Newbie here

I have a 1994 Dodge Grand Caravan LE with a 3.3L engine. No ABS. The issue I have is the front calipers randomly are not releasing front rotors. Usually only 1 gets hot & sticks. Gas mileage has dropped. Happened multiple times, randomnly, on either side. I have replaced the calipers, rotors, pads and one suspected rubber brake line. Had entire system professionly power flushed and bled. Good for one day. Next day, road trip, colder, B_O_T_H calipers stick to the point where car wont move. Get hot. Some smoke. Break bleeder valve to release & drive home with parking brake in snow. Very fun.

Think it is the master cylinder. However, I believe the caravan hydraulic brake lines put the front calipers on different hydraulic circuits. They cross to the rear drums. Meaning a failure on both calipers (sticking - fluid trapped) would have to happen at same time on both circuits. Would a bad master cylinder (proportioning valve?) prevent fluid return on both circuits at same time? Seems unlikely. Thinking it might be the vacuum boost unit, because when I originally replaced all the brake parts myself, I could not get pedal firm up. Following morning, pedal was very hard to press, but brakes seemed to work. But eventually seized up again. Then did pro mechanic flush & bleed. And it did it again!

So that's the dilemma. Am trying to determine, from symptoms described above if its master cylinder ($40) or vacuum boost ($200)

Any thoughts would be appreciated

Dave in East Aurora, NY

 

I can't see a vacuum booster ever causing that issue. You are correct, the system is crossed, LF and RR, RF and LR. If there is enough crap in the system, it could cause the master to stick in both chambers so I would be more inclinded to start there. I would also replace the other rubber hose.

 

Thanks Tizzy - thats all I needed was a push in a direction. Appreciate the input

Dave in East Aurora, NY (currently getting slammed with snow ;-)

 

Still doesn't make alot of sense, you would think the rears would also be sticking but they are drum so maybe not applying that great.

 

Agree. They may be "locking", but as you say, not as much. I believe there is also a height adjustment valve near each drum that modulates the rear braking pressure based on the list of the vehicle. Think its connected to the suspension. Whats interesting, is that I added spring boosters to the worn out leaf springs. I guess drum brakes apply more stopping pressure vs discs for the same amount of hydraulic pressure. So they need to be cranked down some so the front discs do most of the work.

Was also lead to believe that the master cylinder gasket was responsible for applying reverse pressure to the hydraulic lines so the fluid would be sucked back in. My gaskets were original and had holes, so thought that was the culprit. Replaced, but had no effect.

After reading up a bit on this, one realizes that the design of effective brakes is quite complicated.

Dave in East Aurora, NY

 

Update. Had the master cylinder replaced, other rubber brake line, and professionally flushed and bled. Drive around town for several days, seems fine. Checking by placing hand on hub caps and checking for heat.

Hit the road to drive from NY to NC, 25 miles out, hilly driving at 60mph, stop to check, and left front caliper is much warmer and emitting essence of toasted brake pad.

I am clueless. After replacing all components of the brake system except proportioning valve, vacuum assist and metal brake lines, Im still having front caliper problems.

Is there any chance leaf spring boosters I added could be affecting the proportioning valve, and putting too much pressure to the front brakes? Dont know what else to do.

Dave (still) in East Aurora, NY

 

Brakes get hot, especially on hilly terrane. Possible you fixed it and you're just paranoid. As far as the rear valve, I doubt it, my '93 is stuck, kinda weird to drive on ice but otherwise no front brake issues.