Background: 2012 F350 DRW PS used almost exclusively for towing our 15K lbs. home on wheels. The truck currently has about 60K miles on it (yes - six zero thousand).

We left Aberdeen Proving Ground, MD, this morning about 9:45 this morning heading west. The temperature at that time was 86 and the relative humidity was 67% (can you say, "Muggy!"). Within an hour and a half, I saw 92 on the truck thermometer, but it dropped into the upper 80s again due to some clouds and a couple of light showers by the time we started hitting the 6% grades east of Cumberland, MD. Climbing, I keep the turbo below 20 and this usually means 5th gear at about 2K RPM in the truck lane. The engine temp climbed a little, but never more than a couple of needle-widths above center; the tranny temp never waivered. Going down the other side of the grades - also around 6% - I use the manual transmission mode in 4th and 5th tapping the brakes occasionally to keep the RPMs below 2,500. I don't know how the fan(s) is/are driven, but after about a minute on each down-grade, the fans would start howling like banshees - like the fan clutches fully engaged... you know, like an old ****** Jeep (don't know if this truck has fan clutches or not). Nothing wavered - turbo, RPMs, or transmission temp. The engine temp, of course, would head back to left of center as I would expect, but the fans continued to howl while using the engine brake. Once leveling off and applying power again, the fans would quiet down and everything would sound normal again.

I've driven this rig out west where grades and temperatures can be more severe and never experienced this before. Is this something I should be concerned about? Would the high relative humidity have anything to do with it (cooling efficiency - high RH affects the way aircraft perform)?

Can anyone enlighten me on this?

Thanks,

Rob

 

Think you are worrying too much. Just drive it and let the PCM/ECM do the thinking for you on fans and all. Not sure why you lock out 6th gear. Never had any problems in the mtn's out west during the hot summers.

and the sound of the fan's bother you, ,turn the radio a little louder....

 

Thanks. I tend to (worry, that is). As for "locking out 6th gear," I don't. I just use the manual mode going downhill to keep the ECM from shifting down and raising the RPMs every time I touch the brakes. I put it back in regular tow/haul mode as soon as I reach the bottom (climbing is always regular tow/haul mode).

Thanks again for the input.

Rob

 

Ford copied Caterpillar on this; when enough engine brake is needed, the PCM will engage the fan clutch for added braking horsepower.
Both my ‘15 and my ‘16 would do this under the right conditions. The last trucks with Cat engines I drove did the same thing.

 

Thanks, Don - makes sense.

We're headed your way... we'll winter in Las Cruces, NM, this year (my home town).

Rob

 

I get engine fan action when the A/C is on. I'll have to keep an eye out for the situation that Desert Don posted. I don't think I've observed that, but when going downhill, I'm a little busy. I worry more about going downhill than uphill.

 

I run it 70 mph up I 68 with cruise on and let it do its thing.

Running down the other side I abide by the truck speed limits for the down grades.

Clutch fan will come on high and just let it run. It does fine.

 

A bit late on the follow-up, but here's what I found out... I'm paranoid enough that I couldn't continue another 1,500+ miles without knowing for sure that the truck was OK. I made an appointment with a Ford dealership in the Cincinnati area and they ran it through a complete diagnostic panel paying special attention to the fan clutch, temps, etc. The truck passed with flying colors. In retrospect, here's what I think happened. This was the first long-haul towing we had done with our new Solitude. It is heavier and presents a larger frontal area than our previous Reflection fifth wheel. Temperatures were also significantly above average during September and October in the areas where we were traveling. As a result, the engine and transmission temps, although still normal, were warmer than we had previously experienced. As soon as the weather cooled down - even when we got out west with a lot of elevation changes - the fan noises quit. Thanks to everyone for their input.

Rob