brake caliper rebuild

[Alan Goettel]

Its time for a rebuild on my 86 911 calipers. The dust boots are pretty baked out. How difficult of a job is the rebuild? Any tips or tricks would be greatly appreciated.

thanks,

Alan

[John Block]

Alan

I did the front caliper rebuild as one of the first jobs wrenching my 85 cab. It was an easy job IMO. Waynes 101 book was indespensible for the details. You need an air compressor to blow out the pistons (Waynes book covers this, start one side about 2/3 the way to removal, clamp to hold position, blow other piston all the way out, KEEP YOUR FINGERS OUT OF THE WAY). Clean off rust inside piston sleeves and piston (hopefully there isn't much). Prelube pistons. Put it all back together with new dust boots. Bleed brakes. You are done. I left out numerous details. Others may chime.

John

[IROC]

It's one of those jobs that, after you've done it once you'll wonder why anyone pays someone else to do it. It's very easy. Hardest part is getting the pistons out. I use compressed air myself.

Clean everything really well (I even use some fine-grit sandpaper or emery cloth to clean the sealing surfaces of the pistons prior to re-assembly) and you won't have any problems.

Very straightforward...

Mike

[mfbarnes]

I used my little cheapy electric compressor, about $40 at Walmart, put on one of the plastic fittings, and just held it onto the brake line connection opening. It hit 30 psi in a few seconds....and pop went the piston.

I guess my only other advice would be to keep things clean.

[Gordo2]

Not a bad job at all,

My tips:

-Getting the calipers off is the hardest part. The bolts holding them in place can be difficult to get at. I found a cheap set of Stanley bent box end wrenches at Wal Mart that was just the right angle to get at them.

-Look into sanblasting & painting the calipers prior to taking them off. Don't want any delay getting back on the road for something you are likely to want to do "while you are at it". I sprayed mine with cast aluminum finish after sandblasting. Two years later they look good as new.

Gordo

[autobonrun]

The only little trick is that the pistons need to go back in a certain way. There is an offset on the inside of the pistons (the part that presses against the pad) that should be turned at the appropriate angle. I cut a triangular piece of cardboard to set the angle. It is supposed to eliminate brake squeal.

Wayne's book has details and so does the Bentley manual.

[Jdub]

Use the Search button: tons of information at this site.

Orient the caliper puck as per Auto's advice above. I used a piece of tin as a guide. Factor in new brake lines as well unless you are CERTAIN the current set are under five years of age. Use plenty of penetrant on the hard line nuts, and use the proper flare wrenches: NO compromise here this is critical or you will be in a world of hurt with rounded off nuts.

I prefer to paint after all is done, and am careful to mask off nuts that do not need to be painted for an original look. Many caliper paints out there now that resist brake fluid so don't use any old paint.

Be meticulous about grit and dirt - absolutely clean surface to work on and with. I like butcher's paper, ripping new pieces for just about every new task.

Again, be sure to use the Search button or you will be asking the question "How do I get a hard feel on the brake pedal: it goes to the floor?" You MUST preload the caliper pucks so the new brake pad just barely fits in there. Any additional and you will have slop until the entire setup wears to fit and the caliper puck begins to move out again.

Finally, a bicycle tire pump and hoses of varying ID/OD will get the puck out. Do not remove one puck completely until you have both about fully out.

Best of luck.

John

[vash]

i wedged the handle part of my wire brush between the pistons. with the stirring stick you get from the paint shop as a shim, i got a super tight fit. that way, i could pump with the bike tire pump without having to mess with c-clamps and stuff. one piston pops out, but not all the way and then the other will follow shortly. then unwedge wood and grap the pistons. the rest is gravy.

[qcwang]

Great advice!! I will be doing this too soon. Sounds like a bike hand pump or electric tire pump will do the trick to get the pistons out. This is good since I do have these two items.

I was planning on converting to speed bleeders. Anyone with experience with them?

Edit: I forgot to ask. How long did it take you to rebuild all your calipers? Just planning for how much time to set aside for this project.

Thanks!!

[Jdub]

The longest part will be waiting for the paint to dry.

Figure one weekend, removing bits on a Friday evening. It will probably take less time but that should do. Be sure to start applying penetrant now.

John

[KobaltBlau]

Originally posted by Jdub
The longest part will be waiting for the paint to dry.

yeah man, that's like watching paint dry. ugh.

[JeremyD]

I am a big believer in speed bleeders - - And plan on rebuilding a set of rear 993 calipers for my Carrera this next week

[Alan Goettel]

Thanks Guys,

I put new brake lines on this spring so the fittings are no problem.

I have a compresser so getting the pistons out is no problem. I did the search and I good to go.

[oneblueyedog]

Don't get your fingers between the pistons when you blow them out with compressed air. Use the wood strip. They can fly out of their bores. I bruised my fingertip badly a few years back.

[autobonrun]

Originally posted by Jeremy964
I am a big believer in speed bleeders - - And plan on rebuilding a set of rear 993 calipers for my Carrera this next week

I bought a pump up fertilizer sprayer just for my brakes. I bought fittings that allow me to connect the hose to the overflow connector on the brake reservoir. With about 15' of tubing, I can sit next to the bleeder valve and pressure the brake fluid through the entire circuit on any wheel. I still firm them up the old fashioned way, but this is a quick way to change out the fluid by yourself.

Not only that, I used the same pump up system to pressure out my caliper pistons. With no fluid in the tank, it builds up enough pressure for this job also. It doesn't take much pressure and when the piston comes out, it can pop out fast.

As the others have said, make sure your fingers are way back. When you hear the piston pop free, it's too late to move them.

[JeremyD]

Thanks autobonrun...