Just thinking this through, there is one fan for both the radiator and the AC condenser. The fan generally turns on when the engine temperature gets to 95 deg. C., or when the AC gets turned on. It's possible that your engine temp is at, say, 90 Celsius, which is a bit higher than normal ("normal" is 80-85 C), but still well within safe limits. That can happen when you are, for example, doing a lot of in-town driving.

How much above normal is the engine temperature? What's the temperature reading on the thermometer?

 

I did connect a scan tool in the OBD2 port and started the car, the temperature started going up and up until it reached 98 degrees and at that point, I felt it was too high and the fan still didn't turn on, I turned on the AC and the temperature decreased. just to let you know, the car was parked at the time.

 

Let it go to 105 and see if it turns on

 

I don't think I should wait till 105, the fan should be spinning way before.

 

Yes

 

Yep, normal.

 

Here is how fan behaves with ac off. Engine hot at idle. Fan comes on at 95C, turns off at 93C. Demand 13.3%.

 

With ac turned on demand jumps to 40% instantly and goes higher to maintain refrigerant pressure at 14 Bar. Ac performance quite good. Evaporator temp at 2C.

 

Does anyone know if the W220 has procedure not in the owners manual to test the fan and actuate it to 100%? A W210 will run the fan(s) on high if the left and right "AUTO" buttons are pressed for about 10 seconds. Repeat to put system back in automatic.

 

Does anyone know if the W220 has procedure not in the owners manual to test the fan and actuate it to 100%?

Definitely has that option in ME Actuations on SDS as do all MB's with PWM Fans.

 

Yes 10% to 90%

I have never used the 'Button Dance' function on HVAC, didn't ever really see the point as SDS takes us way more in depth if there are HVAC issues, but you may well be right, it may be an option to test Fan in those menus, I just simply don't know ......................

However a Car with a properly functioning Fan should have no problem idling all day even in hot climes, I do believe the Fans are programmed not to cut in until coolant Temp reaches circa 95c, and even then it is only something like 20 to 30 %, if Temp still rises it steps higher incrementally, if temp falls, it cuts out (IIRC circa 88c)

HTH

 

Perhaps either engine oil or transmission fluid is being forced into the cooling system. The fact that the sludge build-up continued after the radiator was replaced greatly lowers the odds of the problem being transmission fluid, as that problem is usually a leak in the in-radiator transmission fluid heat exchanger.

 

Thick yellow stuff is engine oil . You have a head gasket leaking oil into the coolant . I had the same problem with a s320.

if you don’t change the head gasket it’s going to blow your radiator apart with pressure , I would leave the radiator cap on loosely so excess pressure doesn’t form

 

More likely oil cooler....