2001 F150 Running Hot/overheating- Need troubleshooting help

[akfodysvn]

I've noticed on a few occasions that my 5.4 truck was starting to run hot in this heat with the AC on. Turn off AC and it seems to fix it initially. Only happened 2 times that way and I just shut off the AC and went on my way.

The AC has always worked shitty at idle/low speed but blows cold when cruising on the hwy. I've towed no problems previously.

Went to pick up my boat today an hr away (5k lbs) and on the way there it crept up 3/4 or slightly higher on the temp gauge but went back down once I started going 80 on the HWY. No issues even with AC on.

Towing the boat home it was running pretty hot but not overheating. I kept the AC off and it would intermittently get better but then go right back up. The it seemed to run slightly better temps while going 75mph instead of 65 so I hauled ass home. No real correlation between running the AC or not.

One block from my house my temp gauge shot all the way to hot along with the oil warning light. The indicator looks like "oil temp" but I dont know why that would be the case. Oil pressure remained good throughout. I made it home and just got the boat put away and truck cooled off.


-Coolant looks good
-No leaks noticeable
-Nothing blocking airflow to the radiator as I just rinsed that area to ensure it was getting good airflow.

I'm thinking possible fan clutch and reading those water pump impellers erode and don't move much water. Thermostat would be another easy part to throw at it but I'm not wanting to just throw a bunch of shit at it.

Possible causes...
fan clutch (fan spins freely by hand)
T-stat
water pump

[sig239]

Fan clutch would be my first, it should have some resistance spinning it, higher speed more air moving across the radiator.

[garycrist]

Time for electric fans.

[Lone Star Performance]

Have your pressure tested the radiator cap?

[akfodysvn]

I have not.

I noticed the serpentine belt is not touching the idler pulley. Not the tensioner pulley but the idler pulley. Seems weird to me that it doesnt touch the pulley.

Top left pulley


I drove the truck home with the ac on in 95° heat with no issues.

[GeorgeG.]

is your belt routed properly?

let me rephrase that...if your engine is running it seems like your belt is not routed properly. Could you potentially be spinning the water pump backwards?

[shumpertdavid]

Belt looks to be routed correctly you can physically see the belt isn't touching, make sure the pulley hasn't seized. It doesn't make a lot of contact, it's there to keep the belt lightly tensioned between the compressor and alternator.

[akfodysvn]

Thanks for the feedback. It's routed correctly as per the ford diagram. I just had no idea what that pulley is for...if it doesn't make contact.

I went ahead and replaced the t-stat just to see. If the problem comes back I'll do the fan clutch and water pump for about $200. It's been a weird problem to try and track down to be honest. I can't duplicate it regardless so the tstat was cheap and easy attempt.

[soap]

Fan clutch would be my first, it should have some resistance spinning it, higher speed more air moving across the radiator.

Yup.