Mk II Oil Cooler Internals

HolyCat

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Here are some photos of the spring and valve/plug assembly which originally came installed in the Mk II oil coolers. These photos were graciously taken by mr55s (Brian). In each of the four photos, 1. Is used to identify the drain plug and washer, 2. identifies the spring, and 3. shows the valve/plug.

Photo 4 shows how all the parts fit together inside the “leg” of the oil cooler. The valve/plug fits on top of the spring, which rests against the drain plug. The flat part of the valve/plug is away from the spring. The oil cooler on my car is missing the valve/plug and spring and this is the first I time I have seen what they look like.

Originally, I thought that this assembly was used to block flow through the oil cooler until the oil warmed up. Without ever seeing the parts, I had assumed that it acted like a thermostat and the spring would warm up, get longer, and would move the valve/plug to come off a seat and allow oil to flow through either all or part of the cooler.

Having seen photos of these parts, it appears that the spring and valve/plug operate on the basis of pressure. For the assembly to act as a thermostat, the valve/plug would have to come off a seat as the spring expanded. This would mean the seat would have to be on the underside of the valve/plug. But there does not appear to be insufficient surface on the underside of the valve/plug to mate up with a seat. Furthermore, it would mean that the valve/plug would have to sit above the seat, but then it would be impossible for anyone to put it in or take it out.

It would appear that the flat top of the valve/plug probably seals against some overhead seat inside the oil cooler. It may be a one-way (check) valve that allows oil to flow down past the valve/plug and spring into the rest of the cooler and stops oil from flowing in the opposite direction. Or it might be a pressure relief valve and only opens up when the oil pressure is high enough to overcome the spring pressure. Both these scenarios presuppose that the top surface of the valve/plug is pressed against the seat inside the oil cooler when the drain plug is installed and tightened.

However, there is another possible scenario. Perhaps the valve/plug does not seal against the seat when installed. If so, then as the spring heats up and expands, then the valve/plug might then seal against the seat, cutting of the flow of oil. But this would not make any sense, as you would expect that you want the oil to flow through the cooler when it gets up to temperature.

So, does anyone out there know exactly what is the purpose of this assembly and how it works?

Photo 1 - The parts laid side by side, showing bottom side of valve/plug
Photo 2 - The parts laid side by side, showing top side of valve/plug
Photo 3 - The parts laid out in the order they are assembled in the oil cooler
Photo 4 - The parts stacked the way they fit into the oil cooler
 

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Fordlandia

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My theory...

I think you are right, but someone has to know the answer "for sure." I think it is a pressure activated mechanism. If pressure on the input side (driver's side on US cars) increases to a certain level... the "tube" running along the bottom acts as a "bypass" tube... enabling some of the oil to flow without going through the cooler. Under normal operating pressure, most (if not all) of the oil goes through the cooler.

I could be wrong. Wouldn't be the first time.
 

norm1

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I think you are right, but someone has to know the answer "for sure." I think it is a pressure activated mechanism. If pressure on the input side (driver's side on US cars) increases to a certain level... the "tube" running along the bottom acts as a "bypass" tube... enabling some of the oil to flow without going through the cooler. Under normal operating pressure, most (if not all) of the oil goes through the cooler.

I could be wrong. Wouldn't be the first time.

Sounds right.

I have to go out and pull mine apart. I may have a missing spring....
 
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