More than a year ago I installed disc rear brakes and a hydro booster unit. During the install I accidentally put p/s fluid in the brake m/cylinder. I caught it quickly, replaced the master, the front calipers and hoses. I didn't think enough got into system to affect the rears.

Five months pass and the brakes start self applying! yes, w/o touching the pedal. I have to pull over and shut off engine for 3 minutes when I feel the brakes start to drag or after about 3 minutes of driving when it is happening, the brakes lock.

Today I replaced the hydro thinking it was a j/y unit, but now with the new one the problem persists. I need to make it happen, then jack up the vehicle with it still running, and determine which wheel(s) it is happening with.

Any ideas???

 

Well, I'm no expert, but there is no way no how power steering fluid getting into your brakes is gonna make them lock up on their own. I've heard of guys using beer or urine to fill a master cylinder in a pinch. Sounds like you have something plumbed wrong or your just fishing and I'm gullible.

 

Ive seen this a few years ago with a torino it was the plunger in the master so check that

 

P/s fluid makes rubber swell, like all the seals in the master, wheel cylinders or calipers, and hoses. Pressure get through but won't be allowed out. Pressure builds. That is a fact. Beer or urine won't do that. Do a google search for 'power steering fluid in brakes,' and read about guys having to replace every bit of their brakes b/c of the problem.

 

Sorry got in from the shop late after a few celebratory beers when I got the hydroboost done. Learn something new everyday, usually before I step on my d1ck. Haha

 

Something is acting on your entire system not just front brakes or rear? I would suspect master or what about your proportioning valve? Do you have a stock one? I'd suggest an adjustable wilwood or something similar.

 

Everything is new, with an adjustable p.valve. I accidentally put p/s fluid in m.cylinder and caught it w/in hours. Replaced master and front calipers and front lines.

It ran for 5 months great. Then the pedal started feeling like the free play was getting less with in 10 minutes of running. When that happens I have to pull over and shut it off for about 3 minutes, or breaks lock up. After 3 minutes wait, it is fine may not do it again all day; or it may once or twice that day.

I just spoke with a brake tech where I bought some of my system. All components need to be replaced (again!!), mater to rotors on all four, all rubber lines, residual valves, calipers, and p.valve! Frickin' A.