you don't need to remove radiator, but be careful not to puncture it with tools since you don't have much space especially when removing fan. do yourself a favor and replace it before it gets below freezing. it is labor intensive job, i know it took me almost all day, but it was the most difficult job i had done so far at the time. if i had to repeat the process would probably take me 4 hr max. considering the age i recomend replacing upper/lower/bypass hoses, thermostat, and serpentine belt since you will have the old one out. use zerex g-05 coolant or mb labeled one and use 50/50 coolant/distilled water ratio, that is what mb recomends. if you live in very cold winter area the max mb recomends is 55/45. drain radiator before removing water pump. also don't get a very cheap water pump from ebay. i think autohaus has graf pump for good price. all parts should cost you a little over $200. http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Engine/104/20-2100.pdf
I replaced mine without a need to remove fan. Just needed to remove fan shroud, belt tensioner, PS and water pump pulleys.
Recommend great care with loosening four allen heads holding pump to block. Round one out and it will be hell. Especially the forward lower one.
For future info - ALLDATAdiy does not have any instructions for the water pump removal / re-install, and I have the subscription for a '97 S320. It has just about everything for the pump except instructions. There's one diagram that is the same as what's on the 1st page of tirona's link.
That's my major complaint with ALLDATA - some of the more routine things just aren't there.
On the other hand, the water pump removal doesn't look too hard, and being on top makes it so much easier, and you can see everything right away. My '73 220D's pump was behind a large A/C compressor bracket, which fit ultra snugly.
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