Rear brake problem
 

Ok here's the story from the beginning. My sons 72 was out of brake fluid in the rear chamber of the master cylinder,I found the left rear wheel cylinder was leaking.I replaced it with a brand new wheel cylinder,new shoes,bled brakes etc. Then we were servicing it later(don't remember how long due to it being off the road for 11/2 years for paint & rebuild) & it was dry again.Same routine as before,new wheel cylinder,shoes etc.This time I was being extra careful to make sure that I did not snag or some how tear the rubber on the wheel cylinder. Well as you are I'm sure guessing by now it's dry again! What in the heck can be the cause of this?

Re: Rear brake problem
 

I'm assuming you have power brakes on this one. If you don't, is it possible that it's leaking into the carpet or somewhere inside the firewall?

If you don't see a leak then the only guess is that there's still some empty air space in the lines somewhere. Brake fluid can boil from brakes that get overheated due to some malfuntion, but as far as evaporating into thin air, I don't think that would be the case.

At this point, I would make absolutely sure that all of the air is out of the brake lines and monitor it carfully for leaks.

Re: Rear brake problem
 

My bet is its leaking into the booster. It can't evaporate so it has to be a visable leak outside or into the booster.

Re: Rear brake problem
 

Yes it's got power brakes.I guess I forgot to add that yes I can see that it's leaking,I just can"t understand why the left rear only seems to be lasting about a couple months.

Re: Rear brake problem
 

Are the shoes out of adjustment? If they are way out, then this can cause the pistons to basicly over extend.
Also if there is a lot of rust in the system it'll cause them to go bad, but not in that quick amount of time though.