QuestionHow can I free up wheel cylinders that have been sitting for 50 years. Of course I would like to do it without damaging any of the parts. Cylinders are cast iron. Pistons appear to be aluminum. When I removed the cylinder a small amount of still-liquid brake fluid drained out.
AnswerHi, Eric!
You don't mention what type of car, so Ill keep my answer general.
This may not be possible to do without damaging the parts. The alloy pistons will have corroded and the cylinders are probably rusted from water in the fluid; brake fluid does absorb and hold a lot of water in this long a time.
Here's how I do this: I remove the rubber cups and the show retainers and any other clips and hardware, until the piston backs are exposed. Sounds like you've done this already.
Next step is to secure the cylinder in a bench vise with soft jaws. Orient the cylinder vertically and use a thick drift or piece or rebar or steel rod at least 1/2" in diameter, and a 2-pound ball pein hammer. A few good whacks will often be the only thing needed. On the other hand, you may end up cracking or distorting the pistons before they finally shift.
If this fails to work, you'll have to do the machine shop thing. They will try to press the pistons out, and failing this, will bore them out.
Next, if the wheel cylinders are badly pitted from rust, they can often be bored oversize and sleeved, or bored oversize and new oversize pistons fitted. This can change the brakes' feel, requiring more pedal pressure, though.
Pistons can be turned out of aluminum stock to fit the rebored cylinder.
This is pretty standard automotive machine shop stuff. If you can;t get it done locally, check with Hemmings online, under "Services Offered" for vendors who offer this service.
--Paul
