I have 1988 300e that gets warm when idling or in slow and stop and go driving. Fluids okay. Do I start with water pump or what else to investigate. Thanks for any input.

The fan viscous may be the problem as well as a plugged radiator or even a t-stat.
Check the radiator by running the engine till warm then shutting off the engine and feeling the engine side of the radiator for "cold spots". If present, replace the radiator. Check the viscous by running the engine and raising the engine speed for 40-50 seconds. The engine fan should increase and decrease in speed when the viscous engauges and disengauges. The thermostat is a good item to replace just for good insurance.
good luck
Turbo herb

Also be sure to inspect the aux fan for proper operation! They blow fuses often and if you run the A/C, the engine will run on the warm side with no aux fan.

------------------
Benzmac:
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

To all. I have bad experience with water pumps. My wife had a Toyota which she bought brand new. After a couple years during scheduled service at the dealershop someone replaced coolant with Presto or some other stuff. The result... water pump blew up two years later at 50k miles. The same with my MB. Previous owner filled the cooling system with this green stuff. The result... the water pump blew up. You should see it how rusted it was.

Word of advice! Don't save money on coolant. Even if you service your car at the dealer insist on filling up with original coolant.

Mikeb,

I saw a water pump having the shaft came off while driving due to a worn-out bearing. The car was only 32000 miles old. The premature failure of water pump mostly caused by unbalanced fan or the fan belt adjusted too tight. On the older car, after a radiator flush, the water pump sometimes starts leaking. Was your water pump actually "blew up" sending pieces everywhere?

Per one of the MB service bulletins issued a while back, the engine may get very hot (I do not remember the tempurature reading) in slow traffic and it is normal as long as the cooling system is in good condition (proper mixture, pressure, coolent level, air flow, coolent flow, etc.)

David