MDH

While attempting to replace the spring plates on my front calipers, the small allen-head screws that hold them in turned out to be every bit the trouble I knew they'd be. I heated them up and tried to torque them loose, but no luck. They were badly corroded, and immediately stripped. I tried the "chisel" technique someone suggested, but this essentially stripped the heads off without coming loose. At this point, I have the plates off, and the remainder of the screws still in the holes. I'm gonna have to drill them out.

What I need to do now, is gain access to the screws to drill them. The calipers appear to be two halves held together by four large allen head bolts. Has anyone ever tried to take these apart? A quick attempt with with an allen-bit/socket combination found they didn't want to budge.

It's amazing sometimes how one problem leads you into three or four others!

Michel

Red rooster

Wow, what a PIA!!! Dont split the caliper or you will be looking for a replacement.The seals etc between the two halves are NOT available.
Although it is too late now , what I have done is use a oxy gas torch ( with necessary piston heat shields ) to get those screws cherry red to break the thread lock that Brembo use.Then they just unscrew.
I dont know what to suggest other than have a look around and see if you can find a really good machine shop that has some better kit than you.
Maybe someone else has been here and found a solution .Good luck

Geoff

JasonAndreas

Unlike the Brembo calipers on the early 911s there are no seals between the two halves of a 964 caliper. The fluid connection between the two halves is through the metal connecting line. What I'm not sure about though is whether or not Porsche specified one-time use only stretch bolts? I don't remember the torque specification being that high or given in two stages. Any ideas?



photos courtesy of Gustav

MDH

Thanks for the input guys. I talked with a guy who does Porsche caliper rebuilds. He indicated the bolts usually don't come out - the most common approach is to grind/drill them out. Anyway, I'm sending them off to him for a complete rebuild. His prices don't seem that bad - plus he's gonna paint them for me while they're stripped down. He uses some kind of cured polymer process to coat them. I haven't run in to this before so I'm kinda curious to see the final results.

JasonAndreas

The bolts come out no problem as long as you use enough heat. There should be no reason to get a drill involved, the bolts are torqued with a high temperature adhesive!

If they are powder coating the calipers make sure they prebake the caliper before spraying on the coating. After the powder coating started to fail on my calipers I started looking at other Porsches and noticed similar problems (blistering, peeling, etc.) One of the major causes of this is moisture contamination.

chris walrod

These calipers can be taken apart just like already mentioned. I remove these allen head (sometimes they are torx) bolts very frequently before powder coating. I dont use heat, but do often times have to use a chisel on the sides of the bolt head, striking them in a CCW direction. They pop loose much easier than one would anticipate.

Jason brings up a great point about baking calipers prior to powder coating. It does burn off any moisture and aids in the initial adhesion of powder.

For this particular calipers, remove the four bolts that fasten the two halves together. Center punch the center of the broken bolt and drill carefully.

I would be more than happy to do this for you if you dont mind shipping the caliper to me. No sweat amigo

MDH

Chris - Appreciate the offer, but as I mentioned, I sent them out for a general rebuild already. I was willing to continue to try and tackle this, but I just couldn't get the large allen bolts that hold the caliper halves together to budge. I ended up putting an allen-head socket on them with a large (very large) cheater bar. Broke two 10mm allen head sockets and the bolts remained as they were. In fact, I put enough torque on them that I was starting to worry about breaking the caliper cores. My calipers were pretty corroded, and that probably complicates things. When I got the car several years ago, I remember even having frozen bleeder valves that I had to twist off and drill out.

Red rooster

I admire the confidence of guys splitting calipers without knowing bolt spec/torque values/locking compound spec.
I am all for having a go BUT my life depends on these things!!I think I will stick to my original comment.
Geoff

JasonAndreas

Gustav Frank posted the specs (i think everything but the DIN number) he received from Brembo? on smartgroups sometimes toward the beginning of the year but the search function is still broken over there and I don't remember them off the top of my head.

chris walrod

M12 bolts (into ally) should be 34ft./lbs., M14 54ft./lbs. These are not stretch bolts, or at least they are not made to be stretch bolts

JasonAndreas

Thanks Chris!

Red rooster

Are these bolts 8.8 or 10 strength.With 6-10 tons on 4 bolts they need to be good to not elongate and lead to leaks !Any tips on aluminum face distortion ?
I guess high temp lock compound must be used on brake calipers -anyone know which one ?
These arent idle questions but stuff that anyone splitting a cliper MUST know.
My 2.0c
Geoff

Bill Verburg

The caliper through bolts are 8.8