Brake Caliper Spring? Caliper Rebuild Process

[benzor]

So on the advice of a couple members, I'm rebuilding my calipers to see if I can renew my braking performance. See link below for original post:
Poor Braking Performance?

Did the Front Left yesterday, took a while to sand off rust on the sliding surfaces, but got the caliper back together successfully.

Here's my question: Should the spring clip that holds the two caliper halves together for the 944's floating caliper be flush to the cylindrical piece (that holds the piston)? Mine is bent, so that only the tip (in the middle of the spring clip) is contacting, which seems to create a lot of friction on the slide rails.

Bruce
944 N/A

[djnolan]

here is a diagram. Are you referring to #6 if a front caliper or #9 if the rear caliper?

[John_AZ]

Bruce,

Good picture above.
Here is a step by step DIY supplied by member ExitWound:
(Safe to open)

http://www.theexitwound.com/944/brakecaliper.doc

GL
John

[djnolan]

Very nice writeup. They don't look like porsche brakes however.

[benzor]

It's #6, the front left clip. John_AZ, thanks for the article, that's actually the one I followed. Sadly it doesn't have the same spring design, so it doesn't quite answer the question.

[fmartenies]

Bruce,

I am assuming you were talking about the piston (Part 12) and the inside surface of the cylinder (part 7) when you said you sanded rust of the sliding surfaces. Maybe the Porsche brakes are different, but that is almost always a BAD idea. The roughest you should get with those surfaces is steel wool and brake cleaner.

Even small imperfections on the piston will tear away at seal #13 that sits in the caliper. That seal has to form an air tight/water tight seal while allowing the piston to move in and out. Any break down and you will start to lose fluid which leaks onto your pads until they rot away. This is especially critical just below the scum line of dirt and corrosion that forms when dust jacket #11 fails as that is the area that contacts the seal the most.

Did you order a rebuild kit? Or are you just cleaning up what is there? Personally, I always try to clean and reuse first, and if I find the brake doesn't hold a seal then I start ordering parts. Curdled brake fluid and dust are usually the culprit well before seal failure. A good way to test without reinstalling is to get an cheap working motorcycle hand brake/master cylinder, mount it on a stand, and bleed your brake right on the bench. It will be easier to see if you are getting a good seal.

[benzor]

fmartenies - not to worry, sanding the bore is a bad idea. I was talking about the metal slides between the two caliper halves (not a controlled surfaced).

[mug23]

I have a question. What do you use to plugged the brake line while you have the calipers out for rebuild so that the fluids don't drip all over?

If mine lines are stainless, what do you guys use to plug the hole?

[benzor]

I plugged mine with paper towels, which was probably not the best solution.

[mug23]

How long did the paper towel last before it starts to drip all over? I just don't want the reservoir to be all dry up since it would be a big pain in the butt to bleed, correct?

[benzor]

It lasted the whole job, probably 4-5 days. The reservoir won't bleed dry - the gravity feed is not that strong, and there is some other fluids effect at work (which I clearly can't explain).

[OK-944]

I currently have the rear calipers off of my 85.5, and find that the bleeder screw caps fit quite nicely over the brake lines to prevent drips.