I replaced front brake pads today! Thankfully, I did not notice any leaks on calipers at this time.

The pads I removed should have tripped wear sensors, if the sensors were working, as 2 pads (inner ones) were ground down about half-way across that little hole in a pad where sensor lead goes.

Turns out, sensor harness cables are bad on both sides! I do not know how they got mucked up this bad, but the cables are severed near their spindle mounting. As I said, the dealer alerted me to this, while Brian suggested it could simply be damaged sensors - unfortunately it's the $50-a-piece cables. The previous owner must have somehow messed those cables up because this is the first front brake job in 3.5 years that I had the car.

I ended up installing pads without sensors because what's the point with the cables broken... When I have money, I will fix this as it was meant to be :-P

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84 300SD - bought in April '06 with 237,000 mi