# Slightly overheating



## Airkewld38 (Oct 29, 2021)

So, my W8 is having a weird issue with the engine temp. As it sits and idles it's fine. But if I drive it on the highway the temp goes up just above the 190 and sits there. Doesn't change really how hard I drive it, and the heater had no effect on the temp. So does this sound like a failed thermostat to anyone else? The coolant is full, and it's recently changed last summer.


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## Thanks_a_Lottman (12 mo ago)

i delt with a stuck open thermostat during the cold Nebraska winter 🥶 Are you engine cooling fans running higher than normal? check engine lights? You may have a stuck closed thermostat or a poor performing one to where its not opening all the way? It is a MAP controlled thermostat (ECM input/output) by 2 coolant temp sensors, 1 at the top radiator hose and another behind and underneath the throttle body. i would check to see if these are acting up first. the front sensor may not be reading correctly and the ECM is only picking up the engine outlet temp? this is a cheaper/easier fix. But if it ends up being the thermostat, it may seem like a big task but once you get started, its fairly easily. Its below the intake plenum and runner. If you do change the thermostat and go with the cheaper aftermarket one, you will need to cut the OE harness plug that goes to the thermostat and splice in some extra wire to reach the new thermostat's plug. If you have basic mekenick skills and tools, you should be just fine. id give this a 4 out of 10 on difficulty. just dont drop anything down into the intake runners of the heads 😋 good luck


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## Butcher (Jan 31, 2001)

190F is not overheating.


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## seawall90 (Nov 27, 2021)

If it's steady, it just may be a calibration issue of the gauge itself. How does the engine smell and feel? just after stopping, can you leave your hand on the manifold, should be able to. If it's overheating you'll smell that coolant.


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## Phaeton4me (Jul 24, 2017)

If the coolant fans are running in high all the time it is likely to be thermostat. When idling the airflow is adequate to cool engine with no load. Need to have a Vag-Com scan program if you own this car. I own a W8 and 2 W12s. The thermostat is the most common issue.


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## Butcher (Jan 31, 2001)

In 1987, I went to a BMW E32 class. They mentioned one of the 'problems' that customers have is the fact the coolant temperature gauges fluctuates while driving. Anyone that knows about cars just stays 'DUH'. Well, duh does not work when talking to clients. 

So the factory engineers designed the gauge to read in the middle. It satisfies the driver. The fact is, nothing changed. The engine is still fluctuating with the temperatures. Problem solved. If you ask any BMW owner where their temperature gauges runs at, it is always exactly in the middle. It slowly goes to the middle on a cold start and will never go higher unless there is a dramatic temperature change. Then there is a large swing from the middle to the red.

I really believe most manufacturers are this way. I never use factory gauges to find out the facts. Well, maybe the fuel gauge, they are pretty accurate.


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## Airkewld38 (Oct 29, 2021)

I've used the Vag to check the temp though. It went above 190, up around 200-205, but wouldn't go much further. I'm boiling this down to an electrical issue, where I'm getting a wrong signal from somewhere. It's got a slew of codes that I'm still chasing my tail.


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## Butcher (Jan 31, 2001)

Are you just looking for a problem or is there an actual problem? It seems to be you are using your logic and telling yourself there is something wrong. I used to do that until I grasp that the Germans have their logic and you need to adjust your way of thinking. A lot easier than changing a German engineer way of thought.

If there is enough capacity of the cooling system, the system could keep it at a constant temperature if you were at the North Pole or Death Valley. 

I had a 4Runner that was that good with the cooling system. 124F with the A/C on full blast going up some of the passes in the area, and the temperature was rock steady.


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