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 quickly 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 appreciate any help, thanks in advance.

 

Have you checked the length of the wire for breaks? Have you tried pulling the fans and making a temporary circuit to see if they'll come on with the independent power source?

 

The fans are essential in traffic in the summer, especially with the A/C on. Whatever you have to do to get them working, do it. Jump some power to them directly to check the motors, then work from there to find the problem. Could be the temp sensor, or maybe as simple as a bad wire. Best of luck, let us know what you come up with.

 

It was a bad wire for me.

 

Do they come on when the AC is running? The compressor will run for a bit with them off, but in mild or hot weather the fans will come on shortly after the compressor. I always use my AC is warm weather so the fans were always running.

 

I had a similiar problem.

Turned out to be the relay which is located in the Fuse Box.

 

Grab the round head of the fan(s) and spin it...does either spin freely? They should.

This isn't common but both of my fans turned out to be dead at about your same mileage , happened to others I know too with the M119 motor...find the power connection plug for them and hook up power from a battery directly to the fans to see if they work. Individual fans new are or were about $175 each from MB.

 

Wow thanks all for the replies folks.

-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.

 

Yep, throwing money at it fixes things ...eventually ! The good part is that most everything gets fresh and your good for another 10 years or so. The saying goes; I think...'there is no cheap Mercedes' and while the M119 is a great engine in a great chassis/design, it isn't with out its problems.

Has your car been overheating and/or bleching its antireeze?
Its super easy to bleed the M119...to drain there is a spigot at left bottom, usually with a red cap, then there are 2 blocks drains if you want to go all the way. Drain the overflow tank that's in the right fender too, at least check it by going thru the inner fender liner. Re-fill with Zerex or the MB stuff (gl-5) and distilled water mix and let the car get up to temp by running with the overflow cap OFF. It'll get good and hot and will 'burb' and 'suck' fluid several times...add as necessary. Took me about 30 minutes to purge the air on my M119. No need to have a dealer do that IMO.


Hope you're back to enjoying the car soon !!