Hot Idle!

[Tony]

OK, here's my dilemma. I have a 68 250sl recently rebuilt engine, auto.trans, radiator, new water pump, thermostat....Runs great. Yet, after driving for about 20 - 30 minutes, either on the highway or off, if I end up in a bumper-to-bumper traffic jam or bridge opening exceeding 10 minutes, the temp gauge begins to rise fairly rapidly. It has not gone quite to the 'red'marker, but enough to get me panicky! Am i missing something here? Any thoughts would be apreciated.

Tony
Miami, Florida
trodriguez@broward.org

[BHap]

sounds like a fan clutch to me....  roll some newspaper up and with the car idling and warmed up, try to stop the fan with the newspaper...  if you can stop the fan, the fan clutch is bad....  had this happen on an old bmw, I think the Mercedes fan clutch works the same...

Bob Happe
Pittsburgh, Pa
1970 280SL, white/black 4 speed

[waltklatt]

The newspaper trick is the trick to do, also check to make sure the timing is correct too.  Advancing the timing might cause higher temp running.
Also is the thermostat the correct one?
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

[J. Huber]

Walt, by correct one, do you mean not only that it is a 113 thermo but that it is also the right opening degree for his climate? I would guess the 79 would be best for Fla?

James
63 230SL

[ja17]

Hello Tony,

Also try the heater test. Turn the heater on full blast next time the car begins to overheat. If the temperature drops dramatically, the fan clutch or radiator could be bad. If the temperature climbs higher at highway speeds, the radiator is usually the cause.

Internal engine problems can also cause oveheating. A cooling system which "over pressurizes" or builds up pressure too soon can indicate a damaged head gasket which can allow hot combustion gases into the cooling system.

We will hope for a simple fix! Start with the cheap and easy things first.

Joe Alexander
Blacklick, Ohio

[Tony]

Thank you folks very much! I will do the 'newspaper check' and see if the thermostat is a 79. Will advise.