Engine Temp. High?

[Mr. Detail]

Happy Monday guys!
Here is my latest quandry and I don't know what to do.
I am getting a message in the lower left corner of my instrument panel stating "ENGINE TEMP HIGH".
The needle on the temperature gauge went all the way to the right as though it was overheating but nothing seemed to be
wrong with the engine itself. No smoke, the coolant is at the right level. Also i do not receive a "check engine" light which would help me with a code. Any thoughts?

[ignatz]

Years back, my 2001 V70's temperature gauge started rising in traffic. It cooled off while driving home and I found some critter put a nut in my cooling fan and made it lock up. I removed the nut and all was well again. Make sure your cooling fan spins freely.

[erikv11]

Another possibility is an issue with the ECT (Engine Coolant Temp) sensor. Did the needle rise slowly or just abruptly peg to the right? Also I am unsure from your post: Is the needle stuck there or reads lower after the engine has been off for a while?

[Mr. Detail]

OK, the car has been sitting in the driveway most of the day. It is 8:40pm EDT and it is a bit chilly. I just went out and started the car and watched the temperature needle immediately pin to the right very fast and then it took about 30 seconds to slowly return all the way down to the cold side.
After shutting the car off, I could hear the fan running under the hood. I opened the hood and the fan was blowing air just fine and the fan stayed on for at least 5 minutes which seems odd since the car was only running for maybe 2 minutes. Does this help at all?

[erikv11]

Yes! Those symptoms all points to a failed ECT sensor. The car isn't hot, rather the sensor is sending faulty information that it is, reflected in the gauge behavior and the fans turning on the cool it off. Info from he ECT is also used by the ECM to adjust the air:fuel ratio so the car may be running poorly or starting hard.

For an 02 V70 NA the ECT is pretty simple to replace, it is at the base of the thermostat housing. You can do some tests on the old one like check resistance at different temperatures but it sounds like the ECT is bad. I am however surprised there is no CEL, I'd expect that with a bad ECT. Maybe it will show soon. ALso you should check the wiring to the ECT, on both the harness side and the sensor side.

I'd grab one from the junkyard to test by swapping it in or just replace it. If you buy a new one I'm not sure about the best brand to get for an 02. For most years the aftermarket ECTs are notoriously problematic, it is crucial to get Volvo or equivalent.

EDIT: here is a decent informative video

[Mr. Detail]

erikv1, thanks so much for your response and the good video. Actually, this is also weird, the "check engine" light did come on last night when I started the car but when I plugged in my cheap code reader it said "no codes". Then the light goes out. Very sporatic.

[Mr. Detail]

erikv11, can I still drive the car to work in the present condition? I really need this car but do not want to cause more problems if I drive it say 12 miles.

[abscate]

Drive it with heightened awareness. You no longer have a warning system for coolant loss, so if you had a hose break you would ruin your engine. If it is running smoothly and starting easily, the ECU is using the default start map which will run fine. On VW if the ECU doesn’t like the ECT sensor readings it adjusts the mixture based on time from start. I think Volvo does the same.

When you run into problems on the default map is on multiple stop and go hot starts

[vtl]

When you run into problems on the default map is on multiple stop and go hot starts

Out of curiosity, why? The default map supplies more fuel to prevent frying the H2OS until it heats up to the working temperature, is it starting interfering with something once the engine is hot?

[abscate]

Since it is metering fuel based on time from start it will deliver cold start fuel to hot engine, which will flood it.

Cold start fuel is about 3x mote than warm engine injection, at idle