Still having Cooling issues, is my ship sinking?
Ok so starting out I began seeing my gauge go from normal operating temp up to 3/4 or all the way to red VERY quickly while under a load or running at speeds above 60mph. The fan is engaging and as soon as I get back to idle or slow down to 50 the coolant gauge returns to normal operating temp just as quickly as it rose. I have looked all over the coolant system for leaks and found none, and had no coolant backing up over the degas bottle so I assumed a Coolant Sensor or a T Stat. Replaced both of those, refilled the system and the truck seemed to be back to normal fora few days....That is until I hooked to our dump trailer and hauled it down the road! Same symptoms as before but now I have no heat coming from the heater. There is no noticeable loss of power and still no visible sign of any leaks. Even when I get to a stop I always check the degas bottle to see if there is any coolant boiling or steam and its just as flat and still as when its cold(until I let the pressure out). Truck is a box stock 03 6.0 with 231k on it (no ford gold, has had ELC in it since 150k) Truck is used mainly just as a to/from work truck but pulls a dump trailer 1 to 2 times a month with gross weight of truck/trailer never over 7 tons.