Quote:

Originally Posted by Bobby Davis

I'll be going down the highway and it'll be fine but as soon as.i get home it'll for lack for better words start boiling. And the oil pressure will be fine then for no reason that I can tell.just start slowly dropping. And it'll stay low for a while the slowly come back.

This boiling you talk about, is this after you shut the motor off? And does it push coolant out of the overflow?
If that is the case, I would replace the radiator cap. It is a pressure relief device set around 15psi? and if its weak that can happen.
FWIW, in my experience, (I have had 2 vehicles with this problem) a stopped up radiator, (inside corrosion) would idle ok, but overheat on the highway or under a load.
Corvettes are famous for picking up trash and blocking air flow, heck, some call them a road sweeper for that reason. But when that happens (trash blocking air flow) they usually overheat both at idle and highway speeds.

 

right water pump? 90 will be different from newer trucks. newer ones have serpentine, back of belt runs pump opposite way from older Vbelt pumps so impeller blades curve opposite way.

 

Very correct on pump directions but 90 was a vbelt and LA water pump...even if he was able to put his vbelt pulley on the magnum pump the snouts are 3" longer on the LA pump and the pulley wouldn't line up....been there done that