Our 09 MCs started having issues with the heater. It would blow hot air when moving and then cold air at a standstill. Brought it in to the dealer and found out it had a coolant leak and the temp sensor was bad. Since the MCS doesn't have any sort of temp gauge, I'm now wondering if it lost enough coolant to overheat/damage the engine? It's almost out of warranty and I'm worried that there's some hidden motor damage and the dealer is just going to fix the leak and replace the bad sensor and send us down the road.

This is only about 2 months after the car had a leaky turbo oil return line too. Anyone have these similar problems?

 

Well, anything's possible where fluid leaks are concerned. But unless the system was totally devoid of coolant (and the dealer performing the diagnosis/repair work should be able to tell you, one way or the other), you should be fine. And if it was totally devoid of coolant, you probably would have known, since the engine would have quickly become so hot that it would have started smoking...

I had a '90 Grand Am once that ruptured a transmission coolant line that ran between the transmission and radiator, the net effect of which was it was pi$$ing transmission fluid while I was driving (naturally, on the highway, a hundred mile from where I wanted to be). My first indication of problems was when the transmission started slipping. Fortunately, I pulled over and investigated before I lost all of the trasmission fluid, and ultimately saved myself a lot of trouble (and cash). The transmission was fine, and I owned the car for several more years before getting rid of it for unrelated reasons; never had another transmission problem.