RWABS Causing New Wheel Cylinder Blowout?
 

92 Dak...Replaced the rear wheel cylinders. After bleeding same, pressed brake pedal a few times to seat the shoes. Noted brake fluid running from behind drum. Took drum off and primary side of new wheel cylinder piston and the seal around it had blown off of wheel cylinder. Had to disconnect brake line from cylinder to get primary shoe back to position. ABS light was on too. Thinkin replace left rear hose assembly and ABS? Or would a bad ABS module misdirect too much pressure to left rear cylinder, so just replace the RWABS unit?

I'm wondering if, by chance, the wheel cylinders you installed were for the smaller, 9" drums, instead of 10" drums? Just thinking that the cylinders for the smaller drums might be "blown out" by extending too far in the larger drums. Don't know that this would actually be the case, but it's the first thing that popped into my head.

By the way, I believe the 4 cylinder trucks had the 9" drums, while the 3.9 and 5.2 had the 10".

Advance Auto sold me these wheel cylinders and I did tell them she has 10 inch brakes

Are you sure you had the brakes assembled and adjusted correctly? It sounds like the adjusters were not in properly (or way out of adjustment) and allowed the shoes to push on around.

Checked brake installation and all was correct. Adjusters on the correct side (relined brake assemblies one side at a time) and both set all the way retracted. Right side cylinder worked perfectly. When weather warms, going to put it together again after cleaning brake fluid off of parts. Currently cylinder disconnected and brake line capped. Thank you for the reply!

Long shot, but is there any chance the piston was left out of the cylinder? Other then that, assuming all was assembled correctly and the correct parts, I don't see how its possible. Good luck and let us know what you find.

Never thought of that, but its a new wheel cylinder...bad weather here is keeping me from working on it now. I will check that out and advise. That brake line is capped off, so other brakes are working fine. Thank you again!

RWAL won't cause that at all.
ABS doesn't increase pressure it just turns it on and off.


If it's leaking... either the wheel cylinder is fubar or cylinder and shoes were adjusted/installed wrong.
(or it's leaking before the cylinder someplace)

Just because a part is new doesn't mean it won't fail.
We get bad parts from time to time in the shop.
They make a bazilion parts, odds are some end up bad.

Brakes, hardware, et al, installed correctly. My original thought was the ABS system is sending too much pressure to that cylinder�� ABS and brake lights have been on since I got her running again, after she blew original engine. Figure all that downtime allowed time for the hydraulic units to internally corrode. Have drained and flushed brake fluid and "centered" the hydraulic modual.
Yes, could be a defective wheel cylinder....I've seen new parts fail too. Better weather coming so I will dig deeper and advise. Thank you for the reply!