Expert: Roland Finston - 7/1/2009

Question
Temp Gauge goes to full hot after only a few blocks of driving. Anti-freeze is topped off , no visible leaks seen under car or in engine bay (hoses all seem OK).

Answer
You may have air trapped in the cooling system which is effectively preventing the coolant from flowing. A few block of driving sounds very quickly? Here is how I responded a few minutes ago to a similar question:
"Sudden Overheating
Question:  Hi there-
I have a 2005 Sebring Convertible, 2.7 L engine. The car started overheating while driving home from the gym today [rainy/overcast around 80 F].  I can't find any leaking fluid, but lost about a gallon of coolant through the overflow.  No cracked gaskets, overflow cap looks fine.  I checked the fuse for the radiator fan and it's fine.  Any thoughts?
Thanks so much in advance -
Jim
 
Answer:  Hi Jim,
It could be the thermostat is stuck closed, or the radiator is plugged up, or possibly that you have a head gasket leak and so the coolant system is being pressurized due to the compression of the pistons being 'felt' in the cooling system.
Was this associated with overheating or did it come on very quickly after a cold start? If the latter, I would be suspicious of the head gasket leak. See if you get excessive white smoke from the tailpipe when you start the engine from cold, as that is the tell-tale, and also listen for early bubbling sounds in the cooling system within a few minutes after starting the engine, another sign of that same source. Also look for foam/cloudy engine oil.
The radiator should be about equally hot comparing the side manifolds with one another. One side cold would suggest that you don't have good cross-flow.
While the fan fuse is good, did the fans come 'on'.
Those are the possibilites that come to mind. Let me know what you observe.
Roland"

So let me know what else you observe based upon this response. There is a special filling funnel/technique used on the 300M because of its 2-compartment bottle.
Roland