Soooo for the past two days my 04's fan has been kicking on for no apparent reason. She wasn't overheating but the fan would kick on while my temp needle was just below the 1/2 way point between C & H (which is where she usually stays)

Well, driving home today the needle started to creep up towards H but I was pulling into my neighborhood so I got her shut off quickly. My first thought was the thermostat so I took my girl's car to autozone, bought a new one and installed it.

I turned the car on and it was idling fine and the temp got up to the usual spot (1/2 way) for about 5mins, then the fan kicked on, I went for a little spin and the temp started to rise again and the heater is blowing cold air.

Would my car still overheat if there is air in the system? What else should I be looking at?

Thanks in advance.
Chris

 

Also, the heater will blow hot if I'm driving over 20mph

 

Rule 1: air in the system.
Rule 2: yep it's air.

Over 90% of the time, refer to Rule #1

 

Yup, but the thermostat does go bad from time to time. Rule #1 and #2 10x times before moving to 3

 

Is your coolant overflow tank filled up and won't come back to normal level even when the engine's cooled down? If yes, then you got a bad radiator cap. This is overlooked sometimes.

You can confirm it's a bad rad cap by squeezing the rad cap spring. If the spring is stiff, you chuck it in the trash bin and get a new one. The car overheats because the coolant is discharged towards the overflow tank and it's not being sucked back in to the radiator due to the messed up rad cap. This causes massive massive air bubbles.

Change your rad cap as you flush out the air bubbles.

 

Go to a shop and get a coolant flush. That should do it all. Two birds one stone

 

I think most of the air is out of the system and I'll continue to bleed it off periodically but temps are now back to normal...

My problem now is the radiator fan turning on and not turning off until the car is turned off. Even at night and cruising in 6th at 45mph, I can hear the fan going... I think I have a bad relay but where is it??

 

That's because your engine is really heating up. Have you tried changing the rad cap yet? You bleed the air out but it will come back again. For explanation, see my previous post.

Check for bubbles again, once the engine cools down. I'm pretty sure you got bubbles again in the system.

 

Sounds like an air pocket. Just because the needle isn't high does not mean the vehicle is running at normal temp. Please take it to someone that can bleed the system before you really over heat it.