Rear brake caliper question, outer adjuster appears to be leaking, will not tighten to set clearance Options

[DRPHIL914]

my calipers were all fully restored by PMB performance around
5 years ago of so, when we did all new hard and soft lines. The whole system was replaced then, and i check and set clearance yearly. last year i had to do a new master cylinder so i did that ans set the clearance right before Werks Reunion last May.
now it’s time again and i noticed when i pulled the wheel there is a very small amount of fluid leakage around that outer adjuster, and after i loosened the lock but i turned the inter adjuster but it didn’t tighten up the pad at all it just spins! there is way too much space there and it needs to be in quite a bit.

any thoughts here? am i going to need to send this in?

@EricShea

[PatMc]

If fluid is leaking past the outer adjuster...the seal between the small o-ring on the adjuster and the caliper body has failed...that doesn't necessarily mean the o-ring is bad, but possibly the sealing surface of the outer caliper body or the adjuster shaft could be degraded such that the o-ring simply can't seal. The outer o-ring is pretty small and there isn't a lot of allowance for dimension deviation. We scrap a lot of outer half castings that are too far gone, even though they'd probably pass the pressure test.

As far as the inner adjuster not doing anything...keep in mind you're turning a gear, which in turn drives the adjuster. If you spin the gear clockwise, the adjuster shaft is spinning counterclockwise attempting to draw the piston back away from the rotor. Once you hit the limit of travel, everything will just spin. If the piston is sticking in the bore, it's possible the mechanism has pulled out of the piston...try running the inboard adjuster clockwise to run the piston out until it starts moving, then grab some channelocks or a clamp or something and without turning the inboard adjust, try and squeeze the piston in to re-seat it over the adjuster mechanism.

That being said....if the outer adjuster is leaking, the calipers will have to come apart for, at the very least, a cleaning....but it's likely the o-ring was rolled during installation or stuck at some point and was subsequently damaged upon a recent attempt to adjust the outer piston.

End of the day, those calipers should be rebuilt or exchanged for a set of quality rebuilt units...

[DRPHIL914]

If fluid is leaking past the outer adjuster...the seal between the small o-ring on the adjuster and the caliper body has failed...that doesn't necessarily mean the o-ring is bad, but possibly the sealing surface of the outer caliper body or the adjuster shaft could be degraded such that the o-ring simply can't seal. The outer o-ring is pretty small and there isn't a lot of allowance for dimension deviation. We scrap a lot of outer half castings that are too far gone, even though they'd probably pass the pressure test.

As far as the inner adjuster not doing anything...keep in mind you're turning a gear, which in turn drives the adjuster. If you spin the gear clockwise, the adjuster shaft is spinning counterclockwise attempting to draw the piston back away from the rotor. Once you hit the limit of travel, everything will just spin. If the piston is sticking in the bore, it's possible the mechanism has pulled out of the piston...try running the inboard adjuster clockwise to run the piston out until it starts moving, then grab some channelocks or a clamp or something and without turning the inboard adjust, try and squeeze the piston in to re-seat it over the adjuster mechanism.

That being said....if the outer adjuster is leaking, the calipers will have to come apart for, at the very least, a cleaning....but it's likely the o-ring was rolled during installation or stuck at some point and was subsequently damaged upon a recent attempt to adjust the outer piston.

End of the day, those calipers should be rebuilt or exchanged for a set of quality rebuilt units...

@PatMc

Thanks for your response, i think you are correct about the o-ring seal not being seated and probably happened during adjustment, and also what i had done was turned it counter CW and drawn the piston out, but once i realized this , once the new pads were placed in i was able to get the venting set correctly and lock it into place, some pressure on the pedal and a short drive and right now no leaking, so it may be reseated, but will watch this closely. My only question is, can that o-ring be replaced with out removing and rebuilding the caliper?

Thanks .
Phil