oh i see your point it seems like it would be such a small difference though.im not claiming to be an expert at this stuff but i see your point,but just doesnt seem like enough to matter.experiment time!!!

 

I see it now, thanks for the picture.

So to sum up my choices: 1) get a new fan clutch, 2) see if I can get the existing fan to lock up, and 3) Remove the t-stat. correct?

Villahermosa is the last big city before I cross the jungle of the southern Yucatan and I don't want to break down there. So I need to get this done here.

Thanks everyone

 

Yah, I'd say those are the options you have indeed, in the preferred desired order too. Just so you know tho, the fan clutch is pretty expensive, kinda why I came up with that contraption of mine.

 

I had to replace mine last year. I don't know why it went out so quickly. They are expensive.

 

This thread is shows how messed up some people's trucks really are. I am not against doing stuff to get a vehicle running, but having to run your truck with no thermostat, the fan bolted together, and blankets on the radiator has got to tell you something is wrong. When International and Ford got together and designed these engines and everything else that goes along with them to fit in these trucks, they were designed to pull all day long WITH a thermostat, and WITH a fan that the clutch works.

If your fan broke and you want to run it with it locked, that's fine. If the thermostat stuck, and you want to run it without one all the time, that's fine too. But I would not recommend these methods as a permanent repair for someone, or say "that's what you have to do to these engines or they overheat"

From what little I have learned so far about these engines, too much fuel will cause them to heat up. If you are getting black smoke, that sounds it's getting too much fuel too me for some reason.

 

No argument there. I'm running mine without a fan at all! (DISCLAIMER: I am not towing and its winter right now, so do this mod at your own risk)

Normally these engines cool very well.

 

I know this seems trivial but have you checked the radiator cap? Cooling systems require a certain amount of pressure in the radiator or they don't function correctly. If the cap goes to crap then sometimes you can end up with bizarre cooling symptoms.

Really crude way to check is to attempt to crack the cap when it is warmed up, but it can be dangerous as hell if you do it wrong...

I will but a disclaimer that I don't have any experience with this in the 6.9

 

I can say I have seen the no thermostat trick work both ways.
I have seen that trick make it impossible to drive the vehicle without it overheating and also I have seen it make the engine never warm up.

A lot of that has to do with the radiator size in relation to engine size.

M.S.L.C. your braces are going from the water pump pulley bolts to the fan blades if I am thinking right.

 

Yes they are, and oddly enough with them the engine runs a whole lot smoother than without them (I'd imagine the fan clutch was vibrating on the shaft before).

And now, I don't recommend to anyone to install these instead of a good clutch, problem in my case is that I have like $400 in my bank account and a clutch is over $150 - whenever I can afford anything more than just food and gas I'll make sure to change it, but for now the braces work. Also, FWIW, the grille blanket is there for the massive trans cooler, without it I don't think the trans fluid will ever warm up on the freeway. The radiator block-off plates were installed while I still had no braces and the clutch was slipping, when I got on the freeway the radiator would run pretty cool from just the airflow pushed through it - the fan braces are there just to ensure that if I get stuck on the road (be it cause of an accedent cleaup, or just heavy traffic, both very common situations roujnd here) I can idle my engine for a whole day without worrying about overheating it. And I agree with you on the fuel setting, however I only get black smoke when acceleraring in OD with the engine speed under 1400rpms, once I'm up above that there's not even a hint of smoke, hills or no hills. I average around 18mpg now on the freeway running at 2k rpms and 60mph, so I don't think I'm burning too much.

 

I have only heard one explanation of this through the years that actually made sense. I hear the "coolant traveling too fast" theory, and I just don't believe it. In my mind, that just doesn't seem have any good logic behind it, especially when the emissions engines came along and the factory put a smaller water pump pulley on them to pump more coolant to keep them cool.

This is the only explanation I have heard so far, that I believe.

This one says it's a pressure problem with the pump when no thermostat is installed. Like any pump, a waterpump on a engine will have a pressure differential, with high pressure on the output, and low pressure on the input. The high pressure on the output of the pump is going to be developed at the first restriction it hits. On most all vehicles, this is the thermostat. If you take the thermostat out, this moves the top of the radiator wide open to the output of the pump. This moves the output pressure of the pump right onto the bottom of the radiator cap, and the "overheating" you are seeing is actually just the radiator cap being forced open by the pressure of the waterpump. They say if you want to run without a thermostat, the best way to do it is to take a old thermostat and cut the guts out of it, making it basically a big washer. This will restrict the flow enough for the waterpump pressure head to be behind the thermostat, and not up against the radiator cap.

 

I would think if your fan clutch was bad, then your engine would be overheating in traffic with the ac on. At highway speeds, ram air is cooling your radiator more that the fan is anyway. My friends truck is doing the same thing over heating on the highway. His is a retired u haul with the van body on it. At one point the idiot light came on for water temp. If you back out of it, the temp goes down. At idle, the temp runs at 180. I installed an aftermarket temp gauge in two different places and it is still getting up to 240 at the most on hills. So, i think it is a fuel problem or radiator, but you said you had your radiator rodded out, so i dont know now.

 

The pressure in the cooling system is caused by heat, not by the water pump. While there might be a small pressure difference between the input and output of the water pump, it is very little compared to the system pressure at 200 deg. Keeping pressure on the system raises the boiling point of the fluid.

Coolant overflow happens because the pressure (from heat) causes fluid expansion in the system, overcoming cap pressure. Even under normal operation, this will happen. If there is a failure such as a head gasket leak, (high pressure combustion) or a stuck t-stat, it will cause the cap to relieve too early. This will also happen if the cap is weak.

If you were to place temp probes throughout the engine block and heads, you would find that constantly moving fluid does not remove as much heat from vital areas like fluid that is regulated. You will find that the fluid itself is cooler, but those components being much hotter.

Jason

 

Who says the guage is right, aren't Ford temperature guages famous for being wrong. Is the radiator boiling over? Is it too hot for you to touch?
You may be having other problems.

 

Are you running a NA 6.9? If so you have 160- 170 HP. You have a truck with a camper and pulling 8000 lbs. These engines are notorious for being slow and weak. My NA (I was told it was a 7.3,( but after Dave S. told me how to look at the engine number, it is a 6.9) is very weak. I have tall gearing, but I have to downshift on the slightest grade. When I'm on the slightest grade, the smoke rolls. Thats why I'm installing a turbo on it. Make sure you are not running out of power and looking at a faulty guage. What happens when you slow down, does it still run hot

 

Pull the spring out of the front of the fan clutch and turn it all the way. I can't remeber wich way. If you turn it the right way it will lock the clutch so you can get home.