Mine runs at about the 180 mark once she's warmed up... if it's not driven for a bit, and sits when it's cold out (sub zero temps) it'll sometimes drop to 160-ish, but picks right up as soon as I start driving again...

 

I know that different people's cars run at different temperatures, but my question is why does it first go up to 210 and then as soon as it hits 210 it comes back down to 160. That's what's driving me nuts, why is it doing that? Why doesn't it just hit 160 and stop as usual???

 

No ideas?

 

I'd flush the system again and see how it looks after a week or two of driving.

 

Hi all. Just registered with this forum. Hope this idea might offer some help. I have seen this problem at work recently and found that the cooling system was not completely bled of air in the system. Some systems are difficult to bleed at times. Usually S-10 engines bleed easily by themselves without problems, but there is always an exception. Check the thermostat first. Newer vehicles have jiggle valves on the thermostats that aid in bleeding air. The new thermostat may not. I am not sure what year this jiggle valve appears. If your thermostat does not have a jiggle valve, you can drill a small hole near the edge of the thermostat to help it bleed air past as you fill coolant. Using a coolant fill funnel also helps bleeding air out. As far as your Dex-Cool concerns, here is some info. Dex-Cool was made to be more "earth friendly" than the green stuff. Now coolant is all the same basic formula, ethylene glycol. Color is used to match manufacturers color. Also, some has silicates added while others are silicate-free. Dex-cool is silicate-free. Hope all this info can be of some help.

 

It's your t stat opening and getting stuck open. I would change the coolant temp sensor and engine temp sensor. Got an OEM t-stat right? It's not upside down?

I changed them on my Ranger. It would warm up then the needle would go all the way to a colder temp. Even with a 3/4 blocked radiator and the clutch fan removed. The heater blower motor is weak but this is good heat in the cab.