Newbie with a coolant dash on
 

Hi,
New to this forum, not new to Mercedes. I have a 1999 ML 320. The coolant dash light comes on after 5 minutes of driving and then will go off. For a 20 minute drive, the light may come on three to five times. The reserve tank against the firewall is full. No leaks that I can see. The temp is running at 90 degrees or a tad less. The water pump was replaced about 6 months ago, that was a drip leak back then. My mechanic pressure tested the coolant system, no leak. My concern is I smelled a whiff of coolant maybe twice in a month after parked and turned off. Again, no leaks. The mechanic was saying it may be an old radiator or heater core. Any suggestions? Thanks.

Try removing the cabin air filter and see if it is wet with coolant.

Thank you I think you got it.