I have an 06 2500 Mega Cab 5.9L.

A week ago I noticed that my temperature gauge would spike to the high end f the normal range than it would come back down to around 200.

Yesterday after driving a mountain pass, it spiked to the high range of the normal range again, stayed there for awhile and then can back down to around 200.

I checked the antifreeze level and it was low. So instead of filling it, I changed out the fluid. Since then I have not been able to fill it completely with the full 7 gallons, it requires and the temp guage is still going above 200 and coming back down.

Since I bought the truck new in 07 the temp guage never went above 200 unless I was towing or hauling.

Since this has been happening, I have been empty and not towing anything.

What am I missing? What else can I check?

Thanks for your help in advance.

 

The cooling system is closed. It should just about never need additional fluid. So, where did it go?

My first thought is head gasket. But tha usuallt pressurizes the cooling system, and fluid bubbles out through the overflow.

If you have a leak and are losing fluid, you'll develope air pockets in the system. The air pockets fill with steam, steam doesn't cool well, and the temp gauge does what you describe.

A common place for a leak is the rubber hose section below the turbo.

Before spending a penny, go down to Autozone and borrow a coolant system test kit. They'll charge you $80, but you get it back when you return it.

Follow the instructions in the kit, do a thorough test, and find out what's really happening.

 

I had this same problem on my 06 I changed the thermostat and the problem went away. When the engine overheats that much I think it may just boil the coolant out of the overflow or something cause I lost alot of my coolant too. I'd put my money on a thermostat and go from there. Hope this helps.

 

That for the advice. It was a thermostat that had gone bad. Replaced it and back on the road. Thanks again.