I did it on my car about 2 years ago. I wound up jacking up the car, removing the passenger tire, air filter housing, and maybe even the heat shield panels. That gave me enough clearance.

It's a PITA. It made me wish I still had my w123 which has the thermostat conveniently located at the top area of the engine.

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2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
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'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold