2002 Impala 3.8L V6 thermostat gauge starts below cold then creeps toward red

Question

My 2002 Impala 3.8 has been running great. However, this summer the thermostat gauge stopped reading temperature right. To the point it wouldn't move even after it had been running for hours. It would just stay below 140 which is the lowest temp marker.

However, today, with a high of 21 here in Texas, it started to just creep up to the red. The deal is, when it gets to the red, it's not really that hot. I can turn my heater on full blast and have the air pass over the engine and the air is still coming out cold.

My car is telling me that my coolant level is low too, however I just checked it and it's perfectly fine.

What in the world could be going on?

Answer 1

It sounds like you have three potential problems:

1. The first problem you described sounds like you need to replace the temperature sending unit. This is important not only for your piece of mind (so you can read the correct temp on the gauge), but for your engine and fuel economy as well. Your computer could be reading the temp of this sensor and giving incorrect fuel to the engine, thinking it's hot when it's still cold. Not good.

2. The cold coming from the heater vent is telling me either you have a thermostat stuck wide open or that you have a blocked heater core (no fluid coming through). I'm pretty sure it's probably your thermostat which needs to be replaced.

3. Your coolant level sensor may be bad. Over time they can get "stuff" (sediment or impurities) which coat the sensor causing it to go bad. This is just a PITB rather than an emergency type thing. You can either get the sensor replaced or just put up with it reading wrong and check your fluid levels on a regular basis.