Car running cold

[97GreenGTP]

I have a 97 GTP with 240,000 miles. Until last couple of weeks, the car temp gauge would always read around 160 (at mark in middle of 100 and 210) at highway speeds and in cold weather. In stop and go traffic during, it would reach 210 or sometimes higher.

However, lately, the temp gauge wont reach 160. It stays in the middle of 100 and 160 (mark between 100 and 210). In stop and go traffic, it would reach around 160.

Can anyone shed some light on why this might be happening? Is the thermostat staying open all the time to let coolant flow through the engine and cool it? If its the thermostat, how much work is it to replace it? Are there any disadvantages of engine running cold?

Thanks in advance.

[grandprixgtx00]

change the Tstat. if you remove the plastic engine cover, you will see where the upper hose goes into the engine...there is a metal cover that is over the t-stat. very easy to change. if the radiator hasnt been flushed in a while, might be a good time to do that.

[tblake]

Unless you have a 160 degree stat installed. 160 is WAY too cold for a 195 stat (if your at the stock temp).

[97GreenGTP]

Here is what I found out after talking to a few people:

Since the care is heating up in normal time (not taking too long) and hot air is hot enough, chances are that the thermostat is ok but the temperature sending unit is bad. If the thermostat is bad and stays open, the car should take a long time to heat. So this week, I am changing the thermostat and the temperature sending unit. I believe the sending unit is just below where thermostat is mounted. Parts are cheap in this case so while I am doing one, I might as well change both.