How many of us are there? Owners of Dodge based RV's?

Griff in Fairbanks wrote:
'Freeing' stuck or sticky master cylinder pistons:

Before proceeding, consider you're going to use a lot of time and brake fluid to do this. It may be cheaper and faster to replace the master cylinder.

This is temporary fix ... you'll be rebuilding or replacing it anyhow in the near future. Also, you won't know until after you're done if the seals are still reasonably good.

The objective is to use fresh brake fluid to dissolve the old gummy build up.

If the master cylinder piston is totally stuck (won't move at all), you may have a different problem, making all subsequent efforts futile. Likewise, you may wind up investing too much effort or not be able to dissolve the gummy buildup.

Step one is to remove all old brake fluid from the master cylinder and replace it with fresh fluid. It doesn't really matter how you do this. However, you want to make sure fresh fluid gets down where the piston is.

If you're the patient type, who allows things time to work, leave it overnight. (If the piston can move, even slightly, you can help the process by working the piston back and forth a few times every 4-6 hours.

You can try to hurry things up by immediately beginning to work the piston back and forth. But be careful. Being impatient always carries a risk of causing damage rather than fixing things.

If at some point you don't seem to be making an progress, you may need to dump the fluid you've been using and replace with fresh fluid.

Eventually -- hopefully -- you'll get the piston to move freely for the full length of it's travel.

Now, you get to find out if the seals are still any good. More than likely, you've destroyed the seals and need to rebuild the master cylinder.

The above is the exact process I've used to restore very old, very rare master cylinders. In one case, we had to machine new seals, using liquid nitrogen to freeze suitable rubber before and during machining.

I also know, from firsthand experience, that new and remanufactured master cylinders are available for extremely unique applications and vehicles dating back to the 1930's. (While I don't have firsthand knowledge, I believe this applies to vehicles from the 1920's and earlier.)