How does fording cable work?

[w30bob]

Hi Guys,

When I got my M a few months ago it didn't have a fording control in the dash. I've been looking around at pics and reading the manuals to try to understand what the fording control in the dash actually controls. All the fording cables I've seen for sale on eBay and such have the control handle operating two cables. One cable opens and closes the fording valve that controls the PCV valve operation.....I understand that part. But what does the second cable control ? Any pics would also be greatly appreciated.

thanks,
bob

[w30bob]

Ok........after a bit more digging and checking out pics it looks like the second cable goes to another fording valve located in a pipe that runs from the tube that connects the carb to the manifold. Not sure what the function is here.........so if anyone knows can you tell me what this valve is doing?

thanks,
bob

[52 M-42]

The valve under the manifold is called a Donaldson valve. It controls pressure inside the engine so that water doesn't leak in while you are fording. YOU NEVER WANT TO CLOSE THIS VALVE WHEN YOU ARE NOT FORDING!!!!! It will over pressure the engine and you will have leaks everywhere. If you go to the following link you will find copies of the old PS Magazines. You can search for info on the Donaldson valves which will explain their function in much more detail.

http://dig.library.vcu.edu/cdm/landingp ... ection/psm

Hope this helps!

52 M-42

[ODUSAOK]

Hi Bob,
As you wrote the one cable controls the valve to the PCV line under the manifolds.The second cable controls the valve at the air cleaner to carb elbowwhere the oiler filler pipe vent line connects.With these two valves/lines closed,the blow-by gasses from combution leaking past the piston rings begin to seep into the crankcase with no way to escape/vent.When the motor is subject to water immersion during fording,this is a positive situation.The seeping gases pressurize the cranckcase(positive pressure)and the water is prevented from coming in all the very small openings that would otherwise allow water to enter the motor.It has to be remembered that,even if there was absolutely no leakage of oil to the outside of the motor(and most of these old technology engineered blocks do leak somewhat)all of the lipped seals are designed to hold liquid(oil) INSIDE the motor.Liquid(water when fording)on the outside of the motor is not prevented by the seals from entering the block even at a very low pressure.The positive pressure building inside the block is what actually seals the engine.The previous reply,(with the link to P.S. magazine that I will check out,Thank you sir.)is right on the money.Unless those valves are opened in due time,the positive pressure will eventually force oil out all the openings it kept water from coming in at.Very messy at the least.LIke most things in life it's a double edged sword.Great to have in the water,terrible to have any longer than necessary.I hope this too helps.Chris

[Paul in Kempner, TX]

TM 9-8030, May 1955, Paragraph 68.c. Deep Water Fording refers to TM 9-2853 for instructions on vehicles equipped with deep fording kits. Do you have a deep fording kit? If so, do you have TM 9-2853?

TM 9-2320-212-10 Operator's Manual (30 November 1973) is an update to TM 9-8030 and refers to TM 9-238 (October 1961) for Deep Water Fording of Ordnance Materiel.

These "fording" manuals are two references I do not have because I never planned to use a deep fording kit. I'm sorry but, without a correct reference I cannot give you a correct answer. Maybe these TM's will answer your question.

[w30bob]

Hi Guys,

Great info....thanks!! Paul, I don't have the "deep" fording kit, which I assume consists of the brackets and pipe for the exhaust to route it up to the cab height, and the intake hose and pipe that goes alongside the windshield. My M did come with the fording air cleaner and control on the dash, but I think that stuff was included on all M37s and then you had to install the "deep" fording kit when you needed it.

thanks,
bob