Rear Caliper Rebuild?, How to? Options

[hitbyastick]

Hey guys and gals,
sorry for the long absence. I was busy getting my 914 on a boat from Germany to Cali (ETA April 9th) and turning 21.
Anyway, the parking brake doesn't work. Seems to be kinda common. It engages, but doesn't release. Does a rebuild of the calipers help this problem? I know Porsche doesn't recommend splitting the caliper halves so I'm trying to stay away from that.

Thanks a lot,
Christoph

[lylegd]

It could be the caliper that is sticking but before you tear into the calipers, do a few simple tests to make sure that is the cause of the problem. If you pull on the parking brake lever and then release the lever, does the brake lever properly return to its home position? (If no, look to see if there is a lot of rust around the pivot shaft on the lever. Does it just need a few drops of oil? Also check to see if the return spring which is mounted in the left rear corner of your floor pan is still working properly. Many are broken, stretched or just fell off. The spring is covered up by a small metal plate held in place by two screws.
Disconnect the parking brake cables at the calipers and make sure the cables freely slide inside their housings. Also this test allows you to determine if both calipers have the problem or just one. Do this test by pulling the clevis pin out which is located in back where the parking brake cables joins up to the lever on the back of each rear caliper. While you have this pin removed, you have effectively isolated each of the rear calipers from the lever and cables so check to see if the E brake is still on. Check both sides. Even if it is still on, you still have one more test to do. If the brake is still dragging at this point, check to see if it is the inside or the outside or both brake pads that are applying pressure to the brake rotor. Do this test by tapping out the brake retaining pins, removing the separating spring that is under the pins and then pull the pads out one at a time to see which action frees up the rotor. Sometimes there is so much dirt and rust inside the cavity that the brake pads sit in that the pads cannot move freely enough to retract when they should. Also check to see if the brake venting gap adjustment is properly set at 0.008 inches. If it is set too tight, it will act just as if the E brake was on all the time.
Lastly, if your testing has determined that both of the all rearbrake pads inside both rear calipers are applying pressure to the rotor, then you may have residual brake fluid pressure all the time. You can quickly test for residual pressure by briefly opening one of the bleeder valves on either rear caliper. This will immediately but temporarily eliminate any pressure whcih might be there. Does this make the problem go away? This can be caused by one of several problems. 1) a binding brake pedal cluster bushing which isn't allowing the pedal to return all the way. This could be due to bad bushings inside the cluster. 2) Very old rubber brake hoses which are swollen shut on the inside of the hose. 3) Improper adjustment of the rod length that goes from your brake pedal to the master cylinder(Too long). After pressing on the brakes, reach down to the pedal cluster and pull up on the brake pedal. Did it move when you pulled on it? It shouldn't if all is well. 4) A worn out master cylinder that is preventing the piston from returning to its home position.

PS This website has some great technical notes on how to rebuild the calipers. It isn't an easy job but it can be done. You need to be a pretty good shade tree mechanic to do it. Lyle

Bottom line is that you need to determine if the cause is internal or external to the caliper. Then do these suggested tests to further isolate the cause. When did the problem start, have you or anyone else done any work on the brakes recently? If you don't feel comfortable with doing these tests, perhaps you can find some one else who lives nearby that may have experience with 914 brakes. This website is one way to find someone close by who shares your same hobby interests and might be willing to help you out. Lyle