If you get one out and the other is stuck, you can pop out the rubber dust cover from the cylinder you removed and place the piston back in. Hold that piston down (easier with an assistant) and shoot compressed air again. It should pop out.
I inserted Brian Carlton's procedure on removing a piston that is still stuck after using compressed air.
Quote:
Originally Posted by Brian Carlton
Firstly, if you're going to get into the fine art of rebuilding a caliper, odds are that one of the pistons is frozen quite solid in the bore. You're not getting it out with 100 psi.
Furthermore, when you apply 100 psi, the opposite piston immediately and promptly eject itself from the bore, leaving you with a stuck piston and an open hydraulic system.
The thing to do is to ascertain your condition prior to disengaging the free piston. Apply about 30 psi.........if one piston moves and the other does not............STOP.
Get a C-clamp and clamp the free piston so that it won't move.
Install the caliper back on the vehicle and connect the brake hose.
Press on the pedal and apply full hydraulic pressure to the stuck piston. This will amount to over 500 psi and the piston will eject itself.
Now, you've got the issue of an open bore and one engaged piston.
You'll need a sheet of rubber and a wooden block that covers the bore. Clamp the block against the rubber.........over the bore.
Now, use your air pressure...........40 psi will do it........to free the remaining piston.
DO NOT separate the caliper halves........
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Photo showing a split caliper.
Quote:
Originally Posted by tangofox007
According to MB, splitting the calipers is never in order. At least not at the field level.
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Use a pick and pry the old O-Ring out of the cylinder.
I originally scrub clean the calipers and pistons with mineral spirits and stiff plastic brush. Some would argue not to use petroleum based solvents in the braking system if not flushed out properly. So using acetone would be a safer choice.
Inspect the piston for damage or abnormalities. If the piston surface is corroded, use an emery cloth to remove the corrosion. If deeply pitted, then a replacement piston maybe needed. Also check on the cylinder bores for corrosion or damage or abnormalities. If corrosion or damage is bad then a new caliper body may be needed. I then finish cleaning the assembly with spraying acetone based brake cleaner to degrease the insides the cylinders, passages and pistons, and the outer caliper body.
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