user001

two recent issues have arisen on my 2007 C280 4MATIC (91K miles). Outside temperature has been in the 90s past several days.
1. AC mostly works fine, but from time to time it starts blowing really hot air. If I turn it off, wait a couple of minutes and turn it back on, then sometimes it keeps blowing hot air, other times it returns to normal cooling.
2. In city driving in the hot afternoon sun, the coolant overheating symbol keeps showing up on dashboard and temp guage increases from about 85 to 100 degrees C. I drove around with an OBD scanner and checked the real time ETC data. In highway driving at 70mph, coolant temp remains around 84. In city driving, it creeps up to 105 at stop lights and the overheating sign comes up on dashboard. Coolant level is fine and there are no coolant leaks.

I was wondering if these two problems could be caused by a loose serpentine belt and if so, is this something I can fix myself?
Thanks in advance for responses.
Amit

slammer111

Best way to go is to pull over when one of the events is happening and pop the hood.

Are there any squealing noises from the belt?

If the belt is loose, the first thing that comes to mind is the tensioner.

Any job can be DIYed. That's why this forum exists. Couldn't tell you much about your particular engine, but on most (if not all) modern engines the tensioner is a standalone part which means it can be replaced.

acetaylor

Sounds like your electric fan is not working. When you are moving at speed you're getting enough air through the radiator and condenser to cool the engine and condense the refrigerant. When your are slow or not moving, not enough air is moved through the radiator and condenser for proper heat exchange. That's my two cents. Take it for what it's worth.