The Stovebolt Site Forums The Shop Area Engine Shop Paint wheel cylinders?

I'm up grading to a dual master cylinder and new wheel cylinders and brakes.(funny how new wheel bearings got out of hand!) Is it acceptable to paint the wheel cylinders and if so what colors are used most often? I know brake fluid will wreck paint but I would really like to slow down the rusting that ruined the 44 year old originals!
Thanks for your help guys.

Johnny,

I am no expert in this area but my guess is that the old brake cylinders were ruined by internal rust (pitting), not external rust. If that is the case, the best way to extend the life of a brake cylinder is to flush/bleed the brake lines often (if you use regular fluid, which absorbs water) or use silicone fluid (that does not absorb water).

Do not consider using silicone fluid unless all your rubber parts are new (in the master cylinder and in the wheel cylinders).

I painted my master cylinder "cast gray" (it can be seen) but did not paint my wheel cylinders. On my suburban, I installed all new brake system parts, so I am now using silicone brake fluid in that system.

Good luck,
Tim

Not absorbing water is actually a problem with using silicone fluid on a street vehicle. Because water will not mix with silicone fluid, when any moisture gets in the system it will form a tiny droplet. That droplet can move through the system. When it gets to the cylinder area, your brakes only have to get to just over 200 degrees for that droplet to boil which will cause vapor lock and loss of braking until it cools.

Glycol based fluids will absorb small amounts of moisture and disperse it through the system. Because the moisture is dissolved, small amounts will have much smaller effects on the boiling point. Wet reflux boiling point is the brake fluid specification which gives a measure of how badly the fluid will be affected by moisture. Brake fluids which are labelled LMA or LWS usually have an additive which reacts with the water so there's almost no change in the corrosion or boiling points.

Harold , I am concerned about your post .
If the hydraulic system is a closed system , ie , no leaks , and synthetic fluid is being used , then where would water get into it.
My wifes old 180b Mercedes benz has had synthetic fluid in it for over 20 yrs , it sat for 6 yrs at one time , the brakes were still perfect after this .
The statement you make about vapour locking needs qualifying , I think .
Where did you get your data ?

Most of us are aware that regular hydraulic fluid is hygroscopic and needs changing every couple of years for best performance , despite the possibility of and H2O being "boiled off" .
In fact , it is a requirement on my bus to change the fluid every 2 yrs , for its certificate of fitness . Regardless of the mileage covered.

I wasn't planning to paint the inside of the wheel cylinders, just the outside! I saw first hand what happens to them when the fluid isn't changed. The rust comment I made was not made seriously. :rolleyes:
Since I'm replacing with all new wheel cylinders AND a new dual chamber master cylinder, would they be safe with the synthetic fluid?

In my opinion , absolutely .
I base this on the fact that synthetic fluid could not be sold in the USA if it was going to be dangerous when installed in a vehicle.

Back in the late 70's early 80's I worked for the company that made Castrol's DOT 4 LMA fluid.
Here's a couple references that I could find quickly:
http://www.hotrodheaven.com/tech/brakes/brakes8.htm
http://www.xs11.com/tips/maintenance/maint1.shtml
http://www.bestbrakes.com/brake_fluid.shtml

The silicone fluid boiling point is lower than the DOT 4, but if installed right, the silicone won't corrode the system. It won't mix at all with regular fluid. Racers don't use it, because of the boiling point. As for absorbing water, regular fluid, will do that still in the can. You will never notice it, until you use it in a race car system and see it boil, sooner than it should. Boiling means your brake pedal goes to the floor when you have been hard on the brakes, due to the air from fluid boiling, in case it is a strange term to you.

Johnny- Don't run the synthetic fluid unless you have replaced ALL the parts in the braking system. The synthetic and non should NEVER be mixed. There really is no reason to use synthetic. Dot 3 or 4 fluid will work just fine for almost any brake system. New cars don't even use synthetic. It'll cost more, and the info that I've seen shows that the boiling points are both lower than that of DOT 4. (big discussion in class about this one) Most people are not going to be boiling the brake fluid in their braking system. Unless you are hard on the brakes all the time, you won't run into this problem. I would just use DOT 4 and not worry about it. You can paint the wheel cylinders if you like, but it really won't make any difference. If the wheel cylinder leaks, then you'll replace it anyways. Plus, noone will be able to see the paint you put on them, and rust really won't matter. It would take a long time for it to rust through a wheel cylinder. Just some thoughts. BTW, I have a sheet with wet and dry boiling and viscosity of the various brake fluids if anybody wants the info. John.

As far as paint goes, I would use black. I have bought new cylinders that were painted that color. The calipers on my bike are black.

Thanks guys! The info on this site is always good.

Great thread folks.

-W