Should I be removing the pistons from the brake calipers for cleaning as part of regular maintenance? If so, any tips on how to get the piston out? I can't seem to get mine out with hand strength, and I don't want to mar it by using a tool.
What Mel said. No point unless the o-ring is leaking. When that happens most folks use very low air pressure to blow the piston out of the caliper. Use too much and it can tilt in the bore, catch the edge of the o-ring flange, and bend it or strip it off the piston.
What Mel said. No point unless the o-ring is leaking. When that happens most folks use very low air pressure to blow the piston out of the caliper. Use too much and it can tilt in the bore, catch the edge of the o-ring flange, and bend it or strip it off the piston.
Ok thanks. The reason I ask is that when I removed the brakes to get the wheels off, the right one started leaking like crazy. The piston had sort of pulled out a bit and the o-ring had gotten caught and pulled away from the piston. I took the piston out of that one... the o-ring appears undamaged and popped right back into place. It got me wondering whether I should pull the other one out.
If the o-ring that had gotten pulled/rolled away appears un-damaged, do you think it's ok to use?
O rings are cheap, but if I didn't have a spare and a close inspection showed no damage I'd re-use it. After re-installation hold brake pressure and look for leaks.
The reason this happened to you is that you wore the pads down past their nomimal minimum thickness (see your other post).
Next time, push the brake assembly against the disk (push hard but keep it square) so you compress the piston before removing the pads. You'll need to compress the piston anyway to get the new (thicker) pads over the disk.
Is it possible that your pistons are in backwards?
At one time it was discovered that there were a number of pistons that had been installed backwards. Make sure that the "longer" portion of the piston is outboard of the bore. i.e. The "O"ring should be an the inboard half of the piston.
With the piston in backwards, it is possible for the "O"ring to pop out of the bore with little wear on the pads.
And if you ever need to remove the piston, usually you remove the caliper from the plane, and tap it, sometimes a good whack, onto your bench and the puck will come out. You can also use a bit of compressed air. It does not take much air pressure. Be sure the puck is not pointed at anything if you use air as it will become a projectile. just set it on the bench, cover with a paper towel, with the puck pointed down and put a little air to it is the best method.
And of course on the plane, a little brake push will pop it out.
No - the pistons are actually stamped one one side with "This side out", to prevent that.
Something I've always been puzzled by about the brake design - there is no spring to open the brake pads themselves. The piston will retract by hydraulic pressure, and I have return springs on the master cylinders at the pedals to help ensure this happens. So the piston retracts, but the brake pads are then just sort of floating there, free to chatter and rub against the rotor (which I can hear when pulling the plane around by the tow-bar) even when the brakes are "off". Why aren't these designed with some kind of return springs on the caliper to open the pads themselves?
Thanks again. Another question... having removed the calipers for cleaning, do I need to completely re-bleed the brake system again (pumping fluid from the bottom up)? Or can I just reconnect the (now empty) calipers, open the drain plugs at the bottom, and pump the pedals to force fluid down into them again (perhaps topping up the reservoir if required)?
Thanks again. Another question... having removed the calipers for cleaning, do I need to completely re-bleed the brake system again (pumping fluid from the bottom up)? Or can I just reconnect the (now empty) calipers, open the drain plugs at the bottom, and pump the pedals to force fluid down into them again (perhaps topping up the reservoir if required)?
just set it on the bench, cover with a paper towel, with the puck pointed down and put a little air to it is the best method. 
