Let me begin first by saying that I'm the current owner of 20Screw01's truck. For anyone who doesn't know, it's an '01 Supercrew with a '00 L engine. The truck has always ran near flawlessly, still does, but for the past couple months I've had an intermittent issue. When I jump in the truck and start it up everything is fine 100% of the time. The problem arises after the engine has reached operating temperature. Every now and then (much more frequently lately) a short time after the truck has warmed up I will look down and notice the temp gauge is maxed out and the red engine coolant light comes on. I immediately let off the gas and begin to coast. I turn the HVAC to panel and crank the heat full blast. After a little while (It varies) the light will go out and the temperature will return to normal and it will not happen again for the duration of the trip. However, turning the truck off and then back on for the next trip will "reset" the possibility of this happening again. Yesterday I replaced the thermostat (Had a 185*, I put in a 180*) and filled the coolant for both the engine/radiator and the intercooler. (Engine coolant was about a gallon low) The truck does not leak any fluids whatsoever, the coolant does not look milky, and I'm still consistently seeing 8 psi on my Autometer Ultra Lite boost gauge. I'm pretty worried about my pride and joy, any help would be appreciated.

 

If you are not leaking water then it can only go to a few places. Crankcase or cylinder head. Either one is bad and requires immediate attention. the coolant being low would explain the gauge pegging out, but where is the water going? Are you burning it? Check exhaust for excessive water vapor and check the oil to see if it's milky.