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914World.com _ 914World Garage _ Tale of the leaky caliper

Posted by: bandjoey Oct 27 2009, 08:32 PM

~~Have~~ Had a great rear caliper. Bought a set of 4 rebuilts a year ago and just now need to put them on. 3 are perfect. Went to adjust the outer vent clearance screw on the rear, and suddenly fluid started poring out of the screw.

?? Did I overtorque the screw - Strip it out of the Piston - Bust a seal - or what? What happened? I've not seen the inside of the caliper. Is there an Oring or seal under the venting screw? What keeps the fluid in?

Rebuild or replace?
Thanks for the info Bill

Posted by: SLITS Oct 27 2009, 08:58 PM

Are you speaking of the adjustor screw? They are sealed by an "O" ring as I remember.

Talk to Eric Shea .......

Posted by: bandjoey Oct 27 2009, 09:06 PM

yep. The outer adjusting screw. Can't find a pix anywhere, and the rebuild kit doesn't say where the really small seals go. I'd think an Oring seal but not sure

Fear is that the piston is stripped and hope it's just a seal.

Posted by: underthetire Oct 27 2009, 09:31 PM

Yup. O-ring. Hard to find the little bugger by itself in the right size.

Just order the kit from PMB. Lots easier.

Posted by: Eric_Shea Oct 27 2009, 09:57 PM

Uncle SLITS drove me here.

You're safe... looks like you blew a seal (to which you reply; "no, it's just ice cream").

PM me your address and I'll send you an o-ring and tell you how to install it.

Posted by: bandjoey Oct 27 2009, 11:47 PM

PM Sent. After this is finished, If you want the old cores, I know we can work a deal for price of shipping and YES! an Ice Cream Cone.

Posted by: Eric_Shea Oct 28 2009, 10:19 PM

A couple of seals left today... now:

You'll need to take the caliper off and remove the pads to do this.

1. Take either a couple dental picks or a couple small screwdrivers and "flick" that small c-clip off the outer adjuster shaft. Here's the method; use one "stationary" against one edge of the c-clip. Use the other to "flick" the other edge of the clip until it moves. Once it starts you should have an opening against the shaft that you can fit the pick or screwdriver into... cover it with your thumb and pry it off. OTHERWISE... the clip will go flying across the room.

2. Remove the 13mm nut.

3. Carefully remove the dust cover clip.

4. Turn the adjuster counter-clockwise with a 4mm hex to move the piston out. If it is not coming easily, tap the adjuster down to the surface of the caliper with a plastic mallet, then back it out counter-clockwise with the 4mm hex (rinse and repeat until the piston comes out). This method works on the most stubborn pistons and it helps preserve that frail 4mm hex adjuster.

5. Once the piston is out, set it aside and push the adjuster out.

6. Remove the defective seal with a angled dental pick if you have one.

7. Soak the new seal in a little brake fluid for lubrication and hook it with the angled dental pick. Loop the seal on the adjuster and walk it down the shaft as you would imagine a hula-hoop falling to your ankles. Do this until the seal fits into it's galley.

8. Lube that section of the shaft with a little more brake fluid and prepare to re-install.

9. Part of the preperation is making sure that bore the seal rests in is clean and free from burrs that might tear it.

10. Re-install the adjuster buy applying pressure and turning back and forth slightly until the adjuster is seated.

11. Re-install the 13mm lock nut and clip.

12. Pull in the piston while applying pressure to the piston face with your thumb (lots of pressure). Re-install the dust cover clip, pads and pins and re-mount the caliper.

Good luck.

Posted by: bandjoey Oct 29 2009, 09:26 PM

Thanks Man!
Thanks for the help and instructions. I found your classic thread on rear rebuilds too. Excellent writeup!

Some of your stuff is on my Christmas list...now if I can find a job in time, it'll be on the 2009 list instead of the 2010 list.

Bill