so my seven has been sittin for a while... and i go to start her and take it around the block and realize i have a really mushy brake. so i pump the hell out of them and they stiffen up.... then mush. ok i get home shut it off pump the pedal and it stays firm. start the car and mush. we tried bleeding the brakes and wasnt gettin and bubbles so im think master cylinder. any thoughts?

 

in addition to bleading your brake pad wear can contribue to this feeling. Check both front and rear pads, ensure you are not getting low. After that, you may wish to flush your entire brake system just to be sure. If you do decide to replace the master cyl, i suggest the 929 unit. it won't be too mushy with that Be advised that in order to replace the master cyl. with the 929 unit, you will need to fab a brake line. I recommend using stainless steel for that brake line, but others have used flexible braided lines.

 

pads are brand new less than 1000 miles thanx for the info tho

 

first off, key off engine off, pump the pedal 5-10 times, it should stiffen. After that, turn on the car, it should go back to normal. If it sink all the way down, ur diaphram on the vacuum / hydraulic brake booster is faulty. If the brake booster is okie, then pop the hood, have some1 open the reservoir, you turn on the car and pump the pedal slowly. Have the assistant observe the fluid moving pattern. As you pump, it should make a fountaining effect, and when you retract the pedal, it should make a swirl. If the pattern are reversed, you need to adjust the pedal push rod forward because the seals are not in between the compensating port and the inlet. If that doesnt solve it, and you already flushed the system following the manufacture directions, it will be the primary seal in the primary piston @ the master cylinder.

Sorry to write all these long steps, didnt want to buy a new master cylinder becuz it could be the brake booster thats @ faulty from what you described. But yeah check it out and let me know what I can help a fellow out =)
-Eric

 

forgotten to mention, you might have a leak somehwere in the brake line, having air into the system. Do a brake line inspection and see any leakage around the brake system.

 

i was worried about the brake booster as well but in all my years playin with cars ive only seen a few bad ones. i appreciate the info ill have to check it out tomorrow.

 

not a problem, let me know how it goes. I am pretty confident with the brake and abs system. Because I've just brushed up getting ready for the ASE certification on brakes =)