Agree on air purging. After filling my 1984 300D with Evans Waterless Coolant, after driving 6 miles on the freeway, the dash temp gage suddenly began climbing fast. I pulled over right as it hit the 120 C redline. I had to add a half gallon of coolant to top it off. No coolant loss and no more overheating, even climbing the Sierras on a hot day. I don't think the engine really got that hot, but rather the temperature gage shows hot if in an air pocket.

Mercedes wisely designs this tank to self purge however the heater has a coolant shutoff valve so one needs to be aware of this .

In manual HVAC you simply turn the two heater dials to maximum heat .

In the other versions you need to let the engine fully warm up before the heater core fills and the thermostat opens .

Time is all this takes .

Some idiot used RED RTV in my brother's old W126 and apparently ran the engine before it was cured so there was a 3' long string of it in the surge tank's upper (supply) hose ~ we were 3,500 miles from home when in frustration I began taking the cooling system apart and found and removed it .

I used to have a photo of the long red snake lying on the fender .

Once that was out no more unexplained coolant loss .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better