If my master cylinder were to be leaking, where would I check?
 

Im having issues losing brake fluid, from my observations, I have ruled out leaking calipers. My next though is either the master cyl and/or the booster. Where are some problem areas I can look at?

around the o-rings where the plastic reservoir snapps into the master cylinder and underneath the master cylinder on the brake booster the paint will be peeling off

I assume you mean the level of the fluid drops in your master cylinder. If that IS the case, you will find evidence of that in the form of brake fluid at the site of the leak. So in general, take a flashlight and check ALL the hoses, hose fittings, the caliper pistons, bleeder screws and also look for fluid on the front of the brake booster below where the master cylinder is attached to it.

I have this same issue on an 85 right now. Does fluid go into the brake booster or is it stopped by some type of seal or O ring where the MC attaches to the booster? Looks like some fluid has leaked down the booster under the MC. I do not want to replace the MC only to find out the problem could be in the booster.

The amount of fluid leaking out is so small and so slow I really cant tell exactly where it is coming from.

Brake fluid should not go into the break booster. The break plunger should keep the fluid where it needs to be. Since these cars are 15+ years old, the plunger is probably worn out. It's very easy to replace or rebuild.

There is no passageway for fluid into the brake booster from the back of the master cylinder and there is no fluid in the brake booster. So the leak is the result of a faulty seal at the rear of the master cylinder. It will only get worse so best to replace/rebuild the master cylinder soon before it fails on you when you least expect it.

Thats what a friend said, that fluid is leaking past the seal on the MC and possibly into the booster

my master cylinder made a hissing noise every time i stepped on the brakes. u might wnana listen for it

It's not the booster. As mentioned during previous posts there is no fluid in the booster. The master cylinder is probably your problem. A plunger from the master cylinder actuates the booster. If the paint is peeling on the booster it's probably the master cyliner plunger. You can get a rebuilt master cylinder for less than $100 and it's an easy removal and install. Get the mastercylinder with the reservoir attached. That way you don't have to install the plastic reservoir onto the master cylinder. If you do have to install the reservoir onto the master cylinder, put a bit of brake fluid on the o-rings for lubrication. Install the o-rings into the master cylinder. Remove the reservoir cap and place a soild piece (like a block of wood) centered on the reservoir. Use a C-clamp and tighten down. That should solve your problem.

Man, I wish I would have thought to do that when I put a reman master cylinder in my car... would have made it alot easier! The rebuilt MC was like $44 at advance auto. Make sure you take care of the fluid leaks early because the brake fluid will mess up/ strip off your paint... mine was so bad I had to repaint the whole drivers side frame rail in the engine bay... it is also dissolving the undercoating under the car where it leaked down, I'm going to have to take care of that asap this summer.