Hot Mess

Hello all,
Have been fighting overheating since last summer.
Did a prestone flush and power washer purge and suspect my fan clutch is failed as is can be stopped w cardboard when cold & hot. When temp gauge is almost to Hot, it spins like it's on brgs when eng is shut off.
Any suggestions as to a good or bad fan clutch? I'm suspecting I may be needing a radiator as it's original '89 G54B unit. Got a fair amount of flaky crap out but still running warm. Changed T stat too.
I welcome any suggestions. Thanks to all.

what does the temperature look like on the highway, still climbing?

it sounds like you need a new fan clutch anyways. but it shouldnt continue to climb in temp while you are moving at highway speeds, if you have a copper radiator i would suggest getting that rodded and flushed if its otherwise in good condition. check the fins are not all bent closed or full of bugs. you could also be due a new water pump , but see how it goes before throwing a whole parts list at it

tortron is right hold up on replacing the radiator especially if it's an original factory brass unit they can be repaired or have a new core soldered in ~ try testing the sending unit in a pan of cold to increasingly hot water (maybe do it in the engine compartment with alligator clip ended ground wire see what the dash gage reads with the pan of boiling water)..?

My truck has two coolant sensors next to each other one for coolant temp to the dash gage & one for the ECM to control the engine (emissions?) Maybe your engine is not really over heating maybe the sensing unit is bad or even a bad gage..?

Anyway get a new fan clutch about $40.00 and keep posting your progress

Good Luck

Thanks Men! Further troubleshooting in process. Responses appreciated.