My 95 Accord started showing this symptom:

After driving the car for a while (specially on HOT days) when I come to a stop on an uphill the brake pedal verr slowly begins to sink under pressure, It doesn't seem to go all the way down and if I pump it comes right back up. Also, I don't notice this problem if the car hasn't been driven for a while.

What is more likely bad brake line / air in the lines or the dreaded Master Cylinder?

Your experinece is appreciated.

 

If the brake fluid is not low due to a leak, then I think you have a master cylinder problem.

EDIT: Also, has any brake work been done on the car lately?

 

Thanks PAhonda,

Yes I had a my brake & clutch fluid replaced, the mechanic said he used vaccum pump to bleed the brakes. I gues eiher he didn't get all the air out or somehow damaged the MC?

 

It could be possible that the MC got damaged if he pushed in the caliper piston forcing fluid into the MC. Not sure how he removed the old fluid.

It is more likely that air got into the brake lines. I would take it back to see if you mechanic will bleed the system again.