Okay I'm having brake issues at this moment with my 1995 Honda Accord LX 2.2 4 cylinder. I already am sure I need to change the MC because it's not holding fluid and drains in about a day and a half, but see no signs of leaks. Which brings me to my next point if I change the MC should I change the booster as well? I've read how to diagnosis and when I pump the brakes when car is off and start the car the pedal falls (which appears to be good). Then I don't see any visible vacuum leaks in the hose when I spray break cleaner on along the line. The one diagnosis that I don't understand is when you pump the brake once or twice and turn the car off it says that it's suppose to stay in the same position, and it does but starts to sink after 5 seconds.... does that mean it's bad?

 

If you pump the brakes with the car off and it looses pressure, i would assume its due to a leak of pressure from lines or MC. Have you check all the caliper bleeding bolts to be sure they arent loose? Or bleed them a couple of times to see if they have any air in them?

 

This, brake booster has nothing to do with it. Your brake booster is fine, only thing that would affect is pressure needed to press the pedal.

 

When i pump them brakes when its off it holds just fine. ill have to check the bleeding bolt, i don't know why i didn't think to check it. Ill check it and update as soon as i get the opportunity to get it checked out.

 

i was just concerned that the MC is leaking into the booster.

 

The brake master cylinder will leak into the car, above the pedal assembly. Take a look down there.

 

or leak internally and get sucked into the engine and blown out thru combustion.

none of this is ideal.