I've already had the broken housing issue 2 years ago, this is the thermostat that came with the new housing.

Recently noticed the car is not warming up as quickly as it should, but not bad enough to throw a P0117 code yet. Sometimes warms up fine. I've been watching the coolant temp on my scan tool, on the highway going 70-75 mph on flat road, my coolant temp goes up to 200F. It's 35 F outside. Shouldn't this be able to hold the engine temp at 195 on the dot with that much cooling air? At what temperature do these cars generally hold the temperature?

The FSM is vague about the regulating temp.. says "thermostat begins to open at 88°C - 92°C (190°F - 198°F) and is fully open at 102°C
(216°F)". Does that mean my tstat will allow the temperature to get up to 216F?

Thanks, and Happy New Year!
-Michael

Michael-

All modern cars have enough capacity built into them that the cooling systems can get rid of heat faster than the engine can produce it under almost any condition. Just as it's obvious that and engine should not be allowed to run too hot, it can be almost as bad to run one 'too cool' despite what the hotrodder set thinks.

The OEM will determine an optimum running temp for an engine and specify a thermostat setting that will attempt to keep the engine coolant at that given point, plus or minus a few degrees. Since auto thermostats are simple old school mechanical devices with known manufacturing +/- tolerances, the actual opening temps can seem unacceptably inaccurate in today's electronic digital age where things can easily be measured to the 5th decimal place.

Sounds like your particular thermostat and cooling system likes stabilizing itself at around 200*F. Below that the thermostat will start to close to increase the temp and above that will open wider to cool things back towards 200*. It's possible that if you were towing a trailer across the desert in summer the system might run out of reserve capacity and even with the thermostat wide open 216* might be reached, but that doesn't constitute anything being worong or overheating.

I think if you turn off your scan tool, most of these problems will go away.

Yes, I agree completely that a normal operating cooling system can range from 190-210 under perfectly average conditions. My Cadillac's radiator fan would not even switch on until something like 220F. My ulterior motive for asking the regulating temp is relating to light pinging I get at 1750 rpm whenever the temperature is over 195 F. Most definitely temperature related, engine is silent until over 195. When it stays cool it's quiet (i.e. if I run the a/c when it's cold out, the rad fan runs and keeps the temps right at 195). Had a dealer re-flash for "pinging on light throttle" and have done several courses of that BG44k injector treatment, searched for air leaks, etc, no difference from any of those. Fuel trims all looks fine from the diags. Hate to throw a MAF sensor or O2 sensors at it if there's nothing pointing to those.

I highly doubt it's detonation/pinging.

Well, with all due respect, I've heard enough engines ping in my life to know what pinging sounds like. This isn't heavy detonation, just a light ping or 'spark knock.' I'm not sure what else would make a "popcorn poping" noise in an engine... But I'm certainly interested to hear if you think it's something else. I had considered it might be the VVT, since it is very RPM specific, but that does not explain it's occurrence only when the engine gets warmer than normal. What else do you think it might be?

There's a hundred different rattly clicky sounds that seem similar to detonation- but aren't. My cars make at least a half dozen of them.

The condition you mention- consistent, steady, moderate RPM- is not usually conducive to detonation. It would be difficult to explain why the knock sensor doesn't hear and correct the condition.

Also consider that there is a response time inertia that causes the temp to vary. Consider you are driving quick and moving well at light load, but suddenly slow down behind a truck, on a hot day, up hill. While cruising the thermostat would regulate to a reasonably closed position due to light heat load and good cooling. Now the water temp will increase and the thermostat has to respond to the increased heat load and open up to cool the water down.
Now if you get back to the highway, the thermostat would be well open and the increased cooling would lower the water temp faster than the thermostat would respond. These heated wax thermostats have a 2-3 minute response time.

I guess if they used a electronic controlled valve and CPU control, they could have faster and tighter control of temperature, but I am happy if they do not add an additional 100 components that could fail...