Re: Dragging brakes

[Carl DeSousa <desousa@cisco.com>]

> From: zm@mhcnet.att.com (Zafer Mehmood  [209])

> No, the master cylinder has never been replaced. But it doesn't leak and
> the brakes don't drag all the time. I think that when the temperature
> rises, the brake fluid is expanding and is not flowing back into the
> reservoir as it should. One experiment I am planning to do is to
> take apart one of the brakes, and push the caliper piston in (as one
> would do to install new pads) and see if the piston goes in easily and
> the fluid level rises in the reservoir. If it doesn't, then something in
> the ABS unit or in the master cylinder is preventing the backflow which
> could be causing the brake dragging problem. Is this a reasonable assumption?

Not if the problem is intermitent.  You would want to do this when the
problem actually occured.  Instead, next time it happens, run out to
the master cylinder and loosen the bleed screw of the front 
reservoir.  Observe for fluid to "squirt" out.  If it does, than the 
problem is probably in the master cylinder.   

> 
> The other thing I might do is replace the brake fluid again. The day I
> changed the fluid was very humid; it was raining and the relative humidity
> was probably close to 100%. I noticed that the paper towel I was using to
> wipe the fluid off, was feeling wet (as in wet with water) after some time.
> It seemed like the fluid was absorbing quite a bit of the moisture. Since it
> took me a while to bleed all 4 brakes plus the clutch, the fluid may have
> picked up a lot of moisture which could be causing the problem. Brake fluid
> is known to be hygroscopic and I guess I picked a bad day to change it.

I'm not sure that the brake fluid could have absorbed that much water
but I see your point, let me know if it works.

Carl DeSousa