My Fixed Flex Fan mod

turbobill · **Posted:** Tue May 22, 2012 6:49 pm

No new news in this post except my experiences and thoughts about the FFF mod. I had planned on doing the FFF mod this spring in anticipation of another long hot summer in Texas. I pull a bass boat, often up some pretty steep grades and had noticed my CRD warming up last year. My viscus fan was operating by only when cooling temps approached 240 dgF, a little too warm for my taste. I chose the FFF mod o9ver the Hayden viscus replacement because I felt that it would also help with A/C efficiency and Help keep my transmission cool during city driving.

I lost my electric fan sometime in late winter, early spring. I noticed that it was not working when my A/C was not working at idle and the compressor was cycling about every 1 to 2 seconds. The fan was full of black soot so it had burned at some time.

As soon as I installed the fixed fan my A/C worked at idle again, in fact better than ever, so I believe my supposition that I would have better A/C efficiency during city driving was born out. I have had opportunity to pull my bass boat up my long hill in 90+ temps in the past two weeks and there is not even a hint of warming up. My temp guage is one of the 2005's that left the factory programed for a Gasser instead of the diesel so I can see fairly small temp increases in the cooling system. The CRD is a little more slow to heat up, maybe takes 4 or 5 miles instead of the one mile it took with no fan.

I have cut off the bottom of my fan shroud so that I can remove the shroud without removing my fan, thus making a fan pull MUCH easier. I intend to pull the fan when daytime temps return to low 80's in the fall.

I did not use the fan suggested by kapalczynski in his original post and my fan was fairly aggressive, about 21/4 inch pitch. This made the fan pretty noisy so I pulled the fan and flattened the SS sheeting to remove the aggressive edge of the flex fan. The pitch is now about 13/4 and is barely noticeable, but still does a great job cooling. This fall I am considering removing the back 1/2 to 1 inch of the fan blades, it looks to be doable. For those that would consider the FFF mod I would suggest that you search out the least aggressive fan you can find. Papaindigo used the fan that kapalczynski recommended and I believe he said it had about 11/2 inch pitch. kapalczynski also used a 19 inch fan, as did I, but I would drop down to an 18 inch fan. A low pitch, 18 inch fan should provide very little,, if any, increase in operating noise, although I haven't personally tested it. I used a 1 inch adapter to position the fan blades away from the engine block, but I think another 1 inch spacer would place the fan in the shroud sweet spot and help with some noise as well. The next time I remove and reinstall my fan I will add another 1 inch spacer. Total cost of my FFF mod was a little over $100, including delivery costs.

For me and my use of the CRD in my climate, central Texas, a fixed fan is much better than the viscus fan solution. I get improved A/C efficiency and better cooling for my transmission fluid for city driving and do not rely on my electric fan operation for good cooling with the same driving conditions. Also I get the improved cooling I need for towing my boat in our super hot summers.

I did replace my electric fan. I used an aftermarket fan from Hayden and modified it so it fit in the existing fan shroud. (see separate post). So far, with my FFF mod, my electric fan has not turned on. I did fully test the fan by jumping my high and low speed relays to ensure the fan worked as advertised. I think the fixed fan keeps everything cool enough the fan sensors are not actuated.

The FFF is a great mod, I recommend it for anyone living south of the Mason Dixon line and is a no brainer if your viscus fan is not working. Consider it.

TJ2 · **Posted:** Tue May 22, 2012 7:46 pm

I did the FFF mod and was pleased with the results. I put a Hayden 2905 clutch back on for winter driving.

I drive a nearby mountain pass that will heat an engine up and cool one down quickly. . . depending on the time of year. Last winter I lowered myself down in 2nd gear to keep engine warm. Will remove fan altogether next winter.

Now that I have a fan removal tool, I might put the FFF on when out grinding around in 4-low.

racertracer · **Posted:** Tue May 22, 2012 8:04 pm

TurboBill,

Glad you have the fan working the way you want.

Can you post part numbers and sources?

Racer

papaindigo · **Posted:** Wed May 23, 2012 9:03 am

Kap's original parts list is at viewtopic.php?f=5&t=51618&hilit=fixed . I was curious why 2 washers until I got looking around and 2 are needed to clear the AC compressor "nose". For what it's worth Kap's thought on noise was that going deeper into the shroud would increase the noise. Of course how that would play out for a shroud without the bottom 1/2 is anyone's guess.

FYI the fan in Kap's specs is a 2.125 in pitch. I notice fan noise a bit around town between 1500 and 2000 rpm but on the hwy there is essentially no extra noise.

racertracer · **Posted:** Thu May 24, 2012 4:42 am

Thanks Papa.

turbobill · **Posted:** Thu May 24, 2012 3:54 pm

My part list:
Adapter - Flex-a-lite part number 851 - 30 mm x 1.5 pitch flex fan adapter
Derale 17619 Heavy Duty Fan Blade Series 1000 19" Stainless Steel Flex Fan Reverse Rotation
Mr. Gasket 2392 Aluminum Fan Spacer Kit

The adapter is the same on used in the original FFF mod. The fan is different and I used the 1 inch spacer. All of my parts were ordered from Amazon.com.

When I install my second 1 inch spacer to move my fan forward in my shroud, I'll post noise impact. My concern on noise is the buffeting against the front or the engine, with the original install there is very little room at the back of the fan for the air to move out. I have done a lot of work with laminar flow of water in my past life so I know this can be a problem. Whether there is a noticeable is the question. Frankly, I am happy with the noise lever of my setup right now. Very little "extra" noise, maybe drowning out the diesel clatter a bit.

As secondary effect I also noticed is that since I have ORM and EHM mods my engine would stop abruptly when the ignition is turned off. The fixed fan seems to have enough momentum that the engine shut down is MUCH smoother now.

As I said in my post I would not use the fan I used but would look for a much lower pitch fan with 18 inch diameter rather than 19. My guesstimate measurement of the OEM fan is that it is 18 1/2 inches. Hard to be accurate with a five bladed fan and a tape measure. If it is reducing the diameter to 18 inches is only a reduction of 1/4 inch in the radius. Probably no impact on cooling but a lot of noise comes off the ends of the fan blades where there is the highest rotational speed.

My thoughts.

turbobill · **Posted:** Fri Jul 13, 2012 10:24 pm

It has been 7 weeks since I installed the fixed flex fan. We have seen plenty of super warm days in Austin so far with temps at or above 100 and my CRD continues to run cool as a cucumber when towing my bass boat. Under worst conditions, high temps and slow, uphill driving, the engine will warm to about 19o but most of the itme it sticks with the thermostat controlled 176. I am very pleased with the mod and would recommend it to anyone towing south of the Mason Dixon line.

papaindigo · **Posted:** Sat Jul 14, 2012 7:13 am

I've got a spare fixed fan hub and washers in need of a good home. If interested PM or email

No longer available as a home has been found.

My Fixed Flex Fan mod

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