My temp guage quits and goes to 0 then the engine fans come on. I have checked and there is 5 volts going to the temp sensor. I have also checked the resistance of the sensor the ohms go down as temp goes up and vise versa. What else can I check?

 

Coolant Level!
Verify that the system is completely topped-off with coolant and that there isn't an air leak preventing the Overflow Tank to replenish the level in the system.
There are a couple of coolant air-bleed ports.
Plus ... the Overflow Tank design is very poor on the 04. There is a gooseneck that is supposed to be filled with fluid and gets "Air Bound". You have to undo the fasteners on the overflow tank. Hold some folded-over paper towels on the filler neck so it dont leak ... and invert the Overflow tank to get the air out of the gooseneck and let fluid flow into the overflow hose back to the filler neck and radiator cap connection.

 

Yes that had me wondering when I bought this car it did'nt have a overflojug it just had a bolt in the end of the hose with a clamp on it. This problem started ever since I put a overflojug on it. So do you think I am getting air pockets in my motor?

 

How do I check this or where do I blead the air out?

 

This happened to my Monte two years ago. It ended up being the thermostat was stuck open and not letting the engine get up to temp. The computer monitors the engine temp and when it senses that the temp is not getting up to where it is suppose to then it goes into protect mode and turns on the fans to protect against over heating. It also quits sending a signal to the gauge because it is not sure of the true temp of the motor. This is your indication that something is not right. Just replace the thermostat and it should fix the problem. I'll bet you started seeing the problem when the weather started getting cooler. The warm summer months with the A/C running keeps the engine warm enough that you don't see a problem. Now that the weather is cooler your engine doesn't run warm enough to break the threshold temp to satisfy the computer.

 

Yes it was the thermostat and it did start when the weather got cold.