You're saying when the engine starts, pedal goes to floor, but with engine off, it's fine?
That is usually sign of brake booster issue, but there are better ppl on the site for that diagnosis. (Never had an issue w/that.)
But, as I don't believe in automotive coincidence:
How to Bleed Brakes:
Note that many people disagree with my method, so judge for yourself.
Taught to me by semi-famous Toyota engineer, who built championship winning cars and bikes.
1. Get Sears brake bleed kit (canister, hoses, adaptors for bleed valves) and their hand vacuum pump. Kits there have both components. Inexpensive.
2. Pour a little b/f in canister, hook up hoses and use the tightest adaptor you can.
3. Pump vacuum to 20-25” with bleeder valve closed.
4. Tap caliper with small hammer or similar. This releases the air bubbles clinging to the caliper into the stream. WHATEVER method you use, DON’T skip this step.
5. Open bleed valve.
6. When vacuum is almost (but not completely) gone, close bleed valve.
7. Check level in master cylinder. Do this often.
8. Repeat as needed.
Benefits:
*Never got a firmer pedal using any other method.
*Requires only one person. Your wife/so will thank us both.
*You will not be pushing the piston in m/c into the rough area normally unused, thereby not prematurely wearing that seal. (Clutch m/cs are always used to full range.)
Note: On my Elise, I needn’t even remove the wheels.
Yeah, yeah, people use pressure bleeders, but my racecar mechanic friends don’t like these.
Yeah, I know about speed bleeders.
The above is my opinion. No responsibility for screw ups, injuries, maiming or deaths.
Take it, leave it. OK with me.