Thanks Stumpmi. I'm about to flush it and see what happens. You know I thought maybe the heads or intake gaskets but its not consistent

 

YOUR VERY WELCOME !

LIKE I SAID ALSO KEEP IN MIND:

TO BE SURE TO GET ALL THE AIR OUT OF THE SYSTEM.....

ID BE CURIOUS TO HEAR IF IT HELPED.....GOOD LUCK !

 

I had an issue on a 3100 when the head gasket failed, it sent compression gases into the coolant system. The gases (air pocket) is hotter then coolant and caused my temp gauge to spike until the T-Stat opened (while the temp gauge was pegged, I had no heat from the blower, once the t-stat opened, heat from the blower again).

Not saying it is, but it might be a head gasket issue. Things to check:
- Make sure the coolant system has been properly bled of air pockets
- Change T-Stat
- Use a scan tool and see if the PCM temp reading matches what's on the instrument cluster (verifies you don't have a cluster problem).
- If a temp sensor fails, typically you don't see a natural response reading on your gauge (temp rises as the car warms up and goes down when the T-Stat opens).
- Get a radiator test tool (loan a tool from the parts store), pressurize the system and check for coolant leaks of or loss of pressure on the coolant system.

If nothing points to the cause of the problem, you might be looking at a failed head gasket.

 

+1 to the failed head gasket. I have to do them on a friend's 3.5 this weekend. Will idle at 200* all day long. As soon as you start driving temperature comes way up. As well as some other tell tale signs.

 

Just gonna throw it out there, but my '03 was doing this when I got it, was the stupid plastic intake gaskets!! What year is yours? This usually happened within the first 15-20 minutes though.