Thanks everyone for your idea's and comments. This past weekend I didn't get much done on the truck, last minute yard work needed to get done before Fall turns to Winter here in Minnesota. But regarding the truck, a short time a go I had put a new tank heater in it ( I know most vehicles in states south of here doesn't need them). This electric tank heater warms the coolant and circulates it thru the motor and heater core so the truck starts easily in the cold weather. You do need to drain some of the coolant from the system in order to install the heater. After the installation I put more coolant back in, but I'm wondering if an air pocket or something like that formed and wouldn't allow me to put back enough coolant. However, looking at the crud and ugliness inside the radiator, I have decided to pull the radiator and flush it out which means draining the system again. I have new gaskets for the water pump and thermostat housing so I can look closer at the water pump to make sure it is OK or not. There was no noises coming from the pump when the engine was running, but there could still be an issue with it. I was thinking when the radiator is back in and it's time refill everything, I would take the thermostat housing and thermostat out, and pour the coolant in there, that would make sure the block and head would be filled up. Then top off the radiator as needed to hopefully fill the system as it should be (any thoughts here). Hope to work on the truck this week and get the issue corrected. I need to use the truck for some of these Fall chores yet - once the snow comes though, no more driving till Spring. Thanks again! Tom
