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???

 

If you get on some ice, snow, sand, loose gravel, that should give you a good idea.

I don't know if you eliminated the residual valve when you converted to rear disks, also the porportioning part of the combination valve. As you know oil will swell all the brake rubber including the inside of the hoses.
Might be easier and faster just to rebuild the rear calipers and replace the hoses. Should be able to clean up the prop valve. Flush with alcohol.

 

Of course all the hoses and calipers are new. Ouch. I was hoping to avoid the expense
of replacing them again. I was told by ABS brake to add a 3lb residual valve to the rear discs, and I did. Is there something inside the residual that could be affected by the p/s fluid?

The prop. valve is a new aftermarket adjustable. Thx.

 

Most residual valves are just a little rubber flapper.
Never heard of using oem with all disc brakes. They were for front dis/rear drum or if the master was below the calipers. Corvettes never ever came with them with discs.
Purpose was to keep the drum shoes close to the drum, not needed with discs because they slightly rub all the time.

That's all I know

 

Thx. If the residual v. has a rubber flap, then maybe it is the problem--swelling from the p/s contamination.

 

You should only need to run a residual valve if the master cylinder is lower then your calipers.

 

Thanks. Somewhere I have a line swelling and making my brakes come on by them selves.

 

Just spoke to a brake specialist where I bought my system. He said I need to replace entire system, again!! I may cry.

 

Thats so lame, I just priced out all the parts that need to be replaced on the setup I just tore off my 79f250 so I can convert my 72 to front power disk and I'm looking at $200. I could only imagine how much you spent and the time put into that setup so to be honest I think I would cry if I were in your shoes...

 

Entire as in Master, all valves, rubber lines and calipers? OUCH!

 

Price shouldn't be that bad. I can get the hoses at Rock Auto for about $5-7 ea., and the kits to rebuild the cals are about $4 rears, and $8 front. The master, if needed, is under warranty, so the only item that costs anything is the p.valve @ $50.

 

Thats not bad, time consuming so it sucks but not bad as far as the cost is concerned. The thing thats breaking my bank is the kingpins, they're not cheap and the old ones aren't going on my truck considering they're in worse shape then the older ones that are currently on it...

 

The truck sat since Sun. evening. Tues. morning I move it and the brakes bottom out, giving me 1/10 the stopping power, hardly will stop it in parking situation. Where the heck did this come from?

 

Well I have officially been convinced to just replace all my breaking w/oem parts! Rear drums for life.

 

I am going to remove the caddy ebrake calipers and install the ones everyone uses: 75 Chevy K20 4X front calipers. Wow, they should actually fit my rotors now since I'm using those rotors too. They're dirt cheap too.

I'm going to shut down the rear with the adj. prop. valve, and drive it. That will tell me if there was any contamination damage in the rear system.