So last month while towing the camper up I-70(6% grade) and the oil temperature got up to 258F after I had pulled over, turned the floor heat on etc..(it was 94F outside and camper weighs 9k roughly). The water gauge on the dash then climbed to just under read line and then cooled off. Since then I've paid a lot more attention to the engine oil temperature. Other info while towing:
Speed: 40mph
RPM: 2400
Foot: 1/2 to 2/3 throttle
TC: locked in 3rd
boost: 16psi
tune: hydra stock tune
EGT: 1200
Transmission temp: 210 on TP, 200 on test port gauge( have the 6.0 cooler)
Fuel pressure: 58psi(67 normal driving)

Maintenance done last summer:
-New degas bottle
-new cap
-oil cooler re sealed by mechanic( he noted that one of the holes was completely clogged by a silicone looking material and noted that it was so corroded he didn't want to polish it for fear of putting a hole in it)

PO maintenance:
- Water pump and thermostat at 233k and new coolant( No idea if its a 192 or 203 thermostat)

Current mileage is 286k

So driving home from work today with the AC on the EOT got up to 208 on the way home. As soon as I got into the driveway, I hopped out and grabbed an IR thermometer(Milwaukee brand). I measured 5 different spots on the radiator through the fan shroud and all of the readings were around 168. I couldn't remember where the EOT sensor was so I pointed the IR gun at the HPOP reservoir and it said 198. I believe the coolant system is holding pressure because the morning after driving it, the upper and lower radiator hoses were cavitated and released when I unscrewed the degas bottle cap. In other words, it held pressure for roughly 12 hours after shutting down if that means anything. I added coolant two weeks ago and it's still at the full line when cold.

Misc
-EGT gauge only measures the drivers side bank. I just re ringed the injectors, finding two with crusty rings. Passes contribution test with highest perdel being 2.4 on #8 and #4. #1 and #5 are less than 1.
-Hutch mod is not done yet, though I do have the parts sitting in the garage. That will get done hopefully this fall when/if the kids go back to school.Even just passed emissions with it's best opacity yet.

I would really appreciate any suggestions in how to troubleshoot this.

 

258f EOT too high for sure.

208f EOT good for all day long..?

 

The thing I don't know is if the wide discrepancy between the coolant temperature and the oil temperature is normal. 168 at the radiator and 193 at the hpop reservoir. Is that normal?

 

EOT is engine oil, right? Not engine operating temp.
I'm not so sure that 258 for oil temp is too hot. Remember, your oil cooler cools oil and it wouldn't be cooling much from 208. Just my thoughts and I'll wait for someone who really knows to chime in.

 

At a glance, this sounds like a bad fan clutch.

You should hear the fan engage while pulling a grade like that. It’s LOUD. Even at highway speed.

When my clutch failed, truck would get hot like you described when on long grades. The first time was pulling I-17 from Phoenix to Flagstaff. It was like 105* in the valley and I was about 24k lbs GCVW. I had Evans waterless coolant at the time and a hole in my radiator cap. Coolant temp would go past normal anytime EGT went over 1000* (i had ****ty toons back then...). I could hear fan engage, but it was LATE (already hot coolant) and weak. I was able to make it home by driving very conservatively on grades - that haul up to flagstaff is a bitch, nothing else like that on my way home.

 

Holding pressure should be an indication there are no leaks in the system. This should rule out cavitation, etc.

 

Ok, thanks. That's kind of what I was suspecting. Is there any kind of test? My dad said when he used to work on cars I'd you could spin the fan backwards it was bad. Riffraff is out of them so I guess rockauto. Was going to go motorcraft because the other ones seem like they'll be loud all the time. Any recommendations otherwise?

 

Should have more in this morning, just unloading pallets now.

 

ok, i'll check again later. I put in for the email notify. Thanks!

SSJ, sorry I should have said collapsed. The hoses were collapsed.

 

Besides sound, is there another way to test the fan clutch? My EOT hit in the 250's a couple times on some long grades on a recent camping trip, but dropped back down to "my" normal temps once done with the grades. Can't recall the fan noise, but I also wasn't listening for it specifically. My truck typically runs in the 210's to 220's when towing. Not sure what is supposed to be normal. I have a DS 203* thermostat. But I have Torquepro setting reading EOT. Not sure what setting reads actual engine coolant if there is one.

 

I don’t know how to test the fan clutch. Mine is the only one I’ve ever replaced and had I not put my truck in the conditions I did, I wonder how long it would have been before I knew it was ‘broken’??

These engines tend to run cool under most conditions. There was a period of time when the ‘fan delete mod’ was popular for increased MPG. But, folks quickly figured out that when the engine works hard - it NEEDS all of that fan. Same goes for ‘electric fans’ - they cannot move the volume of air needed.

 

The sound of the fan turning on/off is unmistakable. I literally sounds like a jet turbine engine spinning up under the hood. My fan ONLY comes on when I slow down to take a 90 degree slow speed turn with the 5th wheel in tow and hot ambient temperatures. It will stay on for 5-10 seconds and then shut off.

When I had the MST, the fan would come on a lot more often, but I was running the engine much harder then in order to accomplish the same amount of work.

 

I found this info in a DieselWorld magazine article. Even though it is for an 88 7.3 it does explain how the clutch works.
My limited understanding of how to test the fan clutch would be if you try to spin the fan by hand, if it spins but has resistance, meaning it won't freewheel it's still functioning properly. If the fan free wheels it is broken and needs to be replaced. If the fan does not spin at all or is very very difficult to turn it is also broken internally and must be replaced.
https://www.dieselworldmag.com/ford/tech-qa/
I suspect your original fan-clutch isn’t engaging when it should. A poorly performing fan-clutch will produce a chronic overheating condition. Depending on engine load, you may see above normal engine temperatures or you may see excessive temperatures while towing up grades that cause you to pull over. What follows is basic troubleshooting tech for discovering whether your fan-clutch is operating correctly.

The factory fan-clutch should engage when the air temperature between the rear surface of the radiator and the fan-clutch reaches its pre-set engage temperature of somewhere between 165-205° F, depending on application. Factory fan-clutch calibration can sometimes be a little loose, and having a fan-clutch with a calibration near the upper limit (or not working at all) can result in chronic overheating and poor air conditioning performance.

A bi-metallic coil on the face of the viscous clutch controls engagement. As the air temperature at the coil increases, the coil expands, which in turn rotates a shaft and plate, allowing the silicone fluid to pass into the working chamber of the fan-clutch. Opening this valve allows the silicone fluid to circulate between a close-fitting grooved rotor and stator, which increases fluid coupling. This causes the fan to turn at a speed approaching that of the fan pulley. Engagement never reaches a full 100 percent, but fan speed is typically in the range of 80-95 percent of pulley speed, depending on engine rpm and fan loads.

The silicone fluid is continuously cycling between the reservoir and the coupling plates while the valve is open. Once the temperature drops below the engagement point, the bi-metallic coil closes the valve, and most of the silicone fluid becomes trapped in the reservoir. This uncouples the rotor and stator, and the fan-clutch disengages.

You should hear more fan noise when the fan-clutch is engaged. Some people describe this as a “roar,” but there’s no mistaking the sound when the fan-clutch is fully engaged. You should hear the fan while pulling away from a stoplight on a hot day in city traffic or when the engine temperature reaches or exceeds 210 while towing up grades. A correctly operating fan-clutch is as important as any other single component in the cooling system.

Many people don’t realize that a viscous fan-clutch doesn’t last forever. Over time, heat slowly breaks down the silicone fluid or the fluid can sometimes slowly leak out of the clutch. Replace the fan-clutch whenever it doesn’t engage in situations like those described above. Good luck.

 

I replaced the clutch on mine with a genuine Motorcraft and for the life of me I still can't figure out if that thing works right or not. Seems like it is either engaged for partially engaged more than it should be and I can definitely tell the difference in noise and drag on the motor with it installed vs. removed from the engine. It has a fairly heavy viscous resistance when I try to move the blades by hand with the engine off either cold or warm. Two other 7.3's the viscous resistance felt about the same to me so IDK. Maybe I got a "tight" one because it seems like it works a little too well.

What do the fan blades feel like yours with the motor off? (OP). The other thing that I noticed was it sounded like you probably should have replaced the oil cooler when the old one started leaking. I've briefly seen EOT's in the low 230's when pulling a grade with a 13k 5th wheel in summer heat but it quickly settled back down to 215-220 once it flattened out. Far as I know the oil cooler is original but the rad is newer.

 

Usually the water is within 5-10* F of the oil, with the oil being the hotter of the two. The rad should be hottest at the top but will show cooler on the bottom as the water trickles through the passage ways and is air cooled. Try aiming your IR gun at the water neck or onto the pump itself and see how it compares.