911 brake caliper rebuild, pistons not going back in

[VOLLGAS]

Rebuilding the brake calipers on my 1986 911: All 4 calipers are taken apart and cleaned fine. Calipers and Pistons are all good and re-usable.
Got new seal rings and dust boots from Porsche dealer.

Here’s my problem: All instructions say one should be able to just push the cleaned piston back into the caliper but mine are not going in at all!! Lacking the special Brake grease silicone, I’m only using brake fluid to lube the new seal ring and piston and am wondering if using the suggested silicone brake piston grease would make the difference here???
Online threads say to watch for not cocking the piston when setting it back in which of course I try but after 2 hrs of not a single piston wanting to go in at all I’m wondering if there is a trick or if it is really the missing silicone grease that is making this job impossible to do without??? Any tips are greatly appreciated!!!

Ralph

[Marty Kocse]

Rebuilding the brake calipers on my 1986 911: All 4 calipers are taken apart and cleaned fine. Calipers and Pistons are all good and re-usable.
Got new seal rings and dust boots from Porsche dealer.

Here’s my problem: All instructions say one should be able to just push the cleaned piston back into the caliper but mine are not going in at all!! Lacking the special Brake grease silicone, I’m only using brake fluid to lube the new seal ring and piston and am wondering if using the suggested silicone brake piston grease would make the difference here???
Online threads say to watch for not cocking the piston when setting it back in which of course I try but after 2 hrs of not a single piston wanting to go in at all I’m wondering if there is a trick or if it is really the missing silicone grease that is making this job impossible to do without??? Any tips are greatly appreciated!!!

Ralph

If you have the right seals in place, you should be able to push them in if you try real hard - you shouldn't hurt anything. It does take some grunt I must say, but they should go in. On my 996, the pistons are different sizes. Are you sure you have the right seals?
Marty

[VOLLGAS]

Thanks Marty, yes I double checked part numbers on the seals and everything. They are the correct, original Porsche, ATE manufactured seals. I got the proper silicone grease today, tried again and got all pistons in. As you say, it still took some grunt but they're in now. It felt that with the silicone grease the chance of getting them in crocked was much smaller but maybe I just had a bad day yesterday...

[ccm911]

You will want to use Sil-Glide from your local NAPA dealer. I am going to be rebuilding my fronts in a few weeks as well. A lot of bang for the buck. I hate to ask, but you DID have the bleed nipple loosened, correct?