mbarr101

I've been dealing with this issue for some time now and hasn't bugged me up until this point bc my truck still needed some major things fixed first. But I finally have her up and running good so now I'm ready to see what this problem could be:
I can drive down the road with my truck for 30+ minutes at a time. The moment I come into town and have to do stop and start traffic or have to sit at idle for a little bit (after 30 min of driving) my temp gauge starts to creep up to the hot side. Normally it just slowly fluctuates around the R, M and A... but after some time driving, it makes it way to the L in the word "NORMAL". Luckily I make sure to wrap up my trips within 30ish minutes at a time but I would like to someday take this truck further down the road. What is causing this? bad radiator? I just replaced thermostat last fall. I flushed the coolant this spring... tell me what ya think-

this was today. I ran 30+ minutes out of town and it ran fine. I let the truck sit and cool down and then on my way back into town for another 30+ minutes and once I hit some red lights the temp gauge starts to move towards hot...

mbarr101

1992 f150. 5.0 v8. 115k miles.

if you want the full history click here:
https://www.f150forum.com/f10/fresh-start-260282/

sdmartin65

Fan clutch. When it's that warm moving away from a red light the clutch should be engaged and roaring.

qdeezie

+1

Hausguy

My 1989 was originally sold in Alaska and I believe that the original owner placed a large sheet of cardboard in front of the radiator to keep things running warmer. That's what turned out to be my problem anyway.

mbarr101

thanks haus- i'll check for cardboard when i get home later... anyways, it's more so that the needle goes all over. it seems like it stays within the word "NORMAL" but it will sit in the middle and then go the the 'L' and then come down to the 'R'... i wish it would just stay at the 'R' the whole time.

fltdriver

It moves down because the thermostat is opening up allowing cooler coolant to circulate into the engine, past the ECT sender, moves up because the thermostat is shut and the temperature is building up pending the therm opening again. A good coolant system flush may help, as would a new ECT sender, but I wouldn't worry to much about the fluctuation of the needle as long as it remains a constant fluctuation (within the same area of the gauge).

I agree with the clutch suggestion, try spinning your fan blade by hand. It should move then stop fairly quickly, maybe a 1/4 turn. It's easier to compare it to a properly functioning one than it is to describe exactly what it should do. It should always be replaced at the same time as the water pump, when I replaced my WP I just did the E-fan conversion, cost was about the same and I never have to deal with the clutch again. I guess if you count in the upgraded alternator then it was more but I was planning on doing that anyway so I don't count it. I really love the amount of power the E-fan freed up not to mention the extra juice I have from the alternator (I can run my AC on max, blower on high, stereo w/sub cranked up, lights on, etc.. and no dimming what so ever).

gwjohns82

What's the normal temp for the transmission? Mine averages at 204

qdeezie

I don't know what the normal temperature is, but 204 (in my opinion) is a little too warm in my opinion for an automatic transmission. Might want to consider adding a cooler in there.

fltdriver

I'm guessing that he has a newer truck anyway, but yeah 204 seems kind of high considering in these gens the trans used the radiator as part of it's cooling system and the therm is 192 from factory meaning the radiator is under that temp wise. The newer F150's had been using a 195 factory therm, so it may run slightly warmer than the 8/9 gens.