I had two front cylinders that I could not get apart. I tried compressed air and it did not move at all. So I drilled and tapped for an 8 32 screw and put the screw in the vise and it took several very hard hits with a large hammer and a block of wood to remove the cylinder. After I honed out the cylinder and cleaned up the piston I installed new seals and it works great. Others may have tried this but I thought I would let everyone know that it works well (so far). Cheaper than buying new cylinders although more time consuming. It snowed all day today so I had the time.
They come out very easily if you attach the screwed end of the grease gun to the hydraulic port - most guns are 3/8" UNF - same as the hydraulic connection. Few pumps of the handle and out they pop......
I did try that first but it would not do it, even with the hammer it took several minutes of hitting it to come out. The greese method has worked for me in the past but not on these.
Oh well! It's never failed me yet - grease gun can develop 10,000psi! I've shifted some WELL stuck cylinders - and disc brake pistons with it. make sure you refit the little 'cap' that locates the adjuster - how did you secure that back to the piston?
the top caps on each piston fell off when I removed the shoes. I did not know that they were attached (until I got to the other side). I dont see how they could move once the shoes and drums are on but what do you think? any suggestions on how to connect them to the pistons??
I would strongly advise against using compressed air to free brake cylinder or caliper pistons for two reasons: it doesn't usually work very well; and if it does work, there's a chance you'll release quite a lot of energy in the form of the piston flying across the garage.
As Roy says, a grease gun is much more effective, and much safer.
Yes - you read about using air quite a bit - yet at 100 psi I think it's unlikely to 'unstick' anything very much. And of course the stored energy is impressive if suddenly released! Same reason pressure vessels are (initially) tested with non-compressible water - virtually no stored energy to be released if the vessel lets go!
