2004 GMC Sierra 2500hd

[slamont]

I have 2004 Sierra over 300k started it to warm it up engine coolant hot came on. When to start it to day and just turned the key and in the display engine coolant hot. I change the coolant this summer. Not sure what this is about any thoughts?

[Wicked Mickey]

I'm assuming you're problem has resolved itself now?

 

The cooling system may have a little air trapped in it. This will eventually migrate to the top of the radiator and be purged to the overflow bottle when it cools. I call this thermocycling. You'll have to top of the over flow bottle a couple times to make sure your level is correct.

 

You may also need to replace your radiator cap. It may not be maintaining pressure