Recently I've noticed my 1985 Mercedes 300DT (300,000 miles, 2nd owner) is running a little hot. Of course, it's hot in Atlanta in August.

Today I ran a little test ... Ten miles in the heat of the day WITHOUT A/C on. It averaged around 90C, with small spikes going up near 100 when stopped at intersections.


Did the same test this evening; same route, same distance -- but the temps were much cooler in the evening (around 80 ambient temp). I got the same results: The car averaged around 90C with small spikes when stopped at intersections. Throwing on the defroster does drop it down to about 85C.


Here's why it matters ... in two month's time, I'll be driving this ol girl 2400 miles from Georgia to the West Coast.

I've purchased a new thermostat, new radiator plug and a new cap for the radiator expansion tank.

My question is this ... is it too risky to run a proper flush with a long trip looming? Would it be better to simply drain and replace the coolant (which I believe is green) when I replace the thermostat?

(In the three years' I've owned the car, I have not flushed the radiator and cannot attest to the last time it was done. The radiator in the car does not appear to be original, meaning 30 years old.)


Any and all advice greatly appreciated.





... And before you think driving an '85 W123 across country is foolish ... my wife will be driving her ML behind me. Now THAT is risk.