Running with no engine fan?

[Loren]

The only time the factory fan clutch on my Cummins has engaged is while pulling a trailer in the mountains in the summer. The engine barely stays warm in the winter. Will it hurt anything if I remove the fan during the cold months?



Is this a feasible way to cut down on some horsepower losses? It seems like it would be a lot cheaper than a Horton fan clutch, and do the job just about as well.



If this is an acceptable procedure, how do I remove the fan? It looks like removing the bolts through the fan will just loosen the fan clutch, not the fan. If this job is too difficult, it may not be worth it, just to get an extra 0. 1 mpg.



My goals are to get a slight power increase, a slight increase in fuel mileage, and a noticeable reduction in noise.



Any thoughts on this subject?



Loren

 

[Don M]

A bunch of us do it. I do. Less noise and it never gets hot.



Don~



there are several threads going on right now about this.

Some say as much as 25 HP. Dee Rawson got a dyno reading of 19 HP saved at 190 degrees.

 

[icarus33]

Loren,



You want to loosen the large hex nut, about a 1 7/16 wrench needed, and is reverse thread. This removes the fan and the clutch. Use another bar or screwdriver between the frame and one of the smaller fan bolts to hold it so it does not slip when turning. You'll likely need a cheater bar the first time since it will be very tight.

On my '98, I don't take the fan shroud or top radiator hose off. I just turn the fan and wiggle it out. It's about a 10 minute job once you have the tools.

The one warning I would have is that if you have an automatic, keep in mind that you have now stopped all air flow through the fluid cooler when the truck is not moving. With my transmission gauge in the hot line from the torque converter, the highest I have seen is 210F, with outside temps in the low 50's, still not bad. Driving with O/D off so lockup occurs at lower speeds helps considerably too.

 

[JJW_ND]

Watch how you use AC, Defrost....

I have ran fanless for two winters now. Only put it back in for the three months of summer. On 97 and older trucks it was pretty easy to disable the AC compressor from coming on in Defrost. You want to watch that as when not moving and defrost on you will over pressure the AC system. It is easy to forget.



So remove the relay/ fuse to keep the AC compressor from running when fanless.



I have pulled a 20' stock trailer through the blackhills of SD with temps in the low 80s running fanless. No engine heat problems.



jjw

ND

 

[Loren]

JJW,



I don't understand why removing the fan should affect the air conditioning. I know that the air will not flow across the condenser as well, but how could that cause the system to over pressure?



Glad to hear your report about the trailer in 80 degrees. The only time my fan clutch has engaged is pulling a trailer over the Appalachians in June.



I intend to unscrew the fan this evening and check the difference tomorrow morning. Thanks for the reports.



Loren

 

[Texas Diesel]

The A/C compressor runs in the windshield defroster is on.

 

[WestTN]

no fan

Well, when the fan hub is in idle mode there is vey little power being used. You will not find large fuel mileage gains. I tried electric fans on my old truck and never saw any significant fuel savings. The fan only uses a lot of power when engine cooling requires it. My old truck is back to fan and shroud operation. The AC works good again.



All of my fuel usage is recorded. I've got 224,000 miles of history on the old truck and 10,900 on the new one and will NEVER run an electric fan again. The stock one can't be beat and the price is right. Just leave it there.



MHO. Your mileage may vary!

 

[Loren]

I still don't understand why removing the fan should affect the air conditioning. I know the air conditioning compressor runs when defrost is selected. On my 2000 model year truck, it runs occasionally in all heating/air conditioning selections except for floor only.



How does having the compressor running without much air flow over the condenser cause problems?



I took the fan off last night. It was really easy, about a 20 minute job, and I have never done it before and was being really careful. Today I ran all over town and put about 125 miles on the truck. I couldn't tell any difference most of the time, but at 65 mph or so, it was quieter. Not a lot quieter, but I could tell a difference. It seemed like it had a bit more power, but that may have been psychological.



I intend to fill the fuel tank tomorrow, and then I'll be able to check for any mileage improvement. I also keep meticulous records, so if there is a significant change, I'll find it. The reports for the Horton fan clutch usually include a mention of a mileage improvement of 1-2 mpg. This should be an equivalent situation. Time will tell.



Loren

 

[WestTN]

Loren, The AC needs a good amount of air flow across the condenser. That is the thin unit on the outside of your radiator. It removes the heat from the refrigerant. This is a vital part of the process we call air conditioning. If you interfere with the cooling of the condenser, you can damage the AC system. Inadequate air flow causes high head pressure in the compressor.

 

[JJW_ND]

MPG is if no interest at -30!

Some of us running fanless have nothing to do with getting better mile per gallon. Just trying to keep a little heat in the truck. The thermostat never opens in temps that cold. No need for a fan. Even with everything buttoned up (winter front) you still have to work the engine to get any heat into it. Once warmed up, seems like a waste to have the fan remove what little heat you were about to create. Pulling off the freeway and idling for less then 5 minutes drops the coolant below 150.



With a winter front on, and driving over 70 for more then 100 miles in temps below -20, engine oil temps are not even 175. Manual transmission oil temps are less the 70. Coolant about 170. Truck runs fine, sounds loud and blows plent of heat.



BTW, when running in sub zero temps, the clutch fan sounds like it is full looked. Lots of drag!



jjw

ND

 

[WestTN]

The fan clutch will always be activated when shut down. The coupling fluid leaks back into the main chamber. It does release within a minute or so after startup. Meanwhile, that extra drag places a little load on the engine to speed warmup. With a winter front on the grille there is nowhere for the fan to get cooling air to cool the engine.

 

[Loren]

I have had the fan off the truck for several tanks of fuel now and thought that I would be able to post some information about fuel mileage comparisons. I can't though, because I'm trying to compare apples to oranges.



I do keep meticulous records, but I also pull a trailer occasionally. It's not even always the same trailer. I found when I looked through my truck's logbook that I often didn't fill the truck with fuel when I hooked up to the trailer. That means that I have several tankfuls with some empty miles and some pulling miles and I can't compare those mileages with others, because it's not consistent.



The best I can come up with is one tankful recently that was empty for the entire tank. That mileage was 17. 8 mpg. The last non-trailer tankful I ran through the truck before I removed the fan was back in September, and that mileage was also 17. 8 mpg.



I don't like using just two tankfuls as a comparison because so many things can vary between tanks: highway vs. city driving, lead foot vs. easy acceleration, hilly terrain vs. flat, etc. Even so, it's interesting to note that on those two tanks, I got exactly the same mileage. Removing the fan didn't improve fuel mileage at all.



Have any other members kept good records? Have you seen mileage improvements after removing the fan? So far I'm skeptical of the claims.



Loren