The car is the 87 190e 2.3 with 250k miles. I know the head has been off the car but how long ago, is unknown.

I have been chasing this problem now for almost a year. On the road the car’s temperature is always just above 80 degrees. In stop and go traffic the temp will creep towards 100 and sometimes goes higher. Sometimes the electromagnetic fan kicks in, sometimes not. Most of the time it does, but if not, then the AC fan kicks in high speed.


This is what I have done:

-Changed the radiator cap to a 140
-Replaced the sensor for the electromagnetic fan.
-Replaced the thermostat
-Replaced the engine temperature sensor for the ECU
-Adjusted the mixture to that it ranges between 70-74%
-Flushed the cooling system
-The coolant mixture is 50% water, 50% coolant

Today I replaced the radiator with great expectations of finally curing the problem, only to see it get too hot, almost more so with the new radiator than with the old one?!?!

Questions:

-Should I remove the thermostat and run it that way?

-Am I just staring a head gasket in the face and not recognizing it?

-Do I have an air pocket? If so how do I get it out?

-Is the mixture still too lean?


Your help is greatly appreciated at this point ….

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Your coolant temperature behavior sounds perfectly normal to me. There is nothing to fix.

Is the fan clutch electromagetic of themostatic. My '84 2.3 had an electromagnetic clutch, but I though later 2.3s have a themo-clutch like my 2.6.

I assume your car also has an auxillary electric fan.

On my 2.6 the mechanically driven fan's thermo clutch tightens at about 100C, so in stop and go traffic it will get up to 100. In hot weather stop and go traffic it can get up to 105C, which is where my two auxillary electric fans engage at high speed. This rapidly cools the engine to about 100 where they disengage.

The electrics also engage at low speed based on A/C demand. The car will actually run cooler in traffic with the A/C on since this operates the electrics enough to keep the temperature from going over about 100C.

Duke

2.3 had the electro magnectic fan into the 90's. I agree behaviour above sounds perfectly normal.
The fan just idle-spins until just over 100 and then kicks in straight to full. Its not a gradual build like a clutch fan hence he high temps. Some people have put a resistor in the fan switch to force it on at a lower temp.

Thanks. I'll run it today and see how hot it gets.

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

What kind of thermostat do you have on the car? If it is a Behr Thomson than replace it with one made by Wahler 75°. Brake off the check valve on the thermostat.
Fill up the radiator by taking off the top radiator hose and fill through there until you see the water come up the water pump. This eliminates the possibility of air pockets in the radiator, assuming you have an original Behr radiator.
Yes, you do need the thermostat. Without the engine runs too rich, you will loose a little of your fuel mileage, and it can damage the catalytic converter over extended driving without the thermostat.
Good luck;
Jean

There is nothing in haasman's original post that indicates a problem with the thermostat. His cooling system temperature behavior is normal. There is no need for him or anyone else to "re-engineer" the cooling system.

A lot of guys seem to think that the themostat should maintain constant coolant temperature like the themostat in your house maintains near constant air temperature. This is not true for any car. The thermostat establishes the minimum operating temperature, and it is not fully open until about 10-15 degrees C above the initial opening temperature when the valve just begins to lift off the seat.

The upper end of the normal coolant temperature range is determined by radiator heat transfer capacity and air flow. The electric fan(s) doesn't engage at high speed until about 105C (and this should rapidly drop the temperature to about 100), so the normal operating range is about 80-105C (176-221F), and a temperature range of 100-105C in heavy stop and go traffic, especially in hot weather, is normal. Only if the temperature regularly starts pushing above 105 should one be concerned that there may be a problem.

Duke