help master cylinder

hi my 1991 chevy is leaking just when the car is just sitting and off when you under the car looking up its buy the master cylinder or the booster any idea to test them someone told to i have to change them both thank you

the best idea is to find the leak and see where its coming from. and whatever you find that is leaking, that is where the leak is from. Then you can either fix the leak or have it repaired. or u can use vasoline or something

Have fun cause you will be banned in a couple hours!

my s-10 was leaking out the master cly. and all it was was the rubber boot in the master cly. that was not sealed. makes sure it is sealed on the cap and make sure the cap is snapped on all the way around.

Iam pretty sure it is the seals. Buy an overhaul kit for it.