The Stovebolt Site Forums The Shop Area General Truck Talk Dorman master cylinder rebuild kit warning!

I rebuilt the master on my '65 and it leaked. Took it apart and found out the rear (outermost) piston cup seal just slipped on over the aluminum piston loosely. The brakes were fine but it leaked fluid out of the boot onto the firewall, maybe 1/8" of the reservoir level a day.

Anyway, I guess the moral is ALWAYS check Chinese crap well before installation, and avoid it if ya' can. Now I have to go buy another kit and put it back together. And the brake fluid also ate some paint off the firewall. Nice.

-Chaz

i'm sure you checked to make sure it's not backwards. wouldn't think it could slip much as long as it is the correct bore rubber cup and the bore isn't too wore. i do hate those tapered pig tail type springs they include anymore, the ends aren't as wide as originals.

It isn't loose in the bore, it's loose on the aluminum piston it fits on/over, and leaks between the two. It's the seal on the piston closest to where the master cylinder bolts to the firewall.