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-   -   stuck caliper pistons (http://forums.pelicanparts.com/porsche-911-technical-forum/708888-stuck-caliper-pistons.html)

Boydskyking 09-29-2012 08:25 AM

stuck caliper pistons
 
does anybody have an idea how to remove brake caliper pistons that are stuck, I have tried high pressure air , WD-40 etc. Your help would be great.

gsxrken 09-29-2012 08:52 AM

Can you reinstall them and use the brake system's own hydraulics? Put a block of wood to stop the other pistons coming out, stand on the brake pedal and you'll have 1100PSI trying to push it out!

kimlangley7 09-29-2012 08:58 AM

How much air / psi were you using? I've had "issues" with stuck caliper pistons - was only using about 60 psi pressure in the tank and not budging the pistons - cranke dthe tank up to 120 psi - and the piston popped out .

I would think though the max pressure available is to reconnect the calipe rto the brake line - let the hydraulics generate - as noted use a block of wood to "catch" / absorb the piston > and make sure all the other brake calipers are configured ok

86 911 Targa 09-29-2012 09:01 AM

Brakes
 
Quote:

Originally Posted by Boydskyking (Post 7004267)
does anybody have an idea how to remove brake caliper pistons that are stuck, I have tried high pressure air , WD-40 etc. Your help would be great.

Had the same issue, took them to a brake shop who told me they used 160 psi
to remove the pistons.

Try your local brake shop.

Good luck,

Gerry

tonythetarga 09-29-2012 09:15 AM

Heat + air pressure and some hammer tapping on the caliper. repeat and then repeat again until they pop out. Be careful to use a C clamp that will only allow the pistons to move but not all the way out. If one pops out you'll have to reinsert to get the other. It is best if you can ease them both out by getting them to move before you go the full way out in one shot. They rarely come out equally.

boyt911sc 09-29-2012 10:10 AM

This is the way to do it at home.........
 
Quote:

Originally Posted by gsxrken (Post 7004300)
Can you reinstall them and use the brake system's own hydraulics? Put a block of wood to stop the other pistons coming out, stand on the brake pedal and you'll have 1100PSI trying to push it out!


Boydskyking,

If your are rebuilding your brake caliper, you should have a good idea how the brake hydraulic system works. You need a lot of pressure for a stuck piston to slide out from the caliper. Compressed air work too but not on a severely frozen brake piston!!!! Hydraulic pressure is what you have available and use it. Slide the piston/s step by step using difference thickness of wood blocks. Don't let one of the pistons pop out during the removal. Synchronize the outside movement of the pistons.

Tony

Scott R 09-29-2012 10:12 AM

If you have a spanner you can try and rotate the pistons inside the bore a bit to unstick them. Then as suggested above use more PSI, and watch your fingers.

DaveA 09-29-2012 10:41 AM

I've removed stuck pistons from many calipers - using a grease gun. Unscrew the part from the gun that is used to fit on the grease nipple. Now screw the grease gun hose or tube into the caliper where the brake tubing fitting threads in. Attach a C clamp on both sides of the caliper to make the pistons come out evenly. Work the grease gun, and lossen the clamps on both side evenly, and soon your pistons will be out. This method will not harm the pistons. You'll also have grease to clean up!

jibmaster1 09-29-2012 11:00 AM

brakes
 
Quote:

Originally Posted by Boydskyking (Post 7004267)
does anybody have an idea how to remove brake caliper pistons that are stuck, I have tried high pressure air , WD-40 etc. Your help would be great.

First soak the piston area with PB blaster. Over night if it's really rusty. Do you have access to an air compressor? I have one for my framing tools I used. Go to your hardware store and buy a adapter that threads into the port that the brake line screws into. Put a towel over the area because likely one of the pistons will fly out now. Next, I cut a thick 1/8' rubber circle the diameter of the opening of the piston that just popped out. Place a large washer over that and get a big c-clamp and clamp the whole thing. Apply the air again. The other side should pop out now. Good luck. Now clean the insides well with 1500 grit steel wool and rebuild them using caliper grease. Good luck. Oh, there's guy that rebuilds 914/911 calipers on the forum and his stuff is TOP NOTCH! That is if you have a few Benjamins to invest in brakes. I think his shop is PMB Perfomance? Guy was super cool and helpful with me. Often comments on the site here too and gives good advice.

Fishcop 09-29-2012 04:41 PM

The guaranteed and safest way is to use a grease gun. Believe it or not, the threaded fittings of a grease gut are an exact match for the bleed nipple. Pump the gun and the pistons WILL gently and safely push out. There is grease to clean up afterwards, but a bit of kerosene and compressed air quickly sorts it.

http://forums.pelicanparts.com/uploa...1348962038.jpg

fanaudical 09-29-2012 04:59 PM

Another +1 for the grease gun trick. It's super effective!

ivangene 09-29-2012 06:31 PM

grease gun is what I used too - watch your fingers - when the piston "pops" out there is enough force to really hurt you

I will also say if you dont want grease in your caliper - just use the head of the grease gun and pour brake fluid into the opening - (upside down) that worked wonderful and took only a couple minutes

gjmascoli 03-16-2013 07:16 AM

I have four calipers from a '76 with severely stuck pistons. Took one A-caliper to a shop and he tried 150psi, no dice.

Is the grease trick more effective than air?

Or should I just re-install on the car and use the brake lines to force then pistons out?

chris68 03-16-2013 07:28 AM

stuck caliper piston
 
Another one for using the grease gun.

It applies much more pressure than you'll get from the air line. It's safer too, because the grease is less compressible and hence stores less energy under pressure than air.

Cheers

chrismorse 03-16-2013 08:20 AM

+1 grease gun
 
I too tried 120 psi air and it didn't even budge the pistons

It never occured to me that the threads might match up to my grease gun, so i put together this piece of brake line and a grease nipple.
One side popped right out, the stuck one required that the old piston be put back in to and clamped in place, to allow the pressure to push it out.

Look the old pistons over carefully, one of mine had a broken section of "ring", adjacent to the notch.

As others have said, Eric at PMB is the Man. Very helpfull and good parts, like stainless piston and caliper seals.

chris

http://forums.pelicanparts.com/uploa...1363447201.jpg

ivangene 03-16-2013 08:59 AM

grease gun is hydraulic pressure and WAY higher then air, and way less dangerous IMO...(which is why back hoes dont use air to move their buckets)

when the air "pops" out the part it could become a projectile (expansion of gas vs liquid)
in either case done put your fingers between parts while under pressure. blocks of wood or other are your friend

motogman 03-16-2013 07:55 PM

Brake system max operating pressures are 1500-2500 psi. Air compressors are ~ 150 psi. Not sure where a grease gun is but likely a bit above an air compressor. You can also push them in to break them loose if you have a way to apply a load. Easiest way is on vehicle.

James Brown 03-17-2013 01:18 PM

some hand held high pressure grease guns reach 10,000 psi, most around 500-2,500 psi. much safer than air pressure.

Reiver 03-17-2013 03:33 PM

grease gun and put a block of wood between the pistons to catch them.

Eric_Shea 03-17-2013 07:52 PM

Fluids don't compress...

Air will not work on calipers that have been sitting. In fact, it basically only works on calipers that are working.

Grease is the best way for the home mechanic. With any fluid you wont need wood blocks because the piston basically plops out. Most inexpensive grease guns have a 10x1 fitting under the nozzle. Remove the nozzle and screw it right into the caliper (saw a picture in the thread showing just that). The only problem is... the mess. Once you get the pistons out, seperate the 1/2's and blow air back down the fluid passages so the grease goes into the piston bores, then wipe from there (hold your hand over the bore because the grease will fly out and land all over... you) ;)

Clean up with brake cleaner and REPLATE. Rust never sleeps.


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