Hi Tom, I doubt a cooling system restriction is causing your problem. You'd have to drop a lot of stuff in there to block a passage. It sounds like your thermostat is stuck open, not allowing the engine to reach operating temp. A quick way to check is to block the air intake on the grille. Watch the temp closely and see if the heat output increases. As far as higher temps in the summer, if the coolant doesn't spend enough time in the radiator it can't get rid of the heat. Flushing the cooling system is a good idea regardless, but I've never seen a blockage in anything but a radiator that caused a problem. I have however, seen dozens of thermostats stick open and cause exactly the problem you've described. Good luck