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Oils are not always Oils ---

1082 Views 6 Replies 5 Participants Last post by  13Tregex
How I found out there are (at least) two different Oil Filters on a V6 TDI

I had this great idea on how to modify the Oil Filtration system on my V6 TDI and it involved fitting a braided hose to the cover of the Oil Filter housing. Rather than muck around with my existing filter assembly, I decided to buy another from a wrecker (breaker) and use that as a prototype/test-bed unit.

So of to Ebay and purchased a used Mahle Filter Assembly for a Touareg/Q7/Cayenne and it arrived 5 days later from Germany. Excellent service.

Well now the fun begins, as although this unit is identical in every aspect, except for ONE! I now find there are two types of Mahle Filter Assemblies, mind you they both bare the same product code and item numbers.

The first type, as fitted to my Touareg, uses a square section seal between the body and the cap, and the alternate uses an “O” ring seal, and they appear not to be interchangeable. BUGGER! So much for my prototyping..back to the drawing board, as I don't feel like buying another and risk have two useless spare parts.

Below are a couple of photos to show the difference. If anybody wants a spare they are welcome for the cost of the postage....



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There is no difference in the sealing of the filter housing using the square 0-ring or the round o-ring. They both will seal. Round o-rings are used in hydraulic system for umpteen years as the square type up to 3000 psi. Square o-rings are usually used on applications where there is a bit of debris present on the sealing surface. Round o-rings are usually used in a more universal application, with ease of assembly, service comes into play. Housing tolerances will also come into play. The pressure is low enough in engine where a softer seal will seal better
Materials will also make a difference. Buna, viton, carbon, polyurethane, silicon, etc...
I guess, what I am trying to say is that, if the filter housing and associated seal is used in the filter receptacle, then it will seal exactly the same.
This may be true of the filter fits discussed here, however it is certainly not true of the hydraulic systems alluded to, especially the DIN from Europe, and specifically Germany. The hydraulic systems are designed up to 360 Bar for either a square O ring, or a round O ring depending on application and design. They are not interchangeable in those applications.
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