He has a V6, going by his post history.
Hmm... Well, you are most likely going to have one of five issues.
1.) Thermostat could be faulty. Though I've never had one that fixes itself. Usually once they go bad, they stick that way (most are designed to fail in the open position to prevent overheating damage). But I'm sure it happens.
2.) You could have some big air pockets in your cooling system. This could show a false reading of the coolant temp gauge, and explain why you had no heat. Kind of unlikely for both of those symptoms at the same time.. but possible. Did you hear any hissing or gurgling sounds when you got home and turned it off?
3.) Your coolant temperature sensor is on it's way out, giving incorrect readings on the gauge.
4.) Cooling fans are not operating as they should, causing overheating after sitting in traffic for a short while. I had a situation where the fan wouldn't come on in traffic but once air started pushing through the blades (or carefully giving a quick light push on the fan blade) they would then kick on with their own power. But, my logic tells me if your cooling fans weren't working correctly and it was indeed overheating, you should of had hell coming out of those vents.
5.) Possessed dash cluster.
Keep note of whether the temp gauge stays at that quarter mark. It might seem "good" but something is wrong if it is not staying near the middle. If the thermostat is now stuck open, eventually you will get a service engine soon light because the coolant stays too cool and the computer will see that.
Our engines are designed to run best at the factory set temperature. Cooler is not always better. Leave it with a stuck open thermostat and you will start noticing decreased gas mileage, decreased performance, no or very little heat in the winter, and your transmission will prematurely wear because 1, it needs to be at a specific temperature before it will go into overdrive (which puts less stress on the tranny, less rpms from the engine, therefore better gas mileage) and 2, cold fluid will not give you the smoothest shifts.
One way to test your thermostat without opening the hood.. start your car on a cool night. Let it warm up. Turn the heat on full blast.. observe how hot the heat is. Now, get on the highway and go for a 20 minute drive at a consistent 60+ mph. If your heat gradually gets cooler and/or you notice your temp gauge drop quite a bit... your thermostat is bad.
Sorry for the novel... I like to be detailed!
miles as of 04/23/10
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