911 caliper rebuild

beany · 10-16-2010, 04:11 PM

I have followed all the info regarding rebuilding the brake caliper on my 80 sc. I am pretty sure the pistons are not retreating into the cylinders properly. I did ok untill the part about getting thebrake pads to push the pistons back into their cyliners. I have tried everything to get them to move. I cannot get the brake pads out of the caliper. Yes, I have removed the pins and retaining spring. Any suggestions.

Zeke · 10-16-2010, 04:31 PM

Pics? I don't quite understand what phase you're in regarding the assembly. Usually we place the pistons in the caliper body and press them in with a big pair of Channel Locks with rags to protect all surfaces. There are other ways, but none work if the pistons are cocked in the bores.

Not being able to remove the pads? Don't understand that. They should fall out.

Oh Haha · 10-16-2010, 05:37 PM

Do you need to get the brake pads out so you can start the rebuild process?

Try removing the cap on the master cylinder(place some towels around in case brake fluid gets spilled) and then pushing the pads/pistons back into the caliper bores.

You can then use a screwdriver or other tool that will fit into the brake pad retaining pin holes. Use the tool as a fulcrum to bring the pads up out of the caliper.

beany · 10-17-2010, 08:45 AM

I was able to finally get the calipers off but had to put them back on and pump the brakes to get the cylinders out of the bores. Now what do I do to remove the cylinders from the bores to do the inspection process and start the rebuild with new rubber parts? thanks beany

Oh Haha · 10-17-2010, 08:57 AM

Do you have "101 Projects for your 911"? This book, written by our host, has the detailed info you need to complete the job.

Check out this tech article on caliper rebuilding. I would suggest you read up on the process before going further.Pelican Technical Article: 911 Caliper Rebuild
The calipers should be removed from the car to make rebuilding easier. You should replace your rubber brake lines at the same time, "while you are in there".

there's a whole debate on SS lines versus rubber but that's for another thread.

James Brown · James Brown's Garage

Being there dual piston, you have to remove one piston at a time by removing the caliper and draining the fluid out. clamping one piston in its bore, placing a 1x4" in the caliper, and using compressed air to push the piston out. Can be a little dangerous so watch what your doing. Consult the "101" bible for details.

moneymanager · 10-17-2010, 11:23 AM

+1. compressed air works fine. But keep your fingers out of the way; the pistons can come out in a hurry!

Jdub · 10-17-2010, 01:02 PM

It appears that you have cocked the pucks into their respective bores. Prior to sliding the pucks back in to their cylinders you should ensure you are putting each puck back into the cylinder they came out of. Additionally, each puck should be cleaned and lightly touched up with Scotchbrite pad or equiv to remove any hardened stuff and expose any nicks or cuts that will cause problems. They need to be surgical.

And of course each puck needs to go in with the proper angling (is it 15degrees?). You can use a bicycle pump to push the pucks back out. However, if you have cocked them in enough the caliper is now a doorstop. Scraping anything while removing the puck gurantees fluid leaks and nothing but problems down the line.

Best of luck.

Zeke · 10-18-2010, 07:07 AM

20 degrees, but you need to know the reference point.

G450X · G450X's Garage

I also had to re-mount the caliper to free a stuck piston. If I had read through the tech article first I would have tried that and saved myself an hour of time and some brake fluid!

My brakes didn't squeak, and appeared to have the correct 20 degree configuration when I removed them - so I "cheated" and made a cardboard template using my calipers as a go by before I removed the pistons.

I now have no squeaks, and good brakes. I had a roar up front that I figured out (by removing the caliper) was a stuck caliper - it sounded like a bad wheel bearing. The tedious part, like everyone says, is to get the piston in straight and over the new seal while maintaining that 20 degree angle.

James Brown · James Brown's Garage

You can buy a angle gage or you can make one with the plans that come with the caliper seals from ATE. Something everyone needs in there brake tool box. Along with the power bleeder, the correct flare nut wrenches, pad puller, brake cleaner, good brake fluid, small scribe, brake assembly lube, scotch brite, reference book, nitrate gloves. With other common hand tools and parts, brake rebuilds can be done in 2-3 hours, tops.

Flieger · Flieger's Garage

You do not need an angle gage. Courtesy of Eric Shea at PMB Performance: Notice the bottom notch in the piston is in the middle of the cutout.

RWebb · RWebb's Garage

Dang! So I wasted over 4 minutes making an angle gage, and NOW ya tell me!

Superman · 10-18-2010, 10:19 AM

I always make an angle gauge out of a piece of cardboard.

Compressed air is the traditional method of pushing the pistons out. And yeah, they often come out with a BANG. All things being equal, I now prefer to keep the calipers connected to the brake hydraulinc system, and use that. Much more forceful than air.

A small 'c-clamp' type vise grip works well to retract a piston and keep it in place while removing the other piston. The c-clamp thing can put the pressure at the center of the back of the cup-shaped piston, guarding against getting the piston cocked in the bore.