SC Brake issue

[MBAtarga]

I drive my SC only periodically and have had an issue lately. I apologize for the length - if you hung around, I'd explain it to you in twice the time.

First symptom was a burning smell in the cabin that appeared within the first ten minutes or so of driving. I thought it might be an electrical issue and pulled over, popped hood, couldn't find anything in the fuse panel area as an issue. Seemed the fuel pump relay was a bit warm, but no other issues. Got back in the car, drove it a few more minutes and the smell dissipated completely.

Next time out a few weeks later, burning smell in the cabin re-occurs. I happened to be near an auto parts store and pulled in. Again, popped hood - no issues found. But then while kneeling lower, I realized the smell was strongest just above the wheel well - then it dawned on me. Must be a sticky caliper that was over-heating. Got back in car to drive home, and the brake pedal went straight to the floor when I went to back the car out of the parking space. I drove in the (almost empty) lot for a few minutes - the pedal would be firm after a few pumps. Then I would start out and stop again - pedal would be completely soft. I figured the heated brake fluid (standard DOT 3) must have boiled and got air in the system. This was the first time the brake pedal had acted in this manner.

I had rebuilt calipers with new pads, turned rotors, etc. about 10 years ago. I decided to order caliper rebuild kit for the front (ordered from Pelican Monday, parts arrived in ATL GA before lunch today - that is fast 3 day shipping! ) and just finished installation. I also replaced the soft brake lines. Brakes were bled and pedal felt somewhat firm in the garage. Took the car out for a spin - pedal goes straight to the floor in the driveway.

Seems consensus is this is a bad master cylinder symptom based on pedal behavior - but would that explain the symptom of the sticking pad/burning smell?
Edit - just realized I did not include that the dash brake warning light is also on.

[kimlangley7]

You could have experienced both failures
> dragging brake caliper
> faulty master cylinder

definitely the burning smell from the front = dragging caliper - I had a bad caliper on my sons M3.. would run OK for awhile > then drag... then ok and more drag... I'd spit on the rotors to see how hot >> and sizzzle... rebuild of the caliper > cheap - just a few gasgets...

I'd replece the master cylinder > bleed the whole system again and see what happens

[johnsjmc]

Perhaps your rears are dragging too. Could you stop the car at all even with the low pedal? If so ,then rears going away would leave a low pedal and still stop the car with your rebuilt fronts.