Thread: Oil Leak 3.0L D4 - Oil cooler and filter assembly -should it have a hole here!

You can see the hole at about 20 seconds in.

Still baffles me at this point what the hole in question in the body is for...

Here's mine, bit of crud in the bottom of the recess, but no oil leak. Thinking about it a bit more, i think this hole is part of the upper housing casting riser or release, i.e. somewhere to lift the casting out of the mould once cooled. So the oil must come from the cooler/heat exchanger underneath if thats failed or cracked somewhere or the seals themselves.

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The oil on the left hand side is from the drivers side y piece throttle body to manifold seal.

On a couple of cars and bikes I’ve owned, there have been ‘witness holes’ to indicate an internal leak (usually a seal) of oil or coolant.
My current bike has one on the side of the block to indicate a water pump seal leak (pump is internal).
I suspect that the one in this discussion is for an internal oil seal of some description.

Originally Posted by Hugh Jars

On a couple of cars and bikes I’ve owned, there have been ‘witness holes’ to indicate an internal leak (usually a seal) of oil or coolant.
My current bike has one on the side of the block to indicate a water pump seal leak (pump is internal).
I suspect that the one in this discussion is for an internal oil seal of some description.

Makes sense. So via the tell-tale you can see whether you’ve got a leak on the oil or coolant side of the cooler.

If it's the same as the 4.4's cooler then the top gasket seals both oil and coolant. I suspect that if the hole is a witness hole then it is used to check if the gasket between the housing and the cooler is leaking as it could be difficult to determine whether oil is emerging from the upper gasket or from the seals underneath the cooler.

Ordered a couple of these weird seals that seal the oil air separator and block. I don’t think they’re leaking but figured while I had it all apart I’d try and change them. I say try as I suspect they’re going to be a real pain to extract as they are metal body with rubber seal so I predict they’ll be wedged in super tight.

And after all this I still suspect it’s the cam seals on the rear not the cooler, but as I can’t explain the oil in the V I’ll do it all anyway.