hey how can i tell if my master cylinder is bad or my brake lines are bad. i checked all the brake lines behind the wheels and no leaks. my brake pedal is really spongey and goes almost to the floor. also when i filled up the master cylinder with fluid, it drained out in about a month. thanks

 

anyone wanna gimme some advice or anything before i buy another MC? lol

 

BLEED the brake lines

 

Unbolt the MC from the booster and see if any fluid comes out.
It could be leaking from the seal in there and collecting in the booster.

 

ok so i saw this thing on a thread i found searching. i did #2 of the functional test and passed. i also did #1 and #2 of the leak test and also passed. i dont know if this information helps but ya.

im gonna check for fluid in between the mc and the booster right now. thanks

 

i checked and nothing between the MC and booster. its all good. maybe i need to re-check brake lines behind the wheels.

since all the fluid leaked out, if i fill it up and have someone pump the brakes while i check the lines, fluid should start to leak out every time the brake is depressed right?

 

i just went through this, check and see if you have a puddle of brake flluid under you backseat, if you do then one of the llines coming from the prop valve to the rubber lines in back broke

 

If your master cylinder runs out of fluid you have to bench bleed it and bleed the brakes.

Look it up and do it. Probably your problem.