Rear Calipers

[japomero]

Any reason that I cannot (should not) use water to push the pistons out of the rear calipers on a '71 FHC?
Thanks
Jim

[abowie]

Not as long as you clean and dry them straight away. Probably cleaner than the grease gun method.

[PeterCrespin]

Any reason that I cannot (should not) use water to push the pistons out of the rear calipers on a '71 FHC?

If you are pressurizing the water from a closed container pressurized by air, I'd just use the air if pos. In all forms of pressure displacement except grease, be careful to wrap the cylinder in heavy rag as the piston can fly out fast. The later brakes being integral are less hazardous but mind your fingers.

[abowie]

What Peter is saying is that if you try to use something compressible like a gas, and it releases suddenly, you have what engineers call an explosion. Or a bomb. Or a projectile weapon.

If you are able to use something non-compressible, like grease or brake fluid or water, then the risk or injury, death etc is far less.

This is why when pressure vessels are tested (eg SCUBA cylinders) water is used to provide the pressure, not a gas.

[MarkRado]

I usually try air and rags first and move over to the grease gun when pistons dont move immediately. The grease gun connects directly to the bleed screw by the way, plug the other thread with another nipple.

[japomero]

Thanks for the comments. Yes, I was planning to use water in a hydraulic tester to provide the pressure. Thought about air driven water but that just sounds like a way to make way too much mess.
Jim

[abowie]

That would work well.

One trick is to put a piece of 1/2" thick timber between the pistons. This makes sure they come out evenly and prevents one side coming out completely with the other side then stuck.

[mgcjag]

All sounds far too complex a quick puff from an airline usually pops them out