually the OEMs use those, but that's it, chain stores go for the cheap ****.

 

[hesutton]

I've also had this happen when the outter axle seal leaks gear oil from the axle tube into the brake mechanism and drum. It gummed everything up and it would lock up with only slight peddle pressure. I got some crazy looks and a couple of "NY City Hello's" flipa) at each stop light.


Heath

 

[Andylad13]

ok, ill try swapping the drums from right to left, and if my left starts locking, then ill replace the drums.....AGAIN! but it would be worth it if that was the problem. as for the seals, all is dry, but if this doesnt work, i may just pull the diff cover and inspect tolerances.

 

[94johnh]

I had this problem several years ago.went through 2 sets of right brakes.
the last time I bought the small parts kit from napa and replaced everthing in there.Self adjustor and all. No problems since(2 years). worth a try!


john

 

[subway]

odd if it was the proportioning valvle it would lock both sides if anything. both sides are fed with the same rubber line so they SHOULD be completely equal. I assume the system has been bleed well if you replaced parts so there is no flow restriction (kinked, crap in there) in the lines.

same thing could happen thogh if one of the wheel cylinders was stick, all the pressure would go to the other side.