Caliper Rebuild/ Sourcing pistons

[chococrazy]

Hey guys one final step till she's officially driveable. 1989 Anniversary Edition 911. Both the front two calipers are stuck and after removing the pistons they seem spitted beyond repair. I was looking into reman calipers but after purchasing some I got a call saying that they don't have them . It seems impossible to find the front driver side, and our host doesn't seem to sell the proper piston.
Also- I'm having a hard time getting the second piston out of the front left caliper. I've tried shop air tomorrow I'm going to try a grease gun, but I was wondering if I use the grease gun do I load it with grease? Or use it dry? Will liquid wrench or Kroil help?

Thanks for the help in advance.

[Brando]

I would highly recommend contacting one of the members here, Eric Shea. He does caliper rebuilds/sales and does a damn fine job...

[G450X]

It's a bit of a pain, but I had to re-mount my calipers and use hydraulic pressure to force the pistons out. I used a small piece of wood inside the caliper to cushion the release of the pistons. I was lucky and had no piston pitting (high miles are actually good here).

Like most things, the first one is a bit rough, but the other ones get easier....

[djbrand1]

Yes, just keep the calipers on the car, remove the pads, put in a piece of wood or some rags, and pump the brake till you hear them drop. You'll lose some fluid, but much easier and safer than using compressed air to "pop" them out like little rockets.

After the pistons fall out, use a piece of wood to hold the brake pedal down about 1/4 to 1/3 of the way to prevent more fluid from being spilled.

[mepstein]

Eric at pmbperformance. he'll make them new again at very reasonable $

[Bob Kontak]

Are these the pistons you need?

Zim's Autotechnik Brake Caliper Piston, Front, A Caliper, 911 75-89

[Eric_Shea]

Thanks for the props guys.

The others have eluded to the fact that you'll need fluid. I actually find it easier to do on the bench vs. the remount on the car thing. You'll have much more control over which piston is doing what.

A cheap Harbor Freight grease gun will have a tip that is removable. What you'll have left is a 10x1 fitting that will screw into your calipers fluid inlet. Now all you'll have to do is control the removal of the pistons. We use a water pump but the method is similar.

I use a piston clamp to retain the outboard piston and allow the fluid to blow out the inboard piston. With A-Calipers it really doesn't matter which one. The piston clamp is fairly flat so it won't get in the way of the piston you're extracting. You can use a c-clamp as well, just keep it on an edge. The idea here is to simply hold that piston in place while the other one comes out.

Next, for A-Calipers, we use a large rubber stopper (and the piston clamp again) to seal the empty bore. A steel scab plate and a pair of c-clamps will work as well.

Pistons are "usually" very good. Do yourself a favor and use some 0000 steel wool on them. What looks bad is probably what I call "brake shellac" which is a combination of old fluid etc. It should come right off with very little elbow grease. We vibratory polish everything and paint the tops with a heat paint in factory grey. If they are pitted (which again is very rare for steel calipers) then the SS pistons are readily available.

What will usually be VERY difficult for A-Calipers are the fasteners. These are large M9 fasteners "but" they have a rather small Ribe R6 bit head. In contrast; the M-Caliper has an M8 fastener with a large R8 bit head. Here's the trick with the fasteners.

1. Use a Ribe Bit (not Torx)
2. Use a 1/2 breaker and a 14mm deep well on the nuts. (not an impact wrench... you need to feel this, you can easily snap the R6 bit)
3. Use the Ribe to "secure" the fastener only... DO NOT attempt to turn with the small Ribe bit.
4. Use heat and a penetrating oil if need be.
5. Go slow. I mean "days" if you have to. Some of these fasteners have taken weeks for use to safely remove. Why? They are basically NLA. Do a search for M9 fasteners, you'll see what I mean.

Finally, after everything is apart do yourself, your calipers and your car a favor and have them re-zinc plated. Zinc is what ATE used for the finish on these. Zinc is a sacrificial coating and will help protect the metal much better than poser paint.

Do not hone the bores after they've been plated... they will be factory new after that.

Have the fasteners re-plated in black zinc.

Re-assembly is pretty straight forward. Use assembly lube. The pistons usually press in by hand. Make sure you know the 20 degree angle trick (lower notch in the centerline of the pad cavity). Torque to 29ftlbs.

Here's a link to a Ferrari 365 GTC set we finished yesterday. Very similar to the A-Caliper... just a tad larger.

https://www.facebook.com/media/set/?set=a.10150286176513193.332173.72240238192&l=673282fc65&type=1

[chococrazy]

Thanks guys I'll look into Zim, but I think I'm going to get a set of spare calipers as this isn't the first time it happened.
I'll look into Eric's services too.