Rear Calipers Problem in Georgia!

AirJose · 06:32 PM

I have tried to rebuilt the rear caliper of my '69 three times. everything looks good until they are installed. Once I start bleeding, then they leak! upon opening I find the piston seals broken. What gives!!!can anyone help? I'm almost giving up. Thanks...Jose

AirJose · 07-24-2003, 07:41 PM

Any ideas?...opinions...? advise...?

craign · craign's Garage

Are you using a "power bleeder", I have not used one but I understand you can over pressure the system while bleeding and pop seals.

Other than that I am at a loss.

Craign

cgarr · cgarr's Garage

I rebuilt all 4 of mine without any problems, I used some caliper grease/lube and gave the piston a little twist to install, all done by hand, I did not compress it with a c-clamp until it was all lined up.

Craig

912UK · 912UK's Garage

Same here I used a porta pack to blow out the stuck pistons (kids make sure an Adult is present ) and cleaned them all out with very fine 1200 wet and dry new seals with some brake fluid and fitted it all in by hand. No probs it was only when I went to do the MOT test I thought oh I hope the brakes are fine ..well I got 75 % all round which is GREAT... so sorry unless you have really damaged pistons or you are forcing them in ????? can't help.

I did find also that you can get different size seals for years. Just because you car is say a 69 has it really got 69 calipers??

It has been about 30 + years of tinkers ..... people forget these things that's how engine blow up after re-build a mix and match of all years parts..

measure check it all out and let us know

Mark UK

Oh have you when you have cleaned they all up the calipers got the grove that the seal sits in 100% clean and there is not any muck sitting in there?? which would raise the height of the new seal....Sorry i type too fast (spelling )

AirJose · 07-26-2003, 08:28 PM

well, good advise. I cleaned the pistons, but not the groove; I remember that it was somewhat pitted inside the groove. I will open them again and clean the seal groove. I also forced the piston with a C clamp, and had no idea the angle of the piston is crucial. I placed the seal around the piston and it appeared to be the correct one. Will try again one last time. Thanks ! your insight was very helpful. Thanks to all !!!

Sweetheart912 · 07-27-2003, 04:35 PM

Hey from Augusta GA. I also have a 69...where is Rex relative to Augusta? I recently rebuilt all four of my M calipers and had no problems.... EXCEPT you have to have the right kit! Initially the vendor send me ATE rebuild kits that said for Porsche 912 65-69 & 356 C/SC. I found these kits were SMALLER in diameter in the O ring and dust seals, and that when I reinserted my pistons they bound and tore the new seal. Most vendors stock the wrong kit for the 69's. Notice the brake pads on the 69's are a bit bigger. Notice the shape of the rotor hats are different also-that's why the rear rotor for a 69 costs @ $200 more than the 68 & prior-OUCH. You need to order the 911 M cal kits for the T model. If Rex isnt so far away, maybe I can help out. Let me know. Oh, above all else CLEAN every bit of grime out of the seal ridges etc etc and use a good brake assy lube when putting things back together. Good luck.

AirJose · 07-28-2003, 07:52 AM

HI: I am about 2 hours away, near stockbridge. I think that you hit the target! maybe I have the wrong kit!!! It will be a pleasure to meet you and maybe you can help me to rebuild them. But first I will need to get the right ones. Let me know which are they and the part number if you have them. Do you live before Augusta near I-20? I met a nice retired gentleman w/ a green '69 912 that I gave him some porsche hubcaps but we lost contact. Well thanks in advance. and sorry I did not answer sooner... Take care, Jose.

Sweetheart912 · 07-28-2003, 10:46 AM

Jose, maybe we can link up some weekend. The Porsche part # I had was 901.352.998.00 for the kit. The Ate# is 13.0441.3805.2 Make sure by asking for the rebuild kits for a 911 69-73 Solid Rotor M Caliper (911 T's for sure, and I think E models too had the solid calipers).
BTW make sure your pistons are smooth an clean and the little "hats" on the back side move around freely and are not damaged. This is a crucial part for the out/in/centering of the pistons. If they are stuck, take out the circlip, remove the hat and clean well then reassembe with brake assy lube. Since you said you forced one - check the pin inside the caliper that the piston hat fits onto...make sure its not bent when you reassemble. When you get the right kits, take one of the damaged rings and hold it up to the correct one & you'll immediately see the size difference. When ready to go, lube up the O rings and the piston and center it with a little pressure by hand. Then gently start with the C clamp and it will start to go in smoothly until it hits the rings where you will get a tiny resistance as the intereferce fit starts, just keep steady pressure and continue it in until seated. If you have to really reef down or jam it-STOP...back it out, something is NOT happy and you have to figure what it is. Make sure your pistons are seated well back into the caliper - almost flush so that when you bolt them back up the pads slide right in. Clean all the hardware and use a little Neverseize on the ends of the pins that hold the pads in & a tiny dab in the ends of the "cross" the pins ride over. Use some neverseize on the bolts that hold the caliper on. Double check me, but I think the proper torques as 58 ft lbs for these bolts.
If you bought pads from the same vendor who sold you the kits, chances they are the wrong ones too. Check them out to make sure you have the right ones. The 69 912 pads are noticeably bigger. I used Mintex pads @ $25 for the 2 rear wheels and @$28 for the fronts. I masked off the interior of the caliper and plugged the holes and spray painted mine back to gold before installation for the final touch. I recommend you use ATE fluid DOT 4, but at least a DOT 4 fluid if not ATE.
It sounds like you have the plan & skill...if you get stuck, send me some mail & we'll try it to figure it out...if no go, then cruise on down some weekend & I try to give you a hand. Cheers and keep in touch. George

AirJose · 08:24 PM

George, Thanks a lot! I have been using the wrong caliper kits, part No.901-352-964-11 they also have a label that says for 356c and 912, 65 to 69. I took that for granted. I have just order the 901-352-998-00 kits. I also have the same pads (D31) for the front and rear, so I have to fix that too... George, thanks a lot; I was really giving up on this rebuilt. If you come by ATL let me know so I can show you the project. I am now stripping the seven layers of paint and primer, and going to bare metal for the body work. If I can be of any help please let me know. Thanks again, Jose.

912UK · 912UK's Garage

AirJose I have put a few pic's on my web site I was in the same boat as you the link is at the top of the page photo page have a look it will keep you going

Good luck Mate

Mark UK

www.classic912.co.uk