Hi Randy,

I came across this condition while hunting down an intermittent noise that seemed to be wheel related. After a drive I found one rear rotor to be warmer than the rest, although not blistering hot as a seized piston might produce. A few weeks after the repair the noise got worse and it became obvious that the culprit was a front wheel bearing.

The piston would retract every time, but only to a certain point and it took more effort than is normal to spin the wheel. I think the blockage was acting as a check valve. It may well have released the pressure over time but I don't know because I pulled the caliper as soon as I found it. The pad was not showing excessive wear.

Both Gerling and ATE calipers have O rings of a rectangular section between the halves. Sometimes they come with the kits and sometimes not. I usually save the new ones and reuse the old unless they're visibly compromised, and have had no leaks in a couple of dozen rebuilds.

regards, Peter