When I first bought my car it took a notably long time to warm up. My friend said his 90 LS was the same way, so I thought nothing of it. Once it reaches operating temperature it will stay there... for the most part.

In the city it's fine, but during extended periods of engine braking on the freeway my temperature gauge will drop from full operating temp down to the cold mark, if not past it. For example, if there's a stretch of freeway that has a slight downhill grade for a mile, my temperature needle will move 1/4 or more of the way down to the cold mark. The decrease in temperature is more notable if I stay in 4th gear, opposed to 5th.

This leads me to the idea that the thermostat is broken, not creating a good seal, allowing cold coolant to flow at all times. It doesn't sound like it's normal, but I wanted to see what all the DA owners have to say.

 

It could indeed be a stuck thermostat. Try replacing it and see what happens. It's not an expensive or difficult job.

 

My DC did this exact same thing, and it was indeed the thermostat... super easy fix, about a half hour to do the t-stat. then another half hour to do the coolant....

 

Yup, that was it. If you hold the old t-stat up to the sky, you can see daylight around the rubber seal in the middle. I'm sure that, along with 32psi in my tires instead of 22-25psi, will get me better mileage. Thanks for the input.

 

i think the way they are designed now is to stay open when the finally go out, that helps to avoid overheating.