Hydraulic cylinder treatment?
 

Where you have a hydraulic slave cylinder with fluid on one side of the piston and air on the other, is there any coating or treatment for the exposed cylinder on the air side? Movement of the piston will keep the fluid side clean but air and residual fluid tends to rust the cylinder that doesn't see any piston travel, rubber bellows or not.

Is there a coating (lithium grease?) or something else you can use to protect this surface?

Where I'm experiencing a problem is the clutch slave. The inner portion is fine but rust & crap builds up just beyond that where there is no travel. As the clutch wears changing the throw, the piston now has to ride past the sludge/rust causing fluid leaks and ultimately failure. As fun as it is to remove and clean hydraulic cylinders, doing so as few times as possible would be nice.

I believe there is a paste/grease for when you rebuild wheel cylinders and they are going to sit on the shelf for years afterwards. Perhaps that would be your answer. But if you use anything that is not compatible with the brake fouid or your rubber cup, you are going to cause more problems.



I just did a google search and it looks like the product reuired is called redrubbergrease: http://www.redrubbergrease.com/

Re Rubber Grease
 

If you use rubber grease on a clutch slave, you might get away with it. The problem is heat. If brake cylinders are lubed with rubber grease around the pistons & especially the bucket rubbers, the heat of the brakes will harden it into a deposit on the cylinder wall that will cause leakage. i.e. The heat range of some rubber greases does not match the"DOT" rating of the brake fluid. The "shelf" lubricant for brake parts is silicone based. The "Red" grease seems to have heat resisting capability. I use the silicone.
Ken Thomas
C60

My "now sitting on the workshop bench" dis-assembled clutch slave cylinder (Bendix 76988) had a bunch of thick brown fluid on the 'air' side of the piston. No amount of regular bleeding/fluid replacement would get to that so off it came. My first look in the bore gave me sweats. But I see most of the 'rust' was congealed fluid that is coming off quite nicely. Heat may be a problem, but even the little bit of fluid finding itself past the seal is sitting on the bore and I may have to resign myself to that being a semi-annual maintenance item. The accelerator and clutch master cylinders have fluid on both sides of the pistons and that fluid is clean and can be replaced. little chance of rust here. I hope.