A couple cans of brake parts cleaner. I think you can do this with the rotors on the car, although I've never done it that way (I clean them first), but you will have to remove the pads and spray all the cosmoline off the face of the pads.

Spray the cleaner over the friction area of the disk and let it run off, then repeat. Wipe with paper towels. Make SURE you get it all off the back side of the rotors.

It will EVENTUALLY all burn away, but the brakes will never work properly.

In the future, flush off the cosmoline just before you mount the rotors, only take a minute or two. On the rears, don't forget the parking brake drum surface on the inside!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!