GMC Fuild Drive Fans

[Mrbill4108]

Hi everyone,

Have a question about the fluid drive fans (Torus Drive) installed in GMC 4106's and maybe others. 

My 4108 has one installed in it and I'm not sure I understand how it works. So here is my main question. 
What is the oil flow path for the fan since 4108 didn't come with it (at least my books don't show it). 

Mine is hooked up like this:
Pressurized oil comes from the block to a tank mounted over rear sway bar. 
From the tank it goes to a TEE in the oil pan from there it goes to the thermo-valve then to the fan housing. 

So my big question: Is the oil line going to the fan suppose to be pressurized or a return line?  This is why I'd like a flow diagram for the oil.

If the line is a return line then where does the fan get its oil from?

The fan seems to work at this time but I'd like to know more about how it works. 

Thanks,

Mrbill4108

[JackConrad]

I don't remember which way the oil flows, but I do remember that when I installed a new torus drive assembly, I put the gasket on backwards (blocking an oil passage) and the bus immediately overheated on my test run. So oil does flow through a passage between the block and the torus drive, This is probably the supply (pressure) side and the line going to a tee at the pan is probably the return. It has been quite a few years since we had our "06, and my memory isn't quite as good as it once was.  Maybe a current '06 owner can firm or correct this.  Jack

[Sammy]

I'm looking at a service manual for a GM transit bus from 1973. It says to find a "Hydraulic Fluid Drive Fan" manual - it will tell you how it works,how to repair it,etc.
I remember working with them back in 1985, there were still some transit buses running with them - Fishbowls and Flxibles. We used to put a bolt in the oil line at the vernitherm valve to restrict engine oil to the torus as a temp repair to let engine produce more heat in the winter. Fan would not spin at full speed when line was restricted.
The Torus works like a transmission torque converter, more fluid that fills it creates a stronger fluid connection between the engine and the fan.The vernitherm valve is a temp controlled valve that mounted in the coolant pipe. There was an oil line feeding engine oil it and another line to the torus.
When the engine is cold, the vernitherm valve would remain closed, not letting engine oil feed to the torus, therefore the fan would free spin. As the engine got to operating temp, the vernitherm valve opened gradually, letting fluid (engine oil) fill the torus, creating hydraulic locking - torque converter theory.
I have converted this setup to a belt driven style a few times.I used the parts from an RTS application.
Hope this may help you.
Sammy 

[Mrbill4108]

Thanks for the info guys this has helped a lot.

So to sum up, the valve should have pressurized oil on the input side, then open when engine coolant gets hot (around 180 degrees) and allow the oil to fill the fan cavity to drive the fan.   

Does anybody know if the valve allows some oil to pass all the time to keep the bearings in the auxiliary drive lubricated or does it close completely when cooling is not needed?

My fan has never really spun that fast, even when the engine was hot / warmed up, guess because it does not really get pressurized oil just the left over that didn't go back into the pan.  So guess its time to replumb.

Thanks again for all the help,

Mrbill4108

[LUKE at US COACH]

Hi Mr. Bill:

Your fan torus is bolted directly to the engine oil pump.
The vernitherm valve allows oil to pass through the torus.
As the engine temp rises, the valve (if operating correctly, closes, holds
oil back into the Torus and the fan spins faster.

Now, if coach heat is not important, then the vernitherm valve can be bypassed, and your fan will spin at full speed from the time you start your coach, if the torus is in good shape.

You can call me toll free tomorrow at: 1-888-262-2434 or E-Mail me at: uscoch@att.net if you need additional heolp.

I Hope this HELPS!!!

Hapy & SAFE!! Bussin' to Al.

LUKE at US COACH