first off i would like to thank everyone who took the time to read and reply to my first post. i appreciate all your suggestions and offers to help find parts.
but, before i spend any money or bolt on any rare parts, i have a situation that still hasn't been resolved and i need some opinions as to what the problem is.

after my o.e. proportioning valve messed up. i tried to find a new one, but , wasn't able to. i went to the junkyard and pulled one off of a 1976 olds 98 that had front disc and rear drums like mine. unfortunately i kept getting pressure building up at the calipers. the pads start rubbing the warped rotor and i get vibration at highway speeds, and just plain resistance at slow speeds (like i've got one foot on the brake). the more i use the brakes the worse it gets

i took the one off my eldorado, which is a nice brass one that i bought new a few years ago, and put it on my 98.

i'm still having the same problem with this valve. the only remedy seems to be to pull over and open the bleeder screws to release the pressure build up.
overnight or over course of the workday the pressure bleeds off on its own.

does anyone have ideas? i find it hard to believe that i've had three proportioning valves in a row go bad.

thanks,
john

 

Im sorry if this has been covered, I didn't see your first post but are you sure its the proportioning valve? How old are the rubber lines? Rubber lines will begin to collapse internally and cause the exact same symptoms.

 

Jthw8 is right some times the hoses get worn inside and causes like a flapper valve that when you put pressure on the brakes it holds the calipers closed ,when you release it at bleed off screw it would only be until you put pressure on them again , is it doing this on both sides ? if not it could be the master cylinder is not working right and needs to be adjusted so the pressure is right to the front and rear brakes .

rocwal
Dan B

 

I'd bet on the rubber hoses as well.
Sometimes they won't even let pressure back at all and your wheel locks up.

 

We had this problem in a 96 chev pickup, we originally thought the problem was the ABS well it wasn't it was the master cylinder was not releasing and the front brakes were locking up,if we bled off the master the brakes worked fine.After we replaced the master cylinder the brake system worked just fine.Try rebuilding or replacing the master.I personally had never heard of this happening before,until it happened to a friend of mine.

 

This same thing happend to the right front caliper on my old Ford... I never knew until i changed the brakes - I found a 1/8" deep groove in the back side of the rotor from the pad lining rivets. Changed both hoses, turned the rotors and has worked fine for 15K miles now... My rotors will prolly need changing at my next brake job, as they are close to the safe limit...

 

wow, i didn't know the hoses could do that, as far as i know they are original. the car sat in someones dusty garage for 14 years before i bought it.
the weather is supposed to warm up this weekend, i'm working in the driveway, so i'll start with the hoses.
thanks everybody!!
john

 

If you are going to replace the hoses then might I suggest you go a little bit more $$$ and get some braided stainless ones?

These are made for almost every GM car and are not that much more than rubber ones. They are braided stainlesss on the outside and nylon tube on the inside and will NEVER swell up on you.

They look cool, too.

 

I think i would do some research on the braided hoses from someone that has used them for a long time, somewhere i read an article about them not being so great , they are for show ,ANYBODY some thoughts ???

rocwal
Dan B

 

That is a good point about them being for show. Like anything else you can get high quality or low quality, but high quality ones will last better than rubber hose and will not swell. The low quality ones are just for show.

It pays to be a wise shopper when you are buying brake parts.

 

The braided stainless lines we use in aerospace applications are decidedly NOT for show. Aerospace grade teflon lined braided brake lines will swell less than rubber and will last much longer.