Brake piston pusher

[opelspyder]

I have rebuilt brake calipers now several times. The method of removing the pistons is a little scary to me in ways. They suggest using air pressure to blow the pistons out. Actually the instructions from ATE state to make a special plate to blow one out, then cap over the empty hole, and then blow the other out. They suggest using a piece of wood to prevent launching a piston. I have fought with some of the pistons before and have given up assuming they were rusted in, as air pressure would not allow them to budge. The problem is air compresses, where as fluid does not (or at least not measurable by us) I was at the parts store the other day and saw he had a machine to make all brake hoses, even stainless. And then it hit me. So I had a hose made to adapt to pipe thread. Then a bushing later I have adapted a pressure hose from a porto-power cylinder to my brake caliper. This is a lot better to control, and makes those stubborn pistons no problem to push out. This is messy though, put they do not blow out and make you leary either.
Here is the picture of the setup
Keith

[jordan]

This looks like a nice set up, I have used the grease gun method when air has failed though the grease is a mess to clean up and dissolve out of the caliper. I imagine the porta-power will need a fluid fill up quite often this way.

[Killer Texas GT]

Great Idea, Do you use brake fluid in the pump instead of Hydraulic Oil?
That way you would not have to worry about getting all of the Hydraulic Oil flushed out of the caliper with denatured alcohol with some other type of pressure pump.

[opelspyder]

I do use hydraulic fluid, as this still is used for my shop press. Once the pistons are out, most of the fluid comes out, a little brake cleaner, and it is flushed out. I usually clean them up afterwards, and even wash them with a soapy water, air blow the calipers out, and then paint, and reassemble. You will need to refill your pump, but stubborn pistons are a thing of the past. I think I have trown some away in past years just because air pressure and lube would not push the piston out. Even after working them in and out a little. This set I just did were like that, and turns out the pistons were in excellent shape, just stuck for all this time
Keith

[wrench459]

The pushing out of the piston is scary.
Now I pull them out much more safer.

[BQS4]

Keith;
One thing I have noticed over the years, is that granted there's some rust, or even "varnishing" in the piston bore to keep the piston from coming out, but, mostly I have found that it's a ridge at the opening of the bore that's made from crud, rust, road grime, brake dust, etc, similar to the ridge at the top of a worn cylinder in the motor itself. I have found that taking a sharp X-ACTO knife, and gently scrapping this ridge off generally allows the piston to pop free using the aforementioned air pressure, or even a couple of screw drivers in the piston groove will easily pop the piston out, for those who don't have an air compressor.

[blancojp]

I don't believe you guys have seen rust until you work on a late '30s car. In any event, we use a different method which works without any tools per say. We heat brake fluid to about 130 degrees and drop the caliper in. We then leave it over night and the next day, the pistons come out generally with just your fingers.

Remember the pistonis basically floating in place being held by the internal O-ring and the outer seal. Most of the problems come from deposits that form behind the front seal which tend to lock up the piston. The O-ring side is usualy OK so if you like Gene says, depending on how long it has been locked up, clean the area and it should slide out with slight effort.

[SpringGT]

I've never had any trouble getting the pistons out with compressed air, but as you said, they rarely ever come out at the same time.
I found that a good way to plug the open bore, while removing the other piston, is to use an expandable-rubber engine block freeze plug. It also helps keep the other piston from flying completely out, since it fills part of the caliper gap.
The proper freeze plug size for the opel caliper is 1 7/8"-2" (47-50 mm) and is available at Auto Zone, et al.
Bob

[opelspyder]

Well, I know there are a few tricks to do, but when you have to get it done and keep moving, I look for the quick way out. The pump seems to work for me
Keith