Well my 10/84 build 300SD has the updated style condenser and larger aux fan from the factory. BMW also did this around late '85 for their E23s due to lame cooling.

ALSO late 617s received a different water pump pulley, smaller in diameter to overdrive it, so it not only cools the motor better but also spins the fan faster moving more air... making the A/C work better. I think this started in '83, but do your own research on this.

MB also changed the main cooling fan, mine came with the plastic fan as opposed to the earlier aluminum fan. I think the earlier fan cools better as it is on the V8 models as it simply moves more air. I would take a wild guess MB installed this along with the 2.88:1 diff in 1985 to maximize fuel economy from the 617 and free up a bit of power.

I would like to install the earlier fan for more airflow for A/C at low speeds due to my climate.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

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