JDS968

Does anybody have a non-M030 left rear caliper (951 352 421 02) in usable condition [does not have to be pretty, just has to work] that might be for sale?

Thanks!

chudson

Hey JDS - not trying to hijack your thread but there is no M030 rear caliper. They are the same part number as standard suspension car.

alxdgr8

Probably not what you are looking for but I have a set, don't want to separate though. Freshly media-blasted, ready for powdercoat/paint/etc. $150 shipped.

JDS968

Excellent point, not sure why I wrote that.

What about pistons/seals, crossover pipes, springs, all that other stuff? Are they in working condition, or do they need further parts/assembly?

968gene

There are some differences in the type of piston seal and "PORSCHE" script when comparing early vs. late calipers starting with the 1986 951 through the 1995 968.
Racers seem to prefer the early style seals. The script issue is cosmetic only.
I have both styles sitting in my garage if you would like pictures.

odurandina

brake rebuild kits at Paragon for the win.

JDS968

Sure, I'd appreciate the photos.

Is there any issue with running calipers with the old type seal on the same car with other calipers using the new type seal?

Already rebuilt it, still doesn't function properly. At this point I just want to replace it with a caliper that I know works, and try to diagnose/fix it at my leisure.

968gene

Is the piston sticking or is the pad binding in the stainless bracket? Rust forms under the bracket and causes the bracket to warp and bind the pad. The brackets are also available as a rebuild part or you can grind a bit on the pad to make sure that it slides in the bracket (not the best solution).
Since the pistons are the same sizes, there should not be an issue with mixing old and new style calipers.

JDS968

The piston is "lazy", that is, it extends slowly under braking pressure but not evenly with the other pistons, and I cannot get it to apply full force to the pad, so the pad hits the rotor slightly unevenly.

968gene

I hope this is helpful. The First picture is of the 968 caliper (in this case its a 1994). Notice the stenciled PORSCHE logo and the large rubber seals around the pistons. The second picture is of an earlier caliper (in this case I believe it to be a 1986 951 caliper). You can see that the PORSCHE logo is part of the casting and has large block type. The font type may have been different for later calipers with the cast in logo. Lastly, you can see that the seals are not like the later style. I hope this helps.

JDS968

Thanks! Good to know, I've never seen them side by side before.

docmirror

This is piston to bore interference. It's common on older cars or where the fluid hasn't been changed often enough because some water gets into the fluid and causes the surface corrosion. It's not difficult to fix.

Disassemble the caliper, use compr air in the lines to pop the piston out if it's sticky. Once apart, take some 1500 grit wet sandpaper and some brake cleaner and clean up the bore in the caliper. You'll likely find most of the corrosion at the bottom/inside of the bore. Keep cleaning until it's really smooth.

If you have access to a lathe, reverse chuck(from inside) the piston in the lathe and use the 1500 and brake fluid to clean the piston. If you have some 2000 use that next. If no lathe avail, see if you have a sanding drum, or a grinder drum that will chuck in a drill. Use some elec tape to build up the drum so that the piston will fit snuggly on/over the drum with tape. Spin the drill and clean the piston with 1500 and brake fluid.

Get new seals and assemble with liberal brake fluid. It'll work fine again.

JDS968

I already rebuilt the caliper with new pistons, seals, and fluid. When I rebuilt it, both the old pistons and the bores were shiny and smooth with no visible corrosion, pitting, or scoring. This is consistent with the maintenance history of the car (yearly fluid changes for its entire life).

968gene

My vote is to still look at the pad retainers. Raj and others have described the binding that can take place between the stainless bracket and the pad created by corrosion behind the bracket. Good luck with your project.

docmirror

Heat warped. Sigh,,, carry on.