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Thu 29 Dec 2005 09:52

VW Mk III Golf VR6 Highline: cap on cat - Roger Jones

No-one on the VR6 forum could explain this feature precisely, so I thought I'd ask here.

I've just replaced the screw cap (19mm hex nut) at the back of the cat on the offside. The old one had disintegrated and exhaust fumes were therefore venting, which would have been an MOT failure item. The cat is perfectly sound, but the screw cap must be made of inferior stuff.

Why is it there? Does something else screw into that hole on cars destined for non-UK markets? Or is it simply a hole for a testing/measurement device?

Does anyone know the correct torque setting for it?

By the way, Wayside parts dept (St Albans) couldn't find the cap on their exploded diagrams and a whole-cat replacement nightmare started stirring in my mind. However, my mechanic managed to source it via M. J. Warner at Hare Street, nr Buntingford, Herts.

Part numbers:
* screw cap for cat converter 4A0 131 737 A -- "cap nut"
* washer N 013 830 2 -- "seal"

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Thu 29 Dec 2005 10:21

VW Mk III Golf VR6 Highline: cap on cat - Andrew Moorey (Tune-Up)

Its for the second Lambda sensor (post cat)which senses the O2 content of the gases leaving the cat to ensure the cat is working correctly.
Andrew

--
Simplicate and add lightness!!

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Thu 29 Dec 2005 10:44

VW Mk III Golf VR6 Highline: cap on cat - Roger Jones

Thanks, Andrew. So it's an optional permanent fixture or for temporary test equipment? I guess the latter, but you will know.

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Thu 29 Dec 2005 13:10

VW Mk III Golf VR6 Highline: cap on cat - jc

Some German and Swedish market cars used the hole for a sample pipe to check cat operation.If I remeber rightly the hole has the same thread as a spark plug tho' I can't remember which one as we have used them in the past to blank these holes.

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