I've got a 92 F150 with a 5L that won't get warm. Temp gauge hovers just barely over lower "normal" line at highway speed. Radiator hoses don't seem to pressurize fully. Smell coolant outside truck, but can find no sign of leakage and radiator is always full. Have replaced radiator cap and am about to replace thermostat this weekend. Any thoughts on what else I should check while I've got it apart? Thanks

 

Stuck open thermostat would be a first guess. I'd pull it, and then watch to see if it cycles in a pot of water brought to a boil.

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