92 190E 2.6 Overheating Problems

[smk_texas]

Hi,
I have a 92 190E 2.6 with 92k miles. The engine overheats, (goes above 90C) when the car is at a stop light. Then when the car is in motion the temp comes back to normal. While at the stop light, if I put it in park and revvup the engine the temp starts to go down to normal. A mechanic suggested that the fan clutch could be the culprit. Put a new fan clutch and still have the problem. Last week I posted this problem in the forum and a member (JDUB) suggested that I change the thermostat. I did that and the problem is still there. The water pump seems fine because I see no leaks or noise coming from there. I also flushed the radiator using a domestic water hose last week when I changed the thermostat. There is no loss of coolant anywhere either. I am kind of stumped at this point. I might also add that for the first 30 -40 minutes of driving the temp seems normal. This overheating starts only after this 30-40 minute period that too only when the car is not moving. Any ideas or insight into this problem will be greatly appreciated to say the least. Thanks
smk_texas
92-190E, 92K

[Ali Al-Chalabi]

Temps over 90C are by no means considered overheating by Mercedes standards. The fan clutch does not kick in until the engine starts to see 100C anyway. Aux cooling fans do not kick in on high until 110C and cycle on and off of low speed with the A/C on according to refrigerant pressure.

Exactly how hot does the engine get at idle? These cars are designed to approach 100C even with everything functioning properly at idle. On a very hot day at idle with very high A/C load, engine temps around 110C would not be considered that abnormal. If it gets any hotter than this, then there is a problem.

[Benzmac]

If you are using the A/C, be sure that the auxillary fans are operating. IF not, you will have a warm engine.

Also, I have seen the radiators plug up from time to time.

[CJ]

The temp is not that high, have you tested the guage and the sender yet?

[smk_texas]

Thanks for the advice & suggestions. I understand that on a hot Texas summer day the temp go as high as 110c. What I don't understand is that it does this only when the car is at a stop sign. But, when I revvup the engine when at a stop light with temp hovering at about 110 -115C, the temp comes down to normal. I thought it could be a clogged up radiator but the fluid looks clean. Maybe I should remove the radiator and have it acid cleaned in pro-radiator shop. The sending unit tests came out fine and the auxilliary fans are operating normally as well.
smk_texas
92 190e 92K

[Ali Al-Chalabi]

The radiator may be restricting flow.

The temp comes down beacause the coolant pump and cooling fan are engine driven. When you rev the engine, there is much more coolant flow through the system and the cooling fan is pulling much more air through the radiator, thus the cooling capacity of the system is dramatically increased.

Ali hit the nail on the head. You are not overheating. I live in Florida and my 91 2.6 does exactly the same thing. When you are moving, you have the additional cooling of the moving air past your radiator. When you stop, you have less cooling. Increasing your rpm will increase your fan speed and coolant circulation. If you keep revving for a long time, or rev at high rpm, you will see your car get hotter. Your car is fine. Just make sure to flush it every year or two, and keep an eye on that temperature guage, just in case something were to fail. Good luck. Wayne Reynolds

smk_texas,
If you are very worryng about the temp., check out which type of thermostat your car is using. There should be generally 2 available- 87c and 72c (marked on the thermostat). If 87c, replace it with the 72c one and your car will be running at about 10c lower generally...
Just my experience

Also make sure you are not losing coolant inventory through your radiator cap. I replaced mine and no longer have to top off the antifreeze every week.

[Ron Johnstone]

Might be worthwhile to shine a light through the radiator at night to see if you have picked up a layer of dirt, mud, bugs, varments, etc. that could be screwing up the air flow/heat transfer. A good washing might help, although you don't seem to be in big trouble.