Stuck Wilwood Pistons
 

When I went to rebuild my calipers and blow the pistons out of the calipers a couple wouldn’t come out. Most come out but a few don’t budge.

I have a couple thoughts.
1) hit them with a heat gun to help liberate them and then hit them with air.
2) a solvent to break down crud and old seals.
3) insert a rubber stopper I can compress with a nut and bolt and then apply some torque to liberate them.
4) breakdown the calipers via side bolts and some combination of #1&3

Put the other pistons back in just a little bit and use a clamp to keep them there. Then use compressed air.

If these are track calipers then there is no dust shield and should be serviced regularly.
The dust shield keeps water and dirt out of the pistons.

Pat is right on, use a clamp on the good ones, holding the good ones in place and use air and WD 40.

You should be able to move the pistons back in and out a little several times to get the lub in there. The build up of dirt or corrosion should come loose. Unless that piston has not been working at all.

Then hit the outside of the pistons really well with a green Scotch Brite pad.

Calipers with square o-rings by chance? If so you will want to split the bodys and use a combination of compressed air and some kind of inside puller like your rubber stopper idea. Rock the piston while you put air pressure to it. What I tend to see with Wilwood calipers with square orings is if the caliper body gets deflection it shears the corner of the oring and it gets bound between the piston and the body causing the issue you are having. Don’t think heat is going to help.


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Yea, square rings.

In regards to the clamp, I feel like using a thicker wood block between the pistons that move and a thinner one where they’re not is equivalent?

Is using wd40 inside calipers body not a big deal? I’m probably going to get them powder coated again anyways so I guess hitting them with brake cleaner after using wd40 would be doable.

A wood block should work just fine as long as it is precisely the right thickness.

You are replacing the orings anyway, WD isn’t going to hurt anything else. Check the piston bores for burs before you put new ones in.

Using the thick/thin wood block like that should work. Watch your fingers, those things are going to come out at Mach 10.


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The problem with a wood block is that the opposing piston will come out. If it is a 4 piston then you can use the block for two but the one opposing the stuck one will pop out.