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V40 D4 Oil filter housing leaks

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Old Feb 19th, 2021, 12:58   #1
DavidKnight
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Last Online: Oct 19th, 2021 08:35
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Location: Bournemouth
Unhappy V40 D4 Oil filter housing leaks

Does anyone have any advice to give on this:

The filter housing has an end cap which is supposed to be tightened to only 25nm. Recently we had a simple oil and filter change done; and the engineer massively overtightened the cap housing causing a hairline crack, which caused a huge oil leak.

Fortunately, the company [who shall remain nameless] did the right thing and came out to rectify; which took a bit of doing as they needed parts etc; but that is now completed; and the housing cap replaced, and tightened to 25nm.

However, oil keeps weeping from the thread of the end cap; just enough to be annoying.

How can we stop this? What is the likely cause?
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Old Feb 20th, 2021, 15:09   #2
DavidKnight
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Angry Update...

Said company has now been back out to have a look; and tried doing the whole job over again [3rd time].

Started up: oil pouring out from the thread area!

Engineer not at all happy, and takes the cap off again to have a look at the gaskets. Seems as though structurally, the housing has a male, threaded top ending in a lip upon which the female 'cap' screws on and tightens to the specified 25nm, no more. Now, inside the cap at the end of the female thread is a shoulder/crevice, into which a square section circular gasket sits which is part of the filter replacement kit. This is the primary pressure seal which 'mates' to the circular lip at the top of the housing threaded area.

Therefore, it is critical that lip is not damaged, otherwise it will not form a good high pressure seal. This acts as the primary oil retention since any oil would have to get past that, find it way down the screw threads [of which there are quite a number of turns] to the end of the cap where it meets the filter housing; where [no surprise] there is a secondary, very fine o-ring which acts as a secondary oil seal in the [supposedly] unlikely event oil would get past the primary seal. [I do NOT think this o-ring is part of a filter kit, btw]

The engineering tolerances relating the depth of the respective threads and the ability for the filter housing lip to mate with the primary oil seal in the cap's shoulder, plus the secondary oil seal at the housing end; are very tight; which is why only 25nm of torque is required. The point being: make the primary seal seat correctly; which should neatly also seal gently against the secondary seal.

But what if something is wrong with that primary seal? What if it leaks, and the secondary seal cannot cope, since it was never designed to hold back full oil pressure? Naturally, the response would be to tighten the cap a bit so the secondary seal is held more tightly closed; right? Which would likely stop the leak temporarily.

Well, if you do; this will also have the effect of placing far too much strain on the female lip of the housing; it's mating with the primary seal, and in my case; caused not one, but two 3-4mm square chunks of plastic to crack off from the lip; thus making a seal impossible no matter how much one may tighten the cap! The chunks looked like they were supposed to be there are they appeared almost square, like notches.

This was only noticed by the engineer when I ran my finger around the oil-soaked lip and asked him if the gasket had matching, mating rubber lugs to sit into the notches and effect a seal. Only then did he use a gentle probe to clear away gunk and oil and realised the 'notches' were in fact broken parts of the filter housing lip.

It seems as though the sequence of events leading up to this was the cap was over-tightened in the first place, possibly because the primary gasket was not seated properly and the engineer noticed the oil leak, which stopped when over-tightening the cap. Problem 'solved' or so he thought; except that doing so damaged the internals, which then let go under normal driving conditions and caused a high pressure oil leak.

Subsequent efforts to correct the problem lead to a cascade of errors including the destruction of the cap when attempting to remove it from it's over-tightened state; not noticing the notches in the lip; etc etc.

Now we are waiting upon a replacement oil filter housing.
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