Engineering for fording capabilities

[Boatcarpenter]

So my question is, how is the multifuel engine designed and built to be able to withstand running at say 200 degrees with an exhaust manifold temp significantly higher and then be driven into 50 degree water for fording and not suffer serious immediate differing contraction rates of the various parts due to being made of different metals with various coefficients of expansion? I realize gaskets come into play here probably and the mass of the engine helps it cool at a slower rate, but still, it seems as though the difference in temps would be quite a shock to everything.

Just wondering
BC

 

[Westech]

that is a very good point, I would think there is a TM about how to enter water. (like idle to cool down first) Bj would be the guy to talk to about that. im sure he will put in his 2 cents here.

 

[ken]

I've forded with my truck many times. Espacilly when it belonged to the FD. I've had in water over the hood a few times with no problems. But the generator will quit after about a hour under water. It's funny to see the temp guage slam to the left when it hits the water. The fan is pretty tough to be able to hit the water. The noise from the fan is pretty wild untill it's completely under. It sprays pretty far if you have a side cover down.

 

[cranetruck]

Okay, since John Wayne ( ) here thinks I should toss my two cents worth into the discussion, I will say that a lot of times the water temp can be warmer than the air temp. In the winter, for example, the water will be no colder than about 32F while the air temp could be a lot cooler.


Also, most water crossings only last 30 seconds to a minute, so there is hardly enough time for the internals of the engine to notice. Kind of like hosing it down with a garden hose, but more even.

 

[Recovry4x4]

Hey Bjorn, your data plate and pump plug are on the way. I tossed in 2 little wiring doodads, tell me what you think.

 

[rmgill]

Bjorn, but water has a much higher capacity for heat even if warmer than ambient air. So heat is still going to be taken away from the engine in higher quantities. And if it makes a state change, even more heat is taken away as it's now steam.

 

[cranetruck]

Thanks Kenny!

I agree Ryan, but it is for a very short time period and the fan stops doing its job, so there may be a small tradeoff too.
The coolant will help keep the engine warm also.
The only parts that may be above the boiling point of water are the exhaust related ones and they swing from a few hundred degrees to a thousand or more every time the accelerator is depressed.
Cast iron parts will expand and contract together.
On the highway I have seen the engine temp drop 40 or more degrees going down a long hill/mountain (that's the reason for my custom radiator cover, BTW) in less than a minute.
Put a sensitive thermocouple probe next to the engine temp sending unit, there is a plug there, and look at the temp changes on a DVM. You'd be surprised how much and quickly it changes.
Perhaps I'll do the fording experiment over one day with more water and look at some details like this.

Look around, it's very hard to find a place to ford your truck, so this is probably not a critical issue for most of us anyway.

Aside from the engine, the warm air in the axle housings will cool off and there may be some condensation because of this. The breather valves are essentially one-way valves designed to let expanding air out. When the air cools it contracts and fights the breather valves. My solution here was to extend the vents to a central point under the hood high on the fire wall. They can also be pressurized.

It's an iteresting question and I don't have any specific answeres at the moment other than the general ones stated.

 

[ken]

I think bjorn's right, they were only intended to get wet for a short period of time. I had to keep it under water for hours doing deep water rescues. The water was about hood deep on the freeway and we were picking up people standing on the roof of thier cars. The turbo and exaust was under water many times. Each time the engine hit the water the temp guage went back to cold quickly. Untill the electrics quit. Water entered EVERYTHING that could hold water. I had to flush the brakes, winch, steering box, fuel tank, tranny, t-case, and all the axles. I even had water in the headlights! If you ever take your truck swimming you will need to clean and repack the wheel bearings also. I use marine/boat trailor grease in the wheelbearings and all grease fittings.