Tdi cartridge oil filter is a badly flawed design.

[mk2]

Just changed the oil and filter on a Tdi (AMF engine code), and have noticed that any filtered out crud manages to get into the clean oil feed pipe, every time you change a filter. It's the oil filter system used on most newer vdubs across the range. Basically when you lift it out, it's meant to drain everything into the sump (and out).

But it doesn't.

The filter seal between the clean (inside) and the gunged outside releases a few mm before the central sump drain opens. Which means as the plastic cap/filter holder is uscrewed and is slowly lifted as you release it, all the gunge flows into the clean oil feed. And there is no way of preventing it or removing the crud. Not good. I'm pretty sure it's not meant to work like that, but I dunno...

Means every time you change the oil filter, you introduce filth into the filtered oil gallery that really and truly is meant to stay clean. 

Thoughts anyone? Am i missing something?

The way its meant to work is described in the VW self study guide, but from what I've seen and my experiments, it doesn't work like that.

[tigcraft]

That’s rather an interesting point. Not even serviced mine since I’ve had it but I’ll study it nearer the time. 

[mk2]

@RAB, what do you think? I know it's the same on a 3L.

[RAB]

On 12/26/2021 at 10:20 PM, mk2 said:

@RAB, what do you think? I know it's the same on a 3L.

There shouldn't be any crud directly under the filter, only at the sides, so how does it enter the outlet? The filter is only intended to filter out fine particles which should be retained by the filter. Anything else should stay in the sump. That's why you should always remove oil by removing the sump plug, not (as VW do) by pumping it out.

RAB

 

[mk2]

What I find is that the whole filter containment system stays full of oil (like it's meant to) until you start unscrewing the cap. Then the moment air gets in via the cap thread, the outside contaminated oil along with 'some' detritus starts flowing down between the base of the filter cartridge and the centre- because the centre is still sealed by that little extended plastic plug with the O ring. The dirty contaminated oil can't get into the sump just yet (still sealed), so it flows under gravity into the clean side for a few seconds, until you actually lift off the cap and filter, opening up the sump channel.

I only discovered this because there was a particle of gasket/sealant/carbon or something sitting in the clean feed gallery and I wondered how it had got there (as I'm quite meticulous when I work). I sucked out what I could with my suction pump and only then did it become obvious where the problem was. Poor design. I'm really not impressed at all. I prefer the vertical mounted/hung metal clad disposable cartridges any day.