I recently completed alot of needed basic work on my 85 and one of the tasks was to rebuild my calipers. While at it I changed rear rotors and pads and installed DOT SS lines and replaced a few hard lines and had the calipers powder coated.
OK..I put it all together and proceeded to bleed the system with the new Motive pressure bleeder I picked up. I ran 2 liters of DOT 3 to flush everything out nicely and then ran a 3rd litre of the ATE DOT 4. I read a post that reccomended tapping the calipers with a rubber mallet to dislodge any air bubbles which I did and sure enough when I did that a few bubbles did pop out and thought, hey cool, good tip! I ran so much fluid to flush everything out that I had the chance to pump the pedal a few times on every corner. I did not depress the pedal anywhere near approaching past the 1/2 way point at any time. I read the posts about the seals yada yada. Great...done. I start the car and pump the pedal a few times about 1/2 way and they did firm up. I pull out of the garage and crap, the pedal is soft. I pump once and twice and pedal is firm and the car stops like a champ. I drive away and the next time I applied the brakes (15 seconds) SOFT. This keeps going on. Absolutely no leaks anywhere and there wasn't an air bubble in sight for the entire second half of my bleeding (with slight pedal pumping remember which is the best way to do it) which we're talking 1 1/2 litres without a bubble in sight tapping and all. I read the posts and picked up that the pistons may not have stretched their legs and stay recessed in the bore a bit too much when just rebuilt and have a longer travel distance to contact the pads. OK. I remove the new pads and slip in the old ones and apply the brakes which now drives the pistons farther out of the bore and gets them past the fine line. To get the new pads in I pushed back the pistons just enough so I can slip the new pads in again buttoned it all up pumped the pedal, felt firm in the garage with the engine off. I start her up pulled out of the garage and ....SOFT! Crapola! Exact same symptoms again. Stops like a champ after one additional pump again, drive a few seconds, soft, pump, champ. I bleed one more litre and not one air bubble..surprise!!!
OK...I then read a few posts that said it can take a couple of hundred miles (one to two hundred) for everything to seat properly before the brakes are 100%. Don't know why that would be but hey, you guy's have the Porsche experience so who am I to argue. So I drive and drive and drive. Clock 250 miles non highway (OK a little highway) miles and same thing goes on. I'm ready to put a sledge to the calipers at this point. Then a thought entered my tortured mind. Could it be that? OK. Whats wrong with the picture guy's?
OOOOhhhhhhh! Looks nice doesn't it? What's he talking about, what's wrong here?
Since everything was looking so pretty I decided to clean up all the hardware, springs and pins holding the pads in, on a wire wheel and then had the brain storm to paint them that lovely silver color. Red/Siver OOOHHH how nice. When I took out the new pads to put the old pads back to push the pistons out farther I noticed that the painted pins were kinda sorta binding on the pad retaining holes they're pushed through and the bottom of the pads (closer to the hub) were slightly closer to the rotor than the top where the pins are. Didn't pay much mind to it and went on with my tasks as I described above.
Now I take out the retaining hardware and wire brush the paint bye bye. I then put a slight coating of caliper grease on the pins and the surface of the springs where the pins rest on.
Put it all back together take the car out and hit the brakes.....SOLID!! Stops like a champ. Drive a little further hit the brakes....Like a champ!! Been good ever since. Now I can't be positive it was the damn paint or if maybe I just needed to drive 250.5 miles to seat everything properly I guess I'll never know for sure but I thought I had to share this with you guy's just in case anyone else might have a brain fart and decide to paint their retaining hardware because it looks soooo nice! DON'T!!!!!


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I'm so confused; I just ordered a master cylinder rebuild kit for the same problem.

 

LaughaC, Are you sure its the M/C ? Did you just do brake work on the car? What year is it? Did you do a few of the things I posted above to see if it rectifies the problem? I'd hate to see you do the M/C and still have a problem. What are the symptoms you have?

 

I always leave the pistons tight enough that I need a plastic hammer to fit the pads in. afaik the piston seals have a tendency to push the pistons out when new pads are installed loose.

 

I wish I new that. Everything I read on threads said to push them in all the way, even 102 projects and this forums tech section. Wasn't the problem as it turns out although I'm only 99% sure it was the paint.

 

afaik. either tap the pads in tight or maybe spend a couple of hundred mi waiting for the pistons seals to set up correctly.

also afaik when you excercise the pistons you push the pistons way inside.

maybe you won't have problems installing pads loose? I've never had that luck.

 

I'm going to have to do the front pads and rotors next year and will remember what I've learned here. Once you know....it's cake!

 

This might be a dumb question but it looks like you powder coated AFTER you bolted the halves together. Doesn't the powder coating process involve cooking the parts after the the electro static powder is applied. Wouldn't that also cook the seals? I've never rebuilt calipers before either so go easy on me.

jeff

 

Jeff, I did not split the calipers, this is a no no unless they are leaking at the halves. Nasty little O-rings in there that are a PITA to get and so are the special bolts I forget the technical name for them. The basic rebuild consists of piston seals and dust boots only. Yes the units are bead blasted and then heated but the heat does not approach the levels the calipers experience under hard driving/braking conditions so the powder coating process does nothing to the O-ring seals. It's pretty easy to rebuild your calipers, I was surprised just don't paint the pins and springs like someone I know did, just grease them lightly.

Gordon

 

Good to know. Thanks.