hello. i posted this in diesel discussion but thought i'd fly it here as well.

the other day, just after it turned cold here, i started my '84 300D and let it idle for 15 mins to warm up. i turned the heat on as well, jumping it with the defrost button. when i came back to the car the engine temp gauge read over 100c and cold air was still coming from the vents. i had a short drive to get home (3 miles) and a little space on the gauge so i figured i'd start driving and see if the cold air rushing through didn't bring the temperature down. after maybe a 1/4 mile the temperature gauge dropped fast (too fast for the cold air theory - i was in a 35mph zone) and heat started pouring through the vents. i was relieved and drove homeward. one more time on the way the heat rose onthe gauge and the cabin got cold.

in the Diesel Discussion forum i received suggestions of Monovalve problem or fan clutch and thermostat. the thermostat seemed to make the most sense so i bought one and replaced it.

but no change!

where do i go next. i was told the Monovalve didn't have anything to do with engine temperature (as in overheating). and my big fan runs fine. when should the little one kick on?

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1984 300D "Brown (and Blue) Betty" Over 200k but the odometer isn't counting