Was a super hot day today. Well over 90. Drove my car down to a shop to check on somethings - about 35 minute drive. Everything was fine. On the way back, aside from the minor starting clitch, my brakes seemed like when i stepped on them, the car would just slowly come to a stop. Peddle was a little spongy but didnt sink. I just had new ss lines and 19mm master put in. New fluid too about 2 months ago. Got the car home, pumped the peddles for a bit and then it seemed to brake ok again. Is it likey its just air in the lines? Funny how it took 2 months to start a problem. Reservoir is full and no leaks. Any advice appreciated.

try adjusting the rear calipers if the pedal is down.

you might have a caliper sticking and getting the fluid hot enough to boil.

flush the system with fresh fluid and start from there. you might have a bubble stuck in the proportioning valve. bleed there first.

Could the hand-brake have been on, even slightly? That will get the brake system hot enough to develop a soft pedal.

-Lawrece

The emergency brake was off. the red light would of been on. The other thing is, I had the car up on jack stands, wheels off. I noticed with the front rotors, there would be a very slight rubbing with the pads when i turned it by hand. I planned on doing the rotors bearings and pads soon. Would that indicate a sticky caliper? had the emergency brake on and car in gear. dont think that would make any dif though. Do the calipers need a rebuild? they dont leak.

There is a good chance you had some residual air in the system after replacing the MC. Bleeding the brakes is easy, and gives you a chance to inspect the calipers at the same time. After you bleed a caliper, but before you add fluid to the reservoir, remove the pads and retract the caliper pistons, then pump the pedal to push the pistons out again. That way you will find out if a caliper piston is sticking. Also inspect the rubber piston boots for cracks. If a boot is cracked you definitely need to rebuild.

I would guess an air bubble left in the system expanded in the heat and finally worked its way to the caliper.

Jeff