My right front caliper is not working correctly. Would you install rebuilt calipers, or try installing the seal kits (left and right) to try to solve the problem?

 

I'd get a rebuild kit(s) from one of the big 3. I think they're about $15. Piece of cake to install. Should take you a couple hours to remove, clean, re-seal, install, bleed. I would do both fronts at the same time.

 

You weren't very specific - "...not working correctly" doesn't tell us a lot. The problem may well not be in the caliper at all. It is possible that the problem is a bad brake line. If you are going to rebuild the calipers, I would suggest replacing the flex lines as well.

 

Wally -

The local Porsche dealer diagnosed the problem as a caliper problem. This problem occured (pulling to the right) after they installed new front pads (Mintex purchased from you). The brakes worked perfect before pad installation, no pull. The car has stainless steel brake lines. I can't understand why they worked so well before installation of the new pads.

 

Sounds like the pads are in wrong or they only changed one side? Poor bleed on that side? Right side pads not bedded or scorched. Rotor warped. Bearing loose. Try swapping pads left to right in the front. Re-bleed. Go do some medium hard stops. Let them cool. Do it again. Or... take it back to them and tell them it pulls to the right, fix it please.

 

Mike -

They have swapped sides, etc... I have been told this problem can occur sometimes as the pads push the pistons out further and can hang up. It doesn't seem to make sense to me as they worked perfectly before the new pads. Very frustrating.

 

Get rebuilts from the big three and install them yourself. You already got screwed by this guy once, why go willingly into the night again?

 

Thanks for the advice all. New seals going in when received from 928 Intl.

 

Perhaps a brief explanation of disk brake caliper operation would help - or not ...

The caliper has one or more bores, with a piston in each bore. The pistons are a sliding fit in the bores. Cut into each piston is a square cross-section groove. In each groove is a square cross-section rubber ring. There is a light rubber dust seal at the bore opening.

When the brakes are applied, hydraulic pressure pushes the pistons out, distorting the rubber rings. The rings slide ONLY if the movement is greater than can be accomodated by the distortion of the rings. When the pressure is released, the torsion of the rubber rings pulls the pistons back just enough to release the pressure on the brake pads.

If the rotors are true, and the wheel bearings are correctly adjusted with no free play, it takes very little retraction movement to allow the rotors to rotate freely, yet keep the pads in light contact with the rotor. In this case, the next time that the brakes are applied, the distortion of the rubber rings will be sufficient to apply the brakes, and the rings will slide in the caliper bore only the microscopic amount necessary to accomodate pad wear.

In other words, if the brakes are right, the caliper seals slide thru the bores only twice during the life of the pads - once in during installation, and once out as the pads wear.

The pistons do move back and forth a tiny amount as the brakes are applied - but the seals usually don't.

If the rotors are warped or the bearings are loose, you will get "pad knock-back", and the seals will be pushed back in a small amount as the pads are knocked back by the rotor, and the seals will then be pushed out that same small amount by hydraulic pressure as the brakes are applied.

If a piston siezes in the caliper bore, a light brake application will not move the piston, and the other pistons in the caliper (if there are any) will have to move twice as much. If a hard brake application moves the piston out enough to apply the brakes, it will not move back when the pressure is released, and the opposing pistons (if there are any) will have to move further back to release the brakes. If the caliper has pistons on both sides, you might not even realize that there is a siezed piston until one pad wears out and the other shows little wear.

If there is only one piston in a sliding caliper, there will be no brake application if moderate brake pressure is applied. Therefore, a siezed piston on the left caliper will cause a pull to the right. The '83 floating frame caliper uses one piston, so it is possible that could be your problem.

One reason for sticking pistons is that the piston has moved out in the bore as the pad wears. When new pads are installed, the piston must be pushed back into the bore. If the brake fluid has not been changed regularly, there may be corrosion in the bore or on the piston. If a C-clamp (G-cramp in the UK) or similar powerful tool is used, the piston will be pushed into the corroded bore very firmly.

It can be difficult to get the stuck piston out of the bore for rebuilding ...

And let's not forget that the caliper frame containing the pads must slide slightly as the brakes are applied, and again as they are released. If the floating frame isn't free to slide, the effect will be much the same as for a siezed piston.