Vintage 911S Caliper Restoration Thread

[rick2]

Hey Eric, excellent post. Well presented and very descriptive. I have a question about the early casting of the M-Caliper. I wanted to make sure I am looking at the correct indention. I used your pic and circled the area that I am assuming that you are referring to. Could you please PM me with a price quote on a pair of S-Calipers with free moving pistons. Thanks for your help.
Rick

[Neunelfer]

Hi Rick,

A couple of things about M-Calipers:

I've circled the areas in red that I was talking about. Later M-Calipers also came with two humps around the bleeder area (I circled in blue). The later castings were made common for left and right. They would simply machine out the bleeder location as desired. The early ones had a slightly different bleeder notch. Even "later" M-Calipers came with the cup or dished out style of piston. These had more cooling surface. This also marked the end of the "knock-back" pin. We can talk more about those later.



This picture of a later M-Caliper kills two birds with one stone. This will show John the clear zinc finish and you can easily see the twin humps as we look down on the caliper:

[304065]

I nominate this thread for the best technical contribution of 2007.

[neilk]

Aren't there rubber seals between the caliper halves? If so, where did you get them? Nice job!

[Neunelfer]

I nominate this thread for the best technical contribution of 2007.

Wow... thanks!

Aren't there rubber seals between the caliper halves? If so, where did you get them? Nice job!

Thanks again, yes... there is a Porsche number. I think Roger gave it to me a while back. We don't use those though. They want $2.50 a piece (probably more now). They don't like to get them for you either. Most dealers can't find the number and the manuals all state that seperating caliper 1/2's is "verboten".

We simply sourced them to fluid and pressure requirements with a local o-ring/seal company.

I say yes, but, I should clarify. The M-Calipers use the seals (as you can see in the pictures of the spacers above). The L-Calipers do not as no fluid passes between them.

[John Straub]

This is great! Thanks,
John

[JohnT]

Did I miss the section where you sent the cast caliper bits out for a magnaflux (or what form of crack testing did you use?). These old calipers have frequently see too many heat cycles and can be extremely brittle. The classic failure is to spit out a chunk of metal near the top of the piston bore. Usually the crack starts inside the grove cut for the piston seal.

Things become extremely exciting when this happens on the track and only a little less so on a spirited drive. I've broken more than one front and learned all this from experience.

johnt

[Rich Lambert]

Neunelfer, do you have seals available for stock front & rear '66 911 calipers? It would be so much easier to clean them if they were split...plus, yours look so nice cad plated I might have to do that.

[Neunelfer]

Rich, we do have the caliper 1/2 seals. PM me your address and I'll mail some off to you.

Speaking of caliper 1/2 seals. We start the final segment here by bolting them together. The fasteners came back from the shop and have a new black finish.

We start by taking the nose 1/2 of the M-Caliper and lightly clamping it in the vise. Next we lay in the caliper 1/2 seals.


Then we lay on the spacers (Rich, you obviously won't have these with your 66 calipers) and lay the seals in their appropriate slots. I like to lubricate the seals with brake fluid.


Next we push one of the shorter outside fasteners up through the nose 1/2 and the spacers.


Then we simply drop the back 1/2 of the caliper down on the single fastener and line up the holes. The weight of the caliper 1/2 rocking against the side of the fastener will hold the fastener in place until you can screw the nut on.


Next we hand tighten the 13mm nuts on the fasteners. This will hold the calipers together and allow us to align the spacers before the final step...


...and the final step is torquing them down. There is a sequence and there is a required torque spec for these bolts. These are M8 with a higher hardness than the standard M8 hardware you see elsewhere on your car. If you look at the 13mm nuts you can number them left to right, 1-2-3-4. Torque as follows:

Set Wrench to 10 ft. lbs. Torque in the following order 2-3-1-4
Set Wrench to 25 ft. lbs. Torque in the following order 2-3-1-4

***M7 IS DIFFERENT***

For the rears:

Set Wrench to 7 ft. lbs. Torque in the following order 2-3-1-4
Set Wrench to 17 ft. lbs. Torque in the following order 2-3-1-4

Here's the M-Calipers getting torqued up. Note the proper Ribe R8 bit holding the head in place.


And finally, on the rear Wide L-Calipers we had to restore the lines. The lines come from the factory with a rust preventive coating. New lines are black. They also come with a rubber bump stop of sorts. You can do a couple things with the rubber stops. If they are in good shape, you can leave them on and replate your lines. The plating process does not harm the rubber. If they are cracked, you can cut them off with a knife and replate the lines. With Andrews lines, the rubber was cracked and brittle. We elected to cut them off and install new ones. Once the lines were plated, we masked off the ends and painted them with a semi-gloss black rust preventative paint (Zero-Rust). You can see the plated lines in the first picture we shot when they came back from the platers. The next picture (in a previous post) shows them painted. Then we cut new rubber to fit and split it up one side. We used the old piece as a template.


And here's the finished products!

M-Calipers:


Wide L-Calipers:

[Neunelfer]

Mark Schoeppner, you're "reply-to" email address keeps bouncing back.

(sorry for the bandwidth, I don't know how else to get in touch with Mark)

2-3 weeks is the answer