imflyn

iTrader: (2)

The last few days my car has started running cold. It's a 98 so the temp gauge actually works. Normally it would run about 175 - 180 but all the sudden it only warms up to 160 - 165. So today I drove around awhile highway and stoplights and no change. I let it idle in a parking lot and it warmed up to about 210, the fans kicked on and it cooled down to about 185. Then when I started driving the temp fell back to about 165. I'm guessing the thermostat is stuck partially open. The upper and lower hoses are warm even though the temp stays low. Coolant level is perfect. Either this weekend or next I'll change the t-stat. Just wondering if anyone has any experience with this or other ideas?

Tuffguy610

iTrader: (2)

Hey there. Every GM I have had except my LS1 has had a problem similar to what you are describing. Usually what happens is the thermostat fails in the open position, making the coolant constantly flow through the radiator (when it shouldn't because the engine needs to warm up). Therefore, the engine never truely gets warm. You might have heat since the engine heats up while idling because there is no airflow through the radiator. There are a few ways to figure out if it is the thermostat.
1. Start your car and drive it within one minute of starting it. Don't give the engine a chance to warm up while car is stationary and no air is flowing through the engine bay.
2. Turn on your heat while driving, if the air in the vents isnt becoming warm within ten minutes, suspect the thermostat.
3. If you have an automatic transmission, try to drive over 50 mph to see if the torque converter locks up. If it does not, you probably need a thermostat because the engine isnt hitting "closed loop" mode.

In any case, I would probably replace the thermostat. My 92' Camaro suddently started having no heat and no converter lock up and a new T-stat fixed it right up. The same happened to my 86' Cutlass Ciera and my 88' Pontiac 6000, the thermostat fixed them too. It isnt that hard of a job, and it seems to me that it probably needs to be changed based on your description. Good luck.

imflyn

iTrader: (2)

Thanks for the input. It is going into closed loop within about 5 minutes (tc locks up) and I seem to be getting heat like normal maybe a minute or two later. Hard to tell since it's been so cold lately. I drive home from work every morning and its always below freezing. The engine just doens't warm up "all the way" Maybe it's stuck in a sort of middle position. Being the cheapest and simplest I'll start with the t-stat.
thanks

imflyn

iTrader: (2)

Replaced the t-stat this weekend and everything is back to normal. woohoo!

Tuffguy610

iTrader: (2)

There ya go!!

tripps

iTrader: (7)

I had a similar problem, except that the T-stat wouldn't close..Thats a scary situation when you see your temp gauge jump up to 260 real fast. Glad you got it fixed.