Snapped Belt, Strange Coolant Leak
 

W124 OM602 300D 2.5T

Driving home from work the car began behaving very erratically, intermittent P/S problems, all the dash lights blinking, temp going up...

Pulled over, found the serpentine belt was shredding itself and had come off of the fan pulley. Got it back on, drove home, temperatures seem fine and no strange coolant smell indicating a head gasket failure...

BUT, when I had the car pulled over to fix it, it drained some coolant (300 mL?) from right behind the front passenger's side wheel. Looking under the hood, I can't find any source for the leak. The coolant expansion tank is visibly drained.

Any ideas?

Seems like the water pump has seized, heating up the coolant into the overflow tank in the front passenger fender, and forcing the belt to do what it did.

I was worried about that, too, but after getting the belt back on, the car ran at normal temperatures the rest of the way home. New belt is on (I found that leaving the spring on was easiest) and the car is running smooth and cool.

When mine shredded the belt (alt locked up) and the water pump could no longer turn it did the same thing. The coolant was bubbling in the expansion tank and it was throwing collant every where. after it cooled down I went out and looked for a busted hose, but found nothing wrong. Head gasket is fine. I had to drive it to the next exit after the belt shredded and I had the temps up to 120 but it never touched the red line for a few minutes. I put on a new belt, flushed the entire cooling system, refilled with the correct antifreeze and good to go.