I'm having a cooling issue with my 93 400E w/130k. Car/Engine is in great shape, but I'm noticing that during traffic my car starts to overheat. I'll turn on the heater on and it quicky cools to it normal operating temp.
I realize that summer is over, but would like to solve this problem I've been having over the past few months. Here are a list of items I've replaced so far:
thermostat
radiator
new fan clutch (NOT CHEAP)!
radiator overflow bottle
resistor for aux electric fans (big white restitor located next to LH headlamp)
the sensor for the aux fans (black plug with 4 prongs - I haven't replaced just yet cause new sensor is not keyed like old one BUT has same part #)

- I've notice that the aux fans DO NOT kick on, so that is why I started looking into resistor and sensor. There is a relay that is located in fuse box, but I removed cover to inspect and relay looks good, plus I tried to manually activate and still fans will not kick on. BOTH fuses are ok: 1 located in fuse box and the 1 outside fuse box.
- I just can't seem to solve this problem, SO, i'm curious if any1 else has had this problem and have any suggestions/solutions. I surely would appriciate any help, thanks in advance.

 

I have a similar problem with my 92 300e. Only one of my auxilary fans was working. After testing for power at the plugs, and reversing power leads to the two fans, I determined the one fan that did not work was bad. I replaced it with a new one, and both fans work. Unfortunately, the car still tends to run warm, especially in stop/go traffic. I understand this is a chronic issue with this chassis.

 

Have you changed your thermostat?

 

Thanks for the replies guys/gals.

-I just finished testing (hooked them individually to an alt power source) both aux fans and both work just fine.

-I may be leaning towards replacement of the fan relay, pn # 0015428219. Although I disconnected and took cover off. Relay set-up looks clean and new like; can't seem to see nor smell anything burnt. I'm a little annoyed at the thought of having to buy another item and IT not being the problem. What the term for this, shotgun method.

I've tried searching for info on this subject on other forums and I did come across someone mentioning that the cooling system has to be bled. IS THIS CORRECT?? I remember having to bleed a BMW 325i but a 400e? I searched and couldn't find a bleeding screw. Anyhoot, on my way to the local dealer.