For those of you with 300Ds (NOT 240d) made before June 1983, this may interest you.

I was searching therough AllData here at DADC and I came across this interesting TSB for the Diesel models.

Bulletin no. 20/24
Date June 1983

Since febuary 1983, a modified visco clutch (Higher viscosity), 9-blade plastic fan, smaller water pump pully, and shorter v-belt have been installed on engine OM617.951. (Installed on all OM617.952 as of July 1983.)

The waterpump/fan pully is now 0.9:1 (149mm) insted of the old 1.09:1 (176mm) to the crank and requires a serrated 9.5x1000 belt insted of a 9.5x1035 solid belt.

Due to the lower pully ratio and higher visco clutch, the fan may now spin at 4000rpm max., previously 3500rpm. (Don't even THINK of installing the new pully or clutch with the old metal fan ).

Part #'s:
Pully: 617 205 09 10
Clutch: 000 200 19 22
Fan (9-blade): 110 200 03 23
Bolts (To mount the new fan.) (18x15 vs. 8x18) 000933 008131
Washer: 000433 008406

These new parts should make a very noticable difference in cooling for and 1983 and before D.