I have a F250 7.3L powerstroke that I think is great. The problem I have is the sound of something changing RPMs while pulling heavy loads during the summer. When pulling up hills with the engine RPMs at 2600 and greater, it sounds like the fan clutch is engaging and disengaging at about a 15 second intrerval. The tach shows no RPM change and it runs smooth and pulls fine just the sound of something changing RPMS. Below 2500 RPMs I never hear this sound. I can't seem to reproduce this noise unloaded at the same RPMs. The local dealer says it's the fan clutch and its normal. Is he pulling my leg or do I have a problem??

 

Sounds right to me, when the fan clutch kicks in for more air flow, you will hear the roar. You should also hear the roar on hot days above 90 degrees with air running. You'll hear it when you come to a stop and then start moving again, it will roar until you get going in high gear and faster. You've got a pretty good load to be running 2600 rpm but I guess going up hill, which there aren't many in Texas where I travel, you would be in 3rd rather then overdrive. Your engine is producing a lot more heat when towing because of the extra fuel being used and therefore more heat to dissipate from the cooling system. Next time you get a chance, turn off the air conditioner for a little while and go uphill towing, you might not hear the roar because of no heat from the a/c condensor. You have to have the a/c off for a little while and allow everything to cool down some when you try this. Don' expect to kill the ac while climbing a hill and instantly get the fan to kick out of high speed, run a little while with no a/c.

 

I might have had a similar problem. My fan worked like it should when pulling my horse trailer at 75 with a\c on. But my fan sounded like the fan was changing pitch or clutch was slipping then going back to normal. I had my mechanic replace fan clutch and it worked for a while but came back after 15 - 20k miles. Never did figure out what it was from. Fan worked as is should and engine never over heated. The truck in question was a second gen 99, auto and 3.73 rear end. In my opnion, I don't think the a\c was the cause of the problem. I have always towed with the A\C on and none of my other trucks did anything similar.

 

I hear a noise like that too whenever im towing around 70 mph with the overdrive off, pulling around 2600 rpm, its a kind of quiet, but distinvtive squeeking noise, like a slipping belt or somthing and the fan stops spinning, than it kicks on again and stops. It always worries me so i kick it into overdrive and it never makes that noise again. But i have heard that towing in overdrive is a major no no, but i cant help it, I just dont like that squeeking noise! If anyone knows what it is please help before i go nuts!

 

Try a Hayden fan clutch and see if the problem goes away.

 

Thanks for the input. Still not sure how the clutch could cycle every 15 seconds or so. I can understand how it could cycle over a few minutes as the temp increases. Another thing, I didn't know you shouldn't tow in overdrive. Nothing in the owners manual about that. Never seemed to cause any problems, is this a no-no???

 

When I had a 2001 F350, I would hear a noise at high speeds. I made the dealer replace the plastic blade and fan clutch. The noise went away.

 

Found this in my saved notes folder:

2002 F-Series and Excursion Belt Squeal; 99-01 with Replaced Belts:

"Some 7.3 engines may exhibit a loud squeal noise from the engine area when the engine is under load and the fan clutch is locked up, typically in hot and dusty conditions. Another complaint may be the fan clutch oscillating or not locking up. This may be due to dust accumulating on the back side of the belt and causing it to slip on the water pump pulley. This usually affects only 2002 model/year vehicles, but may occur in trucks built from 99-01 if the belt was replaced after July 01. A service kit is scheduled for release in 2003, but in the meantime, replace the serpentine belt with P/N 1C2Z-8620-NA on single-alternator engines, and 1C2Z-8620-PA on dual-alternators. Broadcast Message 3848.
On trucks with dual rear wheels(?) use 2C3Z-8620-AA for single alternator and 2C3Z-8620-BA for dual alternators. Broadcast Message 0290."

The "kit" they refer to includes a new belt, heavier sprung tensioner, and water pump pulley. Saw this posted elsewhere and kept it for future reference. Just might be the answer.......

As far as not towing in OD, that's pretty much from the "old school" towing bible. Rule of thumb: As long as the trans is not constantly "searching" and shifting (which would cause excessive tranny temps and ultimate demise of same) towing in OD is pretty much the norm.

Hope this helped ya......

 

Well I was told by the mechanic at the Ford dealership not to tow in overdrive, he said that these motors were built to operate in the 2700-3000 rpm range. I dont know if that is true, but a mechanic would NEVER lie! haha, anyways i still only tow with overdrive off in the hill's or in traffic, but on straight highway i kick it into overdrive and let it roll

 

I tow a 13,000 lb. 5th wheel rv all over and seldom have to drop out of overdrive. If the trans. is not hunting, things should be OK. I haven't realized abnormal temps or fade, shift malfunctions or noises from trans. I would hate to think of running my '01 PSD at 2500-3000 rpms all the time I'm towing, since the "redline" is approx. 3100 rpm. I would think that would help to shorten the life expectancy of the engine.

Bill in KY
LUV my PSD

 

Update....It seems that ambient temp above 85 deg F is where the cycling occurs most. I live in Az and most of the summer the ambient temp is 90 or above. The fan must be engaging looking for cool air and isn't finding it. I think I'll try the new belt kit and then maybe a new fan clutch..............Thanks for the input

 

I have an E-350 van and have had the same problem., Does your unit loose power when the fan is Cycling?

I recentlly towed my 6k camper on the trip out ambient temp 85 no problem, on the return trip 92F fan cycled several times robbing power.