Sticky Brake Pistons

[jyl]

I'm trying to rebuild my rear calipers. Pistons are sticking and brakes won't release fully. Got my air compressor working but it won't budge the pistons. Maybe that's 'cuz it is a crappy little 100 psi deal. Should I (1) find a local Pelican w/ a more powerful compressor, or (2) pay a shop to pop out the pistons (and what $ would be fair)?

[Tervuren]

Does enough piston stick out for you to try to rotate it a 'lil?

[aigel]

Does it read 100psi? That should be enough. The piston is what area? 2-3 square inch? That means you have 200-30 pounds on that piston.

I have only rebuilt my SC's pistons once. They blew right out.

G

[Oh Haha]

What car are you working on?

Are you sure the pistons are SUPPOSED to come out that way? The rear calipers on my Mazda had set screws that were turned to adjust the pads.

[jyl]

This is the 911. The previous time I rebuilt these calipers, I had this compressor and don't recall having a problem. I'll try again. If no luck, I might be able to cut/mutilate off the seal and expose enough piston to grab.

I thought that, worst case, I connect the calipers to the hard line, with no rotor or pads, fill fluid and bleed the brakes, and use the pedal to press out the piston. Being careful not to push the pedal too far. Would that work? Sounds like a big pita and waste of fluid.

[Hugh R]

Buy a short brake line that fits, cut it and attach to an air fitting so it doesn't leak air. You can use a piece of air hose and some hose clamps.

[Neilk]

Get a C-clamp and clamp down the opposing piston, then have someone gently hit the brakes and the brake fluid should push out the stuck one. I did that once with a stubborn piston.

[Rusty Heap]

PB Blaster is your freind to get you out fo sticky stituations. through a little heat on the piston housing with a butatne torch to may help expand the housing a couple though too.

[Bill Douglas]

Originally Posted by Neilk

Get a C-clamp and clamp down the opposing piston, then have someone gently hit the brakes and the brake fluid should push out the stuck one. I did that once with a stubborn piston.

That's a good idea Neil.

[wdfifteen]

Originally Posted by jyl

This is the 911. The previous time I rebuilt these calipers, I had this compressor and don't recall having a problem. I'll try again. If no luck, I might be able to cut/mutilate off the seal and expose enough piston to grab.

I thought that, worst case, I connect the calipers to the hard line, with no rotor or pads, fill fluid and bleed the brakes, and use the pedal to press out the piston. Being careful not to push the pedal too far. Would that work? Sounds like a big pita and waste of fluid.

Take out the pads and use wooden construction shims between the piston and the rotor to limit how far the piston moves. I've done it many times.

[john70t]

Originally Posted by Rusty Heap

through a little heat on the piston housing with a butatne torch to may help expand the housing

Just a little because there are rubber parts in there.

Use caution around sealed liquids. Friend and I used torch on a stuck caliper, and watched as the flex hose expanded like a balloon.

[jyl]

No torch option, calipers are powder-coated.

[wdfifteen]

Originally Posted by wdfifteen

Take out the pads and use wooden construction shims between the piston and the rotor to limit how far the piston moves. I've done it many times.

Whoa, I shouldn't post when I'm half asleep.
Take out the pads and jamb shims in between the rotor and one piston. Put shims loosely on the other side. I give it about 1/8" inch of space. Pump the brake pedal until the piston comes out tight against the shims. Loosen the shims on the other side. Pump the pedal. Keep going until both pistons are about to fall out. They should be easy to remove the rest of the way.

[jyl]

Well, eff. Took a closer look. The pistons are rusted to the calipers under the rubber seals, which weren't, apparently, sealing. They are not budging at all. I have them soaking w/ some penetrating oil but I fear the worst. So, how much are used ATE calipers like this (1989 911 Carrera, rears) and what is a good source?

ATE® - Porsche 911 Series 1989 New Brake Caliper

Or should I just bite the bullet and buy new (which I'd do from Pelican of course). Aggravating thing is, I'd need to have them powder coated to match the fronts, so that's more money.

[aigel]

I would do a WTB on here. These should be available cheap as take-offs from people that upgrade to something bigger and better. Then you can still rebuild them.

Time to move to a dryer climate!

G

[jyl]

Good idea, I just posted on Parts forum.

[aigel]

You can also try a dismantler, but it may be reaching the point of diminishing returns compared to buying rebuilt. I have always shopped at Parts Heaven Partsheaven New, Used, Rebuilt Porsche Parts when I was local. Great place - they ship.

G

[jyl]

I used to go there, and to EASY Porsche. Wish there was a place like those, up here. I'll try there if no reply to my WTB post.

[Flieger]

PMB Performance. Can't go wrong with Eric.

[1-ev.com]

here is good video: