190E temperature problem

[jbadgio]

I hate to beleaguer this forum with questions about my 190E overheating, but this is the last time. Initially, I thought the car would overheat only when the AC was running, but this is not the case. Whether or not the AC is on, the car's temp will spike to 100 - 105 when the car comes to a stop. If the car is running, there is no problem. When the temp is running at 100 or so, it will quickly cool back to 80 - 85 when the car begins to move. What do you think the problem is? Help me get started in the right direction.

[4uky]

Have you checked whether the fan is working? Connect the leads to the fan motor directly to the battery and see if it runs...

[yal]

Which 190E? 2.3? 16v? 2.6?

[Duke2.6]

The viscous fan clutch or electromechanical fan clutch engages at 100C and the electric fans engage high speed at 105C.

With the A/C on it might actually run a little cooler, because the electrics will engage periodically at low speed based on A/C system demand.

In hot weather low speed driving, temperatures up to 105 C are normal, so there is probably nothing wrong with your car.

Once you get up to freeway speed the temp should rapidly drop to 90 or less.

If you aren't convinced that nothing is wrong, run the following test.

1. With the A/C off and the temp at 95C or less rev the engine to 2000 and note the fan noise, which should be very little, also feel the level of fan air flow, which should be slight.

2. Let the car idle until the temp reaches 100-102C then open the hood and bring the revs up to 2000. You should hear fan noise and feel considerably more air flow than in step one.

3. Let the car continue to idle until the temp reaches about 105 degrees and verify that the electric fans(s) engage at high speed. They should make a noticeable whinning/whirring sound and the temperature should rapidly drop to about 100 where the electric(s) will disengage, and the cycle will repeat until road speed is high enough to cause sufficient cooling air flow.

4. You can test the A/C fan function by tuning the A/C on max. Open the doors or windows with the coolant at 90C or less on a warm to hot day. Let the engine idle and check that the electric(s) cycle every minute or so at low speed. If not, the A/C pressure switch that controls the fan(s) is defective or there is some problem in the circuit like a connector or there may be some other problem with the A/C system.

If it works, don't fix it! This is typical cooling system behavior for all modern cars. Your car is not "overheating". With a proper 50-50 mixture of antifreeze and a 1.2 bar pressure cap, overheating does not occur until about 120C.

The only people who fret about coolant temperatures are those who have cars with calibrated gages like Mercs and Corvettes. If the car had an idiot light or a gage marked C and H you would never have anything to worry about, which is why some OEMs (like Toyota) won't install calibrated gages. They get too many invalid "my car runs too hot" complaints. Temps up to 105C/230F on modern cars are normal - particularly in hot weather low speed traffic conditions.

Duke