Good afternoon folks, has anybody decided to go the electric fan route with these bullnose trucks? What do you recommend? Is there anything out there I should avoid? I am still concerned about my cooling problems and trying to decide what's best in the long runs. Heat is a constant enemy here near Houston, Texas. & and this bullnose is being built for long (50+m each way) highway drives in hot slow traffic. What do you think will fit? What would you run? it is a carborated 4.9l, with the heart shaped head and HEI ignition. MIA on the EGR. Stock 84 v belt systems. Thanks for any advice you can give me.

 

Some questions:

Are you presently experiencing cooling problems? Your post isn't quite clear about that. If so, under what conditions, such as stop/go or freeway driving? Does your truck have factory AC and the temperature gauge rises when the AC is on?

How strongly do you have your heart set on an electric fan conversion? Is it something you just gotta have and trying to talk you out of it will tick you off? Or do you just the cooling system to work properly and don't care how you get there?

As you may have guessed by now, I'm no fan of electric fan conversions. My car came from the factory with an electric fan and the whole thing works great. But that's also a factory designed system, with a proper shroud, integrated computer control, a mega alternator, and beefy wiring. Most home conversions I've seen are just the opposite and do not perform well.

The factory cooling system (with belt-driven fan) works very well, in my over-inflated opinion. Given the chance to spend your time and money, I'd much rather make sure that system is in top shape instead of gambling on an electric conversion.

If you absolutely have to go electric, one important consideration: Install the fan in a puller configuration, on the aft side of the radiator, if at all possible. Any fan loses about 30% of its airflow centrifugally. A pusher fan loses that airflow before even passing through the radiator core. With a puller configuration, at least the air passes through the core first. This is why nearly all factory installations are pullers, for maximum efficiency.

 

I am having cooling problems. I do have ac but my cooling problems present even before ac is engaged. In fact i am currently in a break in phase on the engine and struggling to run it for more than about ten minutes before its too hot. (I have multiple issues im working thru)I have pushed the timing up to about 12’ adv and that seems to be helping. I have new hoses and radiator. The pump appeared fine when installed and both upper and lower hoses are hot so water is moving.
I traded out the stock clutch fan for a derale flexlite fan and i suspect that was a mistake. While it rotates at 1 to1 at all times, the blades themselves are shorter and shallower. So i suspect it’s not really pulling the air the way it should be (and may not be deep enough in the fan shroud) . I am not committed to any coarse of action just yet, but im leaning towards first replacing the clutch and reinstalling the original clutch fan. If my problem persists beyond that i know its probably timing or head gasket related.
Then i was also considering a couple of 10” pusher fans as a back up or assistant to the stock set up. Im not a real fan of relying on electric cooling. I was considering he 97-98 Lincoln mark VIII as its a known performer. But its 100’ outside i dont feel like spending a weekend looking for the radiator fan assembly in the salvage yards.

 

This plan seems reasonable and prudent. I'm no fan of those flex fans. I'm much more partial to the stock rigid fan and a clutch drive. I know many people insist a direct drive must be better, but I disagree. Slippage, that must be bad, right? Not if intentional and part of the design. In my over-inflated opinion, a flex fan with direct drive is probably the worst combination.

How can that be bad, with the fan running at full RPM? One problem with a direct drive is the fan will now spin too fast at higher engine RPM. Faster means more cooling airflow, or so it would seem. How can that be bad? The curvature and angle of the fan blades is designed to be most efficient moving air at a certain RPM. Exceed that by too much, and the airflow is no longer smooth. It becomes rough and choppy. The ideal is a smooth flow of cooling air through the radiator core, where it really matters. Instead, you end up with this swirling angry mass of turbulent air behind the radiator, which unfortunately limits the desired cooling action.

A radiator fan clutch is a key part of a carefully designed system that works very effectively. I would not recommend trying to change that equation. It sounds like the new flex fan doesn't fit the existing shroud very well, either. Just that issue alone is going to limit cooling airflow through the radiator.

 

I am with Karl on this as I also am not a fan of the converted electric fan club most do not cool and they are posting "it now over heats!"
There is nothing wrong with the factory setup as it work when it left the factory did it not?

First I will tell you what I have and how it works in the 95*+ summer heat with AC on and slow traffic.
81 F100 300 six, factory AC, Alum & plastic radiator, fan shroud, and 4 blade fan bolted to the water pump.
AC trucks used a clutch fan but I did not get one with the truck and this works for the most part.

Now on yours I see the fan to radiator shroud, you have a shroud right? may be a problem.
Fan blades need to be half way in the shroud opening. So if the fan blade is 4" then 2" has to be in the shroud and 2" out.
If too far in the fan pushes air into the back side of the shroud and not out. If it is too far out it will not pull air thru the shroud but from outside of the shroud.
Also the blades should be as close to the shroud with out hitting but the rule is about 1" so the motor can move with out the fan hitting the shroud.

You did say the upper and lower hoses are hot but do you have a spring in the lower hose?
New hoses DO NOT come with this spring, you have to reuse the out one.
No sping in the lower hose can cause the motor to overheat because of no flow. The lower hose is on the suction side of the pump and when the motor RPM goes up so does the suction and the hose closes stopping coolant flow. So lower hose needs a spring.

The only time I have had the temp go up was sitting with AC on for 20 minutes waiting for someone and it was 95*+ out.
As soon as I started moving / driving the temp came right back to normal. I am sure if I had the right fan blade or more blades it would stay at normal temp when waiting.
BTW my 02 Durango has a motor driven fan and electric pusher from the factory and only run when the AC is on.
Besides more blades it looks like it could be a little larger but it been working 6 years now even when pulling a 20' enclosed trailer.


What is the "too hot temp" do you have a number or where is it on the factory gauge?
Get the fan fitting right in the shroud and you should be good.
Dave -----

 

I have ordered a new clutch for the original fan. Im leaning towards condemning this set up . It clearly is not working. As for the how high is to high question the first time I noticed it around 250’ after that i shut it down and kept my test runs short and monitored, shutting down around 220. I pushed the timing up to around 12’ btdc, filled with cap open, overflowing a time or two. The radiator itself is new now. And i have a fan staged in front of the truck to help keep it cool while testing until the clutch arrives. I am not defeated, i have just learned 1 more thing that does not work!

 

Can someone with a 6 cylinder show you, their fan and shroud ?
Mine's a 302, so the pictures may not help.
FWIW, notice how big my blades are.

 

Okay, gotta ask. What's with the 3 hose clamps? Was that just a convenient spot to keep 2 spares?

The fit between the fan and shroud doesn't look too bad at all. I wonder if the flex blades are flattening out and reducing the amount of airflow.

Do you have an infrared temperature gun? If not, we'll wait while you zip out to get one.
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Back so soon? Great. With the engine warm, measure the temperature at the radiator inlet and outlet. In good working order, the outlet should be at least 30F cooler. This tells us the radiator is doing its job and transferring heat to the passing airflow. If less than thst, there are several possibilities. The most likely is inadequate airflow. Another possibility is scale buildup inside the radiator, but that's not going to be an issue if new. Yet another possibility is loose crud restricting the coolant flow at the inlet tank. Once again not likely with a new radiator, unless some crud in the heater broke loose.

To test the airflow, hold a rag or sheet of paper in front of the grill. With the engine at idle, the rag or paper should be held tightly.

 

i had several methods to check the temp. The delta was closer to 15 last time i checked. The radiator is new and the block is a fresh rebuild. The paper test would stay but loosly not tight at all.
the 3 hose clamps were a quick fix for a slow leak that still needs a proper fix. While trying to break in the cam.

 

I would put the stock fan back in place, as said, Ford designed the system. You're the only one having issues... I'm sure others have driven these trucks for decades without issues.

Sorry, but why after a cam replacement there is a leaking hose that needs three clamps... shouldn't all the parts needed have been replaced. The hose is cheap money, compared to all the work done...

 

1. What are your methods of checking the temp?

2. Good thing you are getting rid of that fan you bought. I personally had one of those flex aluminum fans fly apart and a person I know had theirs fly apart also.

3. After the initial fill it will overheat. There is air trapped in the top of the engine, it will overheat till the thermostat finally decides to open. Then you have to quickly put more coolant in. It may do it one more time before it finally settles down.

 

Truck purchased ($1500) with a blown motor.Replaced motor, rebuilt transmission, many other new parts but you have to draw the line somewhere. Plan was to cycle in all new support systems progressively with annual maintenance cycle.

 

Yes sir, i expected as much, this is my first 300 rebuild, but not my first rebuild. Im thinking i got it all burped out at this time and temps are controlling better but my run times have been short as i have other issues to address right now as well. When it comes this far apart little things happen. And its kinda frankensteined together with some of my part selections.

 

Ooh, this is getting exciting! That temperature drop looks to be insufficient. And the result of the paper test doesn’t sound right, either. If indeed you’ve got low airflow through the radiator core, that would ‘splain a lot.

Keep us posted what you find after swapping back to the original fan setup. I would suggest resisting the temptation to make a whole bunch of changes all at once. For example, say you also rework the shroud at the same time but unknowingly that makes it worse. Meanwhile, you’d have no idea if replacing the fan helped or not.

 

Agreed, by trade im a Stationary Engineer and AC contractor. Moving heat at 12k tons per hr is what i do. To many changes at once make it hard to id what worked best.