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Old 02-04-2007, 06:13 AM
drdonpalmer drdonpalmer is offline
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Join Date: Nov 2006
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Default Re: H1 Hummer Rear Caliper Rebuild

Ok, First I want to say thanks to Harkness for all your help. I appreciate it.
I read through everything I could get my hands on and how to take the piston cap off still was not explained so I just decided I was going to destroy it so I could get the caliper built.
Now in-case your reading this at a how-to and I just lost you, keep reading because it has a happy ending.
I put the caliper in a vise and started laying into the edge of the piston cap with a small screw driver and a hammer until it peeled back enough to get a pair of needle nose vice grips on it, but that didn't work. Until I got two areas on the cap peeled back and with the vice grips attached I struck the vice grips with a hammer and the cap came right off. The cap is very maliable and I was able to easily correct the damage I cause to it and when I pressed it back into position after the rebuild, it looked as good as new...well, very close.
See Pics...well, I have pictures, but can't install them. I'll email the pictures to someone on here if they will post them.
Now as for the rebuild...I ran into some more snags. One is that the kit includes a dust boot and a piston seal, but DID NOT contain an o-ring for the piston retaining screw. Since it looks like that was part of the cause of my leak in addition to the piston seal, my caliper is still leaky, although a lot less, after the rebuild. I will be obtaining a new o-ring to correct the problem.
Another problem was getting the piston back onto the thrust screw and back into its bore. You have to follow the instructions and engage the parking brake lever because it puts pressure on the cone clutch on the back of the piston so that when you turn the piston it will actually thread on. Without that pressure, you will turn the piston, but the cone clutch will just stay stationary and your piston assembly will not advance into the bore. Now that's how its suppost to work, but I couldn't get mine in even with the above procedure. I'm sure I'd STILL be trying to get it into the bore if it weren't for the fact I had the piston compressor for the FRONT calipers. I have BOTH piston compressors, but the rear one won't work unless the piston is in about a quarter of the way and despite a very large C-clamp, it wasn't big enough for the very large rear caliper the H1 uses. So with the front compressor and a large washer, I was able to use the parking brake lever in combination with the piston compressor, while turning the piston with some very large channel locks, to get enough pressure to get the piston installed.
As with anything, now that I've done it, it is really a cinch.
I hope this helps someone in the future, because I could have used this thread.
Thanks again Harkness,
Dr. Palmer
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