stuck caliper pistons

[James Brown]

just fill up all 4 calipers with grease and send to Eric, he will love you

[47silver]

i used grease, and the mess took hours to clean.. if that can work with brake fluid in the grease gun i would use that method the nex time.

[vancouver86/911]

When I did this I had one that I had to put back on the car and then used the car's hydraulic system to push out the stuck piston. It worked great.

[Eric_Shea]

Originally Posted by James Brown

just fill up all 4 calipers with grease and send to Eric, he will love you

We use water... that's the best

[Scott R]

I use Brawndo, it has electrolytes.

[Pillow]

Great tip on the grease gun. I have two calipers that have one of the pistons stuck and 120PSI air is not cutting it.

Trying this tonight!

[DanielDudley]

Originally Posted by vancouver86/911

When I did this I had one that I had to put back on the car and then used the car's hydraulic system to push out the stuck piston. It worked great.

No point in even taking them off the car until they are almost all the way out. Just leave them hooked up, and have at it. With a little blocking, you can get them all advanced way out.

[Pillow]

Grease Gun FTW!!!

Wow that was easy. Great tip thanks for posting it up.

The grease gun male hose will attach in the caliper Input line female port. Not the bleeder valve.

[chris_seven]

You may need to make a system that will allow you to block the piston that moves first as the other won't unstick if it moves out of the body and it is common to have pistons that are unevenly stuck.


Another way is to have the calipers thermally processed.

Many caliper re-conditioners heat the calipers in a controlled pyrolysis oven to prevent them from setting alight.

The temperature is just high enough to degrade the seals and turn them to ash.

The caliper is then dismantled blasted in a wheelabrator type shot blast machine and then re-plated.

We used to provide some test rig design input to a local company that refurbished calipers and they used this system and re-plated within 3-4 hours of blasting using Nickel Zinc.

The re-assembled calipers were tested for leaks with air bit I would agree that it is not 'best practice' for removing pistons.

A water/glycol fluid works well.

[chrismorse]

[QUOTE=chris_seven;8726417]You may need to make a system that will allow you to block the piston that moves first as the other won't unstick if it moves out of the body and it is common to have pistons that are unevenly stuck.


Here is a shot from my prior post showing a couple of pry bars and c clamps used to retain the first piston that freed up. This allowed the pressure to work on the second piston.

chris
http://forums.pelicanparts.com/uploads22/hydraulic+out+piston1363447201.jpg

[doublebuffle]

I elected not to try the grease gun trick because of the "clean up" required. Great method though.

I'm shocked that none has mentioned this already:

In all likelihood, if you were able to remove your pads, the pistons are not all that stuck. You must have moved the piston back to relieve pressure from the pad!

With a c-clamp, compress the piston slightly into the bore. This will 'free' the piston and then you can shoot it out with a tiny bit of air pressure. I used 90 PSI, but just make sure you have a piece of wood and a ton of rags to catch the thing. If it shoots across the garage it will be damaged (and you will have a new project).

If this does not work, reinstall on the car and use brake pressure to move it, (substitute one brake pad with something thinner).

[Joe Bob]

I use a wooden block where the disc goes...120 pdi usually works but I HAVE used the grease gun method in the past.

[kuba_kuba]

Grease gun method. Unbelievably easy and amazingly compatible threads...

[chrismorse]

Originally Posted by kuba_kuba

Grease gun method. Unbelievably easy and amazingly compatible threads...

I went to the trouble of making an adaptor,(see pic) and found I didn't need it.

Air is very compressible, not very controllable and kind of scary. It works great on giant GM single piston calipers, but with smaller two piston calipers, It is tricky to control getting the second piston out.

Water, as Eric says, is cheap, easily cleaned up and controllable, but I am not sure how to generate the necessary pressure - the garden hose is maybe 60 psi and it is a long way to shut it off :-)

If I had it to do again, I would have left them connected to the car's hydraulic system and retained the first piston to ease out, then put the pedal down to get the second out - piece of cake.
chris

[70basket]

+1 on the hydraulic system method worked great for me even with my master cylinder on its last leg. I had to use blocks and clamps because some pistons were more stuck than others and you need to make sure come out at time.

[porschetub]

Originally Posted by Reiver

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

The grease gun method surpasses anything,if you don't put a spacer in between the pistons you risk the piston cocking over and breaking the caliper casting @ the extreme end of the stroke...ask me how I know that,yep and it cost me.

[porschetub]

Originally Posted by 47silver

i used grease, and the mess took hours to clean.. if that can work with brake fluid in the grease gun i would use that method the nex time.

Hours to clean up the grease???,brake fluid in a grease gun???
Best to read up on this,cheers.

[Pillow]

For those claiming to use water as the hydraulic fluid... How did you do it?

I used a 1/2-3/4" plywood as the block between the pistons and it works great.

Agree that a single piston is great for air, multi-piston calipers I will keep with the grease trick from now on. I do not like the violent ejection of the pistons with air.

[CCM911]

I just hooked mine back up and two pumps of the pedal had it right out. I am sure the grese way is incredibly effective as well, but I am far too lazy to then go in and clean out all the grease.

[Bergo]

I recently redid my 911S aluminum calipers, couldn't get one of the pistons out, disassembled the caliper and uses my shop press to get the last piston out.