If you take out the thermostat, it will overheat for sure!

Check the system for pressure when hot -- it's somewhat likely that the pressure cap on the reservoir tank has gone bad and is not holding pressure anymore. This will cause overheating because the coolant will boil in the head, and the steam won't tranfer the heat to the rad.

Also, make sure the visco clutch is working. Fan must move large amounts of air and "roar" when the rad is hot, if not, replace. Easy way to check is to shut the engine off while hot (90C or more) and watch the fan. If it turns more than one revolution after the engine stops, the clutch is bad.

You may also have a bad radiator. Best way to check that is an infared thermometer, make sure there are no "cold" spots in it.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!