190e overheats only when Idling for 20+ minutes
If anyone can answer this one you will be my Hero!!!!
car: 190e 2.6 1993
Problem: car overheats and/ or runs right beneath red temp line only when it idles for more than 20 minutes.
1.) replaced the water pump with an OEM graf water pump, changed hoses
2.) changed radiator fluid (60:40 anti-freeze to H20 mix),
3.)tried both the old Mercedes thermostat and a wahler thermostat.
There are no leaks in the system by visual inspection.
Operating temp when driving is just a touch above the 80 degree Celsius mark. No problems what so ever when the car is moving.
If I just let it Idle for more than about 20 minutes, it overheats or hits the white (120 degree Celsius) line (depends on the mood the car is in I guess). This occurs with the heater on, heater off or AC on. It seems like it warms up faster when the heater is on.
The Auxiliary fans kick on when the temp hits around 100 degrees Celsius, and does and adequate job cooling the radiator down (I can touch the radiator and it cools off when the aux fan kicks on).
If the temp gauge hits 120 degrees Celsius when Idling, I can rev up the rpms to 3000 and the temp drops to 90 degrees Celsius.
Some of my questions are as follows,
What else could be wrong?
How else can I test the cooling system?
It appears that the auxiliary fan is working appropriately.
I tried two different thermostats with the same result.
Could it be that the OEM (graf) water pump can not pump enough fluid when at Idle speed to keep the engine cool when idling?
How can I a mechanic look at this, and feel sure that I'm not getting screwed (e.g. what would be the normal number of hours billed to trouble shoot this).
Can anyone with a 190E (that is working well) tell me what happens to their temperature (e.g. what is the temperature range) if you let you car Idle for 20-30 minutes.
Again I'm desperate, and ready to blow up this car!!!!!