I'm pretty sure that's what it is. Seems gearing is everything in this situation. I can WOT pull a hill with the 5th wheel in tow at 65 for miles, but cannot even go straight and level empty at 75.

 

kwik is your fan metal or plastic

 

Plastic and I think it's the same size as any other powerstroke.
I should go measure it and post back, but that will have to wait until tonight.
I sure would like to get to the bottom of this.
My two previous F-250 460 gassers would do the same thing, but without the annoying speed limitation. I could work them as hard as I could and no overheat or belt slipping. But the fans on them would not lock up as hard at high rpm as the PSD does. I could be pulling a hill with the AC on, no problem at 3000 rpm. As soon as I crested the hill and could upshift the fan would lock up harder and get louder until the engine cooled off again. The fan clutch would slip a little at high rpm to allow the engine to spin up, but not drag the belt like it does on my PSD.
The PSD fan simply refuses to allow any of that high rpm slip and the weakest link (the belt) slips instead.
Maybe I have a bad fan clutch. Really at a loss for an answer on this one because it SEEMS to be functioning properly and this is the first Ford diesel I have ever driven, owned, you-name-it. So the learning curve is steep.

 

might be completely unrelated but had a similar experience with my last L-9000 someone recomended a Flex-A-Lite fan and it worked
was also at least half the weight

 

Dan, I wold look real hard at the belt/tensioner/fan clutch assm. My 550 cooling fan cycles on and off without slipping the belt. Towing or not it seems to cycle about the same and as often. OH AND BY THE WAY, THE US GEAR 2SPEED IS INSTALLED!!!!!!. Finally, its in and the tests are under way. Initial response is ITS AWWWSSOMME.

 

I was hoping you would chime in here because you have a 550 as well.
Thanks for the tip.

And now I have OD envy.

 

Well since I'm retired, I make it a point not to drive in stop and go traffic, I'm usually enjoying a cold one about that time. The few times I've gotten slowed by road construction while towing, I've always turned the A/C off anyway and opened the windows to help keep everything in the engine compartment as cool as possible until I can get underway again.

I think with the A/C mod which eliminates the need for the A/C to cool the residual supply of hot coolant, the A/C will work fine with the Genedad 2 mod as long as you have some steady forward speed. But like you said, if caught in a complete grid lock you might have to turn it off and roll down the windows.

If you've ever towed and listened to the incessant roar of the cooling fan in full lock, and then compare the much reduced operation of the fan which is also much quieter with my mod, rolling down the windows once in awhile won't seem like a bad tradeoff at all!

 

I was in a hurry, and didn't duct tape my remote read out thermometer to the under the hood fuse box which is how I make my on the road measurements. However, I'll make some of those measurements as I continue my travels and report them. I did a couple of spot measurements of the turbo inlet boot at rest stops with my IR thermometer, and it was about 10* cooler than previous measurements.

The viscous fan clutch doesn't go into full lock until about 205*, and that temp gauge definitely showed a big improvement because the fan hardly came on at all, and the few times it did were near the tops of long grades, and the roar of the fan was much reduced compared to before, and wasn't at all bothersome, just a nice whine and the sound of rushing air through the engine compartment.

As you can see from pic #2, there's now a lot of the IC exposed directly to the incoming ambient air flow, so that's got to reduce EGT some. I think EGT's were a little lower, but I was trying to watch my CFM gauge which is on the floor, and my BP to get that data while I was pulling grades. I really need to get a video camera so my wife can tape all my gauges when I pull long mountain grades.

 

Well maybe my use of cavitation wasn't the best choice of words. Letting the fan pull some air directly over the top of the A/C condenser and through the far less restrictive IC and radiator definitely reduced the roaring noise that the fan previously made. The new noise isn't that objectionable at all. You can pull that top mat off in 5 minutes, and mine came off with all the plastic stick pins in tact, so it would only take 5 min to put it back. I think you'll find that letting the cooler RAM air flow over the top of the A/C condenser keeps the clutch from locking up as often, and the fan noise is much reduced as well. Since the fan is now pulling the more free flowing air and doesn't have to work as hard , it should take some of the load off the fan belt so that it might stop slipping as much or not at all.

 

Watch for my new post giving my analysis of high altitude effects including boiling point depression, HP loss for various boost pressures vs altitude, etc... I started thinking about the boil over analysis as I watched Old Faithful erupt, and saw all those pools of boiling water everywhere!

 

Interesting place to be. I love it there. Did you make it up to Mammoth? It's a sad developement up there, some seismic activity cut off most of the water supply there and now it's just a collection of grey hills where there used to be those beautiful white cascades.

On the subject of boilover and altitude: I know if you stick a cup of water in a vacuum chamber and evacuate the air it will boil at room temperature. Ok, now let's go the other way for the sake of curiousity: How hot does the water have to get deep underground before it starts to flash to steam?
Just for the sake of numbers let's assume the column is 1000 feet deep and the water is filling it up to 950. And the heat source is at the bottom of the column.
How hot does the water have to get at the bottom of the column before it starts to build steam pressure and cause Old Faithful to erupt?

But now after typing this all out, I realize that this question would be better asked in that thread, so I'll look for it there.

 

Why does altitude have an affect on our SEALED cooling systems? I thought that's why they were sealed in the first place (to raise the boiling point a bit).

Joe

 

A lot of this discussion is about the flow of air getting through the condensor, IC and radiator. As you might imagine, once the air is in the engine compartment, it must flow out, or no more air will get in! The engine and firewall effectively are air "dams".

Gene, is this why the fan cavitates - because it can't pull any more air into the engine compartment because of the "packed" air that is already in there?

Some earlier Super Duties, such as IDIs I believe, and my 2001 Excursion have a black plastic strip that goes across the front of the truck, underneath the bumper. I'm not sure which, if any, later Super Duty trucks have this strip. The purpose of this strip is to create a negative pressure area under the engine compartment while the truck is traveling down the highway. This negative pressure "sucks" the air from the engine compartment and allows more air to enter through the condensor, IC and radiator.
The idea of this strip is brilliant and CHEAP! The early IDI engines had overheating problems if this strip was missing.

Will this information spark some curiosity and maybe some more experimentation?

 

I'll definitely look into the strip idea, and I can even make some differential pressure measurements between the engine compartment and various locations under the truck using my special two port gauge. I've decided that a hood vent to let hot air out of the engine compartment that way is probably not the best approach, because that will encourage the hot air from the exhaust manifolds to flow up and past the air intake system heating it, and that would be counter productive by reducing the air density into the engine. It's much better to create a negative pressure underneath the engine compartment and get rid of the hot air that way.

Check my new post on the cooling system, I've given more details there of my analysis leading to the Genedad 2 mod, along with estimates of cooling system capacity due to RAM air flow. I can tell from how often the fan comes on, and from the new sounds with the fan locked up that the Genedad 2 mod allows a higher CFM flow through the radiator core. The problem was the restrictive A/C condenser, and letting the fan freely pull air over the top of that restriction and then through the far less restrictive IC and radiator has greatly improved the cooling of both of those, and supplied more CFM of cooler air to the engine compartment as well. It will be interesting to see how many inches H20 difference I get between inside the engine compartment and under the truck.

 

I've got a question, if the goal is air flow why does your truck have front license plate sticking straight up into the lower grill opening? If it is a legality issue the plastic rivets that hold it on can be drilled or broken out and the plate mounting braket can be rotated down using the top holes of the bracket in the lower holes of the valance with 1/4" bolts. The plate is still readable, which make it legal (in Ca) and it opens a large hole for more air. Just my .02.