Mike,
Raybestos makes top quality NEW master cylinders.
Only buy new units, rebuild units never last long........:typing:
Here is why, rubber seal seldom fail in master cylinders and even wheel cylinders. Believe it or not the rubber lip seals are the most resilient part of a brake system.
Master cylinders and wheel cylinders usually fail from pitting of the cylinder bore. Rebuilt units are honed to remove these but many times small pits are left and or the bore is too over sized to maintain a good safe
seal to the lip seal. Also some remanufactures use the old pistons over which also can become pitted. These poor quality controls used to keep the prices down make for a dangerous part.
Many rebuilt masters don't work off the shelf. If they do work, your driving with a time bomb, your brakes could fail at anytime.
I bring this all up as a warning, my belief rebuilt master cylinder should be outlawed.
Just make sure you always buy new!
Mike

 

mevang, i have a ford escape (2002) that appears to have an extremely slow mc leak. maybe 6 months to a year to go from high to low. would you replace now or wait or what?

 

When you say leak, do you mean a lose of fluid, or do you have a drop in pedal say when sitting at a light? This is important as the first think you need to do is establish if the master cylinder is actually your problem.
Lose of fluid is not necessarily a bad master, unless you can see a trail of fluid from the back of it where it attaches to the brake booster. Then some units will actually leak into the booster where you can't see the leak.
Pedals that bleed or leak off with no signs of fluid leakage anywhere are a good indication of a internal by pass in the master. But you can be fooled here too.
Any time a master cylinder is suspect a full brake inspection should be done. Block off all brake hoses and test if the pedal is bleeding off.
Spongy or soft pedals are rarely a master cylinder fault and leaking ABS valve can mimic a master cylinder problem.
Modern brake masters seldom fail, but the master cylinder is still one of the most unnecessary replaced parts. Poor diagnosis is the cause. But if you are sure your master is leaking or bypassing I do suggest that your replace it right away. This part is the number one safety device on your car don't take a chance with it.
Mike

 

I agree with MEvang. Rebuilt units never last long. If you want to invest in Raybestos, get them new.