I've had this 69 F250(390) for only a month or so (got it from son). The temp gauge never worked so I replaced the sending unit, and the first day it pegged to boil! Weird huh? The engine has only about 30K and I replaced the Thermostat (190 degree) today. The truck ran cooler but still almost out of operating range. I nursed it home and when I stopped it was hot, but not at boil yet (unless you were to remove the cap). The radiator front was warm all over so it’s not blocked. Any ideas? I don’t if she’s been running this hot all along or what! Any ideas of what I can check now? Do these engines run hot or ...



Lonallie@cs.com
lonnie.dotson@boeing.com

 

First off the sending unit and the gauge must be compatible. An after market sending unit may not give the correct reading with a factory gauge. Hook up a direct reading gauge. They come with the sending unit, tube and gauge as an assy. Hook that up and drive and see what happens. You can also get a stick on pyrometer type temp strip and put that on the head or block and see what that reads.

 

That's something I thought about (the sending unit and gauge not being the same)..I'll try your suggestions. Thanks

Lonallie@cs.com
lonnie.dotson@boeing.com

 

My 390 with a factory sending unit and gauge always runs within the "normal" range, but even after very short trips, the engine seems unbelievably hot. I understand aluminum conducts more energy than cast iron and then dissipates it more quickly. Hence, I've always attributed it to the aluminum intake manifold. Furthermore, I've never had a problem with boil-over, even during Houston's heatwaves.

 

After rebuilding my 390, I installed a new seding unit from a chain autoparts store. It indicated a temp that was at the high end of normal - all the way up against the H. I changed the thermostat, fan clutch, went to a high volume water pump, added water wetter, checked the gauge itself with resistors like the manual tells you to, and finally got a good electric after market gauge which told me I had no problem at all. It would get up to about 195 idling in the 100 degree weather with AC on. Moral of story is to check what the actual temp with a good after market gauge.

Good luck,

Reggie

 

Thanks for the good infor guys...I agree I really don't know what temp this sending is reading. The 30+ year old gauge might not be reading the same temp that the new sending unit is... I guess I'll try just for giggles to get a reading from the radator. I figure I can get close tosee what the temp is..and then check for a fater market gauge.. thanks guys.. I feel maybe it's not really running hot just not reading right...


Lonallie@cs.com
lonnie.dotson@boeing.com