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Wheel Cylinder Fluid leak on BJ8

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67BJ8

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I replaced both of my rear wheel cylinders with Moss units about 2 years ago. I am using silicone brake fluid. The brakes were working fine when I stored the car for this past winter. I just started it up and I find that I have no brakes. I also have no brake fluid in the reservoir. I pulled the right rear wheel and found brake fluid all over the tire. I have some questions. Are the Moss brake cylinders usually very reliable? Could the silicone fluid have harmed the seal? Can the unit be rebuilt or should I just get another new one?
 
Check to make sure it was leaking from the cylinder as it could be leaking from the brake line or the bleed screw. I would think the Moss cylinders are good but you will know more when you pull it apart to see what failed. Since Silicone fluid does not absorb water, water that does get into the brake system will go to the lowest point. This can cause corrosion in the cylinder (that's why it's a good idea to flush silicone brake fluid on a regular basis). You can get the cylinders re-sleeved for about the cost of a new one. The re-sleeved master and wheel cylinders should last a very long time.

Cheers,
John
 
I agree with John. Inspection of the inside surfaces of the cylinder should give some clues. Look for corrosion, pitting, etc. Original cylinders were hard anodized aluminum on the inner surfaces. If the thin hard surface were removed by honing during a rebuild, corrosion would occur in a relatively short time. I don't know if Moss uses new original type cylinders or just has them rebuilt. It is always recommended to replace aluminum cylinders rather than hone them. As John says, silicone fluid would make moisture problems worse. A fluid such as Castrol LMA is often suggested. Sleeving the cylinders would eliminate the soft aluminum problem.
D
 
I took the cylinder apart last night. the inside looked fine
and was not pitted. The area around the bleed screw and the brake line connector were dry. Should I clean everything up
and try puttting it back together? I couldn't find a definitive cause for the leak. Or, should I just get a new one and not fool with it?
 
Are you sure it was brake fluid that was leaking? Any chance that it is leaking at the rear axle oil seal? If that is the case, then you could be loosing your brake fluid into the brake servo.

Another thought ... did you happen to remove the rear wheel and pump the brakes at any time? This could extend the brake cylinder to the point where fluid could leak out.

And finally a really crazy thought ... Did you go out to the garage and pump the brakes during any 40 below weather? Just thinking that if you had frozen water in the cylinder and compressed it, perhaps it caused a leak.

Cheers,
John
 
67BJ8, Sounds like all you need is a kit and reassemble the clyn and reinstall it. Do not just put it back on.Also consider using standard Dot 4 Brake fluid.--FWIW---Keoke
 
I believe there is some caution with mixing standard and silicone fluids. These guys will set you straight if you decide to switch.
 
Now that you have the silicone in there, it is ok. Just don't change back to regular Castrol LMA. Then you will really have leaks. Been there, done that.
 
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