I have an 06 3500 drw, auto. afe intake, 5"exhaust. I dont know about any programs because I bought it used. 90k miles. This problem has been intermitent but getting more often, almost daily now. The heater will blow hot air and then all of a sudden change to cold and the temp gauge on the dash will climb rapidly almost to the red. After a while I will start to get heat again and then temp gauge will quickly come back down (in about 10seconds) to 200. The truck also seems to be running a little over 200 degrees and my memory is it used to always be at or just below 200. I think I may have an air lock in the coolant somewhere and should bleed it. Any chance the increased running temp is a headgasket issue? All of these temps are while running empty and not pulling a load.

 

I'd agree with looking into "air" getting into your cooling system... maybe thermostat issue too.

 

I'd start with the easy stuff first......check the t-stat and replace if necessary and then check for any air in the system. Have you had the system open lately to allow air to enter it?

If it was a head gasket issue you'd be losing water......water in oil and vice versa.

 

Thanks for the replies. Just got home from work and on the way home things got even wackier. The temp stayed about 1/8" above 200 the whole trip, but the last few miles are uphill and it started getting hotter close to the red but never in it. At the same time the torque converter was not locking up, the rpms would drop to 700 or so whenever I let off the gas (traveling speed around 45mph). In the driveway I parked it and it went into high idle. I reved it and the engine would sputter as the rpms decreased and it would climb back to high idle again. Does the transmission have a different mode it switches to if the engine is overheating?

 

Mine will go into a de-fuel mode in that type of situation. It protects to transmission from being damaged.

 

A small leak in the head gasket is all it takes to cause that issue. I know because I've dealt with enough of those 5.7 Olds diesel engines, plus my dads 6.2 here a few years ago. New head gaskets and it solved the problem.

 

well I had a few minutes to look and my coolant overflow tank is completely empty. I cant find any signs of leaks anywhere. the oil is black, I dont see any coolant in it. I guess it could still be the head gasket and I am just blowing coolant out the cylinder.