Sills

[Butler]

What actually causes the rust on the sills...? dirt crap behind the arch liner...? rubbing between the wing and sill....? And when new wings are fitted how to stop it happening again....?

[19TW80]

I believe the rusting of the wings is caused by a sound-dampening foam insert which VW decided to place on the underside of the wheel arch. The foam insert was retaining moisture, as foam tends to do, and I can only hazard a guess that the untreated/unpainted metal on the underside didn't take kindly to being exposed to damp for long periods, and rusted.

The previous owner of my Ed30 was an encyclopedia when it came to car knowledge, and removed the foam inserts from both sides the day he bought the car, and as it stands there's absolutely no evidence of rusting/bubbling.

I stand corrected, if anyone's got a different suggestion.

[Butler]

What about the sills

[19TW80]

I'd hazard another guess that it's all part and parcel of the dreaded sound-dampening foam insert.

[barelyrelevant]

After recently removing my arch liner and hooking out a small pile of damp dirt which was sitting against the edge of the sill i'd guess that is the problem.

[lukemk5gti]

After recently removing my arch liner and hooking out a small pile of damp dirt which was sitting against the edge of the sill i'd guess that is the problem.

Second that

[MPS]

You'd think a multimillion £ car manufacturer with state of the art R&D facilities wouldn't model in such a f*ck up would you?

Teams of geeks in white coats modelling foam on computers, only for it to rust the wings. Dumb. I think the official fix for this is to trim the foam and then apply a bead of some form of weatherproof automotive specialist sealant [urethane, maybe?] all along the inner sill crease. Thus creating a waterproof seal and rendering it impervious to the elements.

[barelyrelevant]

You'd think a multimillion £ car manufacturer with state of the art R&D facilities wouldn't model in such a f*ck up would you?

Teams of geeks in white coats modelling foam on computers, only for it to rust the wings. Dumb. I think the official fix for this is to trim the foam and then apply a bead of some form of weatherproof automotive specialist sealant [urethane, maybe?] all along the inner sill crease. Thus creating a waterproof seal and rendering it impervious to the elements.

Interesting, one of my arches appears to have this fix but has started to rust through again. I went to VW and they say the paint depth is too deep, I wonder if they have already had the official repair once and have started to go through again!

[pudding]

You'd think a multimillion £ car manufacturer with state of the art R&D facilities wouldn't model in such a f*ck up would you?

Teams of geeks in white coats modelling foam on computers, only for it to rust the wings. Dumb. I think the official fix for this is to trim the foam and then apply a bead of some form of weatherproof automotive specialist sealant [urethane, maybe?] all along the inner sill crease. Thus creating a waterproof seal and rendering it impervious to the elements.

Interesting, one of my arches appears to have this fix but has started to rust through again. I went to VW and they say the paint depth is too deep, I wonder if they have already had the official repair once and have started to go through again!

If VW have it on record the wing was replaced once already under warranty, the paint depth shouldn't be an issue when it comes to a second replacement.  They can't penalize you for adhering to their own rules.

All car makers build in planned obsolescence, whether it be rust or mechanical failures.  They don't want you to keep a car for 10 years. The list f'ck ups on the MK5 is a lengthy one, but it doesn't mean all of us will experience one or more of them.  It's down to luck and/or preventative maintenance.  The latter should be standard on such a complex machine, but so many people resent spending money on cars, and then complain when they break down.

[grey golfster]

I'm With the above guys re the mud n muck behind the arch liners. We Perhaps tend to be lulled into a false sense of security when we see the all-coverring plastic inner arches, and assume that behind them, the car is as new? On older cars, i would have been hosing all this sh1te away on a weekly basis. Rather more time consuming to drop liners.
Owt for Nowt?

For what it's worth, I would also add...

I've just taken delivery of a brand new VW Tiguan.
There are foam inserts in the top of the inner wings, as seen from  inside the engine bay.  Never mind the ones I can't see!
The VW evolution, or "improvement" appears to consist of encapsulating the sound absorbent foam in a plastic bag! 

Manufacturers don't give a sh1t, as long they have your money, and  their liability is discharged.
In the Mk5 example the problem, from their perspective, seems to be the combination of corner cutting design/spec with an over generous corrosion warantee!
Clearly they think that putting the foam in a plastic bag will see out the duration of their liability by warantee?

I would be willing to bet that mk7 Golfs are similar?

Seen this sort of scenario, for years, over all sorts of industrial plant and a wide range of OEMs.

As the man above said, we need to get away from the idea that they want YOUR asset to last

[pudding]

I'm With the above guys re the mud n muck behind the arch liners. We Perhaps tend to be lulled into a false sense of security when we see the all-coverring plastic inner arches, and assume that behind them, the car is as new? On older cars, i would have been hosing all this sh1te away on a weekly basis. Rather more time consuming to drop liners.
Owt for Nowt?

For what it's worth, I would also add...

I've just taken delivery of a brand new VW Tiguan.
There are foam inserts in the top of the inner wings, as seen from  inside the engine bay.  Never mind the ones I can't see!
The VW evolution, or "improvement" appears to consist of encapsulating the sound absorbent foam in a plastic bag! 

Manufacturers don't give a sh1t, as long they have your money, and  their liability is discharged.
In the Mk5 example the problem, from their perspective, seems to be the combination of corner cutting design/spec with an over generous corrosion warantee!
Clearly they think that putting the foam in a plastic bag will see out the duration of their liability by warantee?

I would be willing to bet that mk7 Golfs are similar?

Seen this sort of scenario, for years, over all sorts of industrial plant and a wide range of OEMs.

As the man above said, we need to get away from the idea that they want YOUR asset to last

The foam in a bag thing I'm pretty sure is to stop rubbing / squeaking noises and also to prevent the foam absorbing water, which would cause condensation and smells in the cabin.

Back in my Corrado days, they used a different type of foam which wasn't bagged, and waaaaaaay denser and better quality.  So you're right, big cost cuttings going on at VW, but those savings aren't passed onto the customer obviously.

Blame the financial director who joined VW mid way into the MK6 product lifecycle,  can't remember his name but he questioned why it took 7 times longer to make a Golf than a Focus.  Since then, they've been simplifying the build.....and yep, watched loads of VAG videos on YouTube and the MK7 appears to be just as badly made.  They're just too new to have developed rattles yet.

Thing is though, if we defect to BMW, Mercedes, or Ford, or who ever, it'll be the same schitt, just different clothes on the outside.   Better the devil you know sometimes!