89 truck. New toyota radiator and t-stat. truck will idle all day long at normal temp. Takes about twenty min to start creeping up in temp when driving. engine is new to the truck. checked head gaskets and we have nothing sticking out the passenger side. stumped???? open to ideas. This is a friends truck that i am trying to help him figure out. thanks Kevin

 

A list if things to check, fan clutch, radiator shroud, water pump may not circulate, clogged passages in engine or hoses. How hot does it get?

 

A list if things to check, fan clutch, radiator shroud, water pump may not circulate, clogged passages in engine or hoses. How hot does it get? A lean running engine also can overheat.

 

fan clutch is operating good. radiator shroud is all in tack. thinking water pump my self as that is our next thing to check. It will continue to creep all the way to hot. but as i have said will idle all day. might do a full thottle run down the road and pull the plugs. then i can rule out being to lean. i am leaning towards WP as bottom of new radiator is staying cool just like the old did.

 

Did you burp the coolant system and add coolant? Are you sure you got all the air out of the system?

 

we filled the system with the funnel that fits in a gutted radiator cap. believe we might try a different way this evening. hopefully that is all it is.

 

Park the truck with the front up hill & fill while the engine is running, allowing the system to burp itself. That's the only way to ensure you get all the air out.