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I've never read of a case just like mine -I've changed the radiator, the engine, the fan clutch, the thermostat and the coolant, and learned a lot about overheating in my '87 240 wagon. Now overheating only occurs at over 80 mph on a hot day.
The most interesting thing I've observed is that overheating is less, with the heater lever switched to FULL ON, even if airflow thru the heater is off (no blower on, air recycle ON). This suggests that at least part of the problem is water pumping related, probably volume and velocity thru the radiator.
I've also observed that during times when overheating occurs at 60 mph, it can be made to occur by downshifting and driving at 45 mph at high engine revs. This suggested either water pump cavitation or fan clutch.
In any case, removing the year-old brand-new NAPA replacement fan clutch and installing the 275,000 mile old, used clutch assembly from my '82 240 wagon solved most of the problem. The engine now roars on accelleration, I'm sure my gas mileage will drop, but the temperature stays below 1/2 gauge at 70 on a hot day in Florida. I have been running for the last month without a thermostat, but will probably replace it as the next step.
If you have read this far, you will be interested to note that the final change (fan clutch) was suggested by driving a full day with NO fan at all. Bummer! My 240 overheats like mad at 60 mph with no fan. There appears to be very little or no speed-based ram air effect on this particular car. I am accustoimed to setting up race cars with no fan at all, but have never done so with a condensor in front of the radiator...
Please, can someone point out the posting where someone measured air flow or pressure thru the radiator and temperatures around the radiator? I've heard it exists, but cannot find it.
Thanks for listening!
=>Jim<=
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