How do I free up stuck caliper pistons on my 1975 164E?

BTW. So long as the chrome surface on the piston is okay and the quad ring groove is okay it won't matter if the bore has rust pocks. It is in effect a displacement cylinder with the quad ring acting as a gland seal.

I would go the grease way. The heat will destroy the seal between the housings. I learnt years ago that splitting the housings generally leads to a leak that is very hard to fix due to warping of mating surfaces.

If the air falls short and the oven has a cake in it...



Messy but it works.
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Art Benstein near Baltimore

A dog teaches a boy fidelity, perseverance, and to turn around three times before lying down.
-Robert Benchley

hi arty b- wow i have that exact small grease gun. have used it for over 40 years.very useful to snap on a needle point greaser extension. good for greasing hard to get at items like working parts of volvo hinges. always use tubes of molybdenum disulfide black grease. seems to have more staying power. btw surprised as hell that you can generate enough pressure with that gun to oust stuck pistons. keep up the good work. see you at the cafe one night on tobacco road. thanks tons oldduke

Ditto on Chris Mullet's response. The piece of wood between the pistons is very critical because if you crank the pressure up to 100 - 140 psi and they move, they will come out with a bang. There is a good chance that one piston will pop first and if you don't have the wood to restrain it/ slow it down, you have the opportunity for disaster. Once one piston pops, you will have to push it back in and restrain it with the piece of wood using some clamps so that you can pop the opposite piston.

There was no problem getting the front calier pistons to pop out on my 140. It was a no-go for both of my Girling back calipers. On one caliper I was able to get one piston out. On the other caliper both pistons were firmly stuck in place even applying air at 140 psi. For some reason the rears seem to be much more problematic than the fronts and rebuilds (at least for the Girlings) seem to be in short supply. I was able to source one from Rock Auto and the other from Iroll motors.

Hi,

If all else fails and you wish to go a little further to save the caliper, this will work.

Heat up the entire caliper by any means available. I use a large propane torch, also known as a weed burner, tiger torch or rosebud, depending on who you talk with. Heat slowly without localized heat, as if you're baking it. In a pinch a Bar-B-Q or even a campfire will work as well. You could use your oven, but I guarantee your wife wont like it.It helps to have a pair of sturdy tongs.

At about 400 degrees F a yellow flame will come out from the brake line holes and last about a minute. That was the O ring burning. When there is no more flame or smoke coming off the caliper, it's done.

Set it aside to cool, and the pistons will either slide out with gravity or you can pull them out with your fingers. As a bonus, most of the rust will have disbonded from the surface, and the bleeders will be free.

Good luck,
Peter

Sometimes you can blow them out with compressed air blown into the brake line port with the bleeders shut. A thin piece of wood sandwiched between the inboard and outboard pistons (piston boots removed) will prevent damage from the pistons slamming into each other. If one side's piston starts advancing more than the other side, you can hold it in place with a C-clamp until the stuck one advances.

This method didn't work for me as they had been sitting too many years and my compressor is only capable of 100 psi on a good day. I had to McIver a tool that grips the inside of the piston and then extracts it. It only works on the front calipers though.

If it's really hard to remove the pistons, then they are probably toast anyway so extracting them through any available means is OK as long as it doesn't damage the caliper bores.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)