VW Trident: Is there a leak under the carpet?

Well, I finally admitted defeat and took it into VW Vans Norwich. They reckon the leak is due to a worn runner under the sliding window above the sink. That'll be £700 sir for a whole new window unit. I hope they're right!

...I find it hard to believe that the sliding window has been used so much that it's worn out the runner !

The factory sliding windows are notorious for leaking - mine did so from new - but I'm a bit surprised you saw no evidence internally.

Anyway, if you take a look at the coverage that the subject has on the VWT4forum, you'll see that typical causes are worn/damaged seals and blocked drainage channels - I can't recall "worn runners" ever being a cause. If it were mine I would be sorely tempted to follow one of the how-to guides on sealing it up for good, unless you use it frequently. It does depend though how much cooking you do and whether leaving the side door partly open is enough ventilation...

Sorry to be so blunt Steve but I think the worn channel theory is codswallop. You will recall that I pointed you in the direction of an offside window earlier. My T5 is two years older than yours and I can see no sign of wear in the channel/runner. It would need a great deal of work to have any significant wear effect.
Our problem was a failure to close the window properly due to debris in the channel, particularly the upright channel at the forward end. Two further suggestions. I am fairly sure there is a small drainage hole to the outside from this channel. It's too dark to check ! And second, the window seal is completed by pressure against rubber strips in the frame which depends on the window being fully engaged in the closed position.
It would take a lot to persuade me to spend £700 without exploring every conceivable alternative. Best of luck with this.
Keith

Before I parted with that sort of money I would need to be absolutely sure that it would cure the problem. I would gaffer tape all around the window seals & joints, then check if the water leak dried up.
Is the window like the T4. ie. old type sliding with rubber seals or the later bonded in place type?
If it's the bonded type you can get much, much cheaper replacement glass as long as it matches the originals.

finbar

Steve.  I checked what I had written in the previous statement in daylight. My memory was not at fault. There is a small drainage hole at the forward end of the channel. I put water in the channel and it drained out from the lower edge.  Is yours blocked? Also, the weather seal is a rubber tube-like strip but it is in a groove around the outside edge of the sliding glass and not in the frame as I thought. If this is damaged it would let in too much for the drain to cope.
Keith

Thank you, Keith and others for your interest and most helpful comments and trouble on my behalf. Well! Bless my soul! I was well heading that way but, with Keith's encouragement too, I was well signed up to the Codswallop theory. But today I managed to get back in to the Norwich VW van centre. And, guess what? They seem to be correct.
Although the window operates perfectly normally and appears perfectly OK, on close inspection the sliding part is 2 or 3mm out of square. Nothing visible is broken or looks out of true, but clearly something is and this is enough for the rubber seal not to work correctly. VW have assured me it is the source of the leak, even though no water manifests itself inside the van until the strangely restricted wet patch in the carpet between the two front seat-backs. I do need the window to keep opening (I use the van for my bird photography), so have bitten the bullet and they are fitting me a whole new window unit for close on £700 (five hundred and something plus 20% VAT). Oh well! Apparently the new unit will have a two year guarantee. Thanks again all for your interest and helpful comments throughout.

C'est la vie !

Just to add to the pot. I found this thread on the VW Cali forum. It does seem like the sliding window is a known problem and a lot do have the complete window replaced.
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finbar

Thank you again, Finbar for coming up with that. I wish I had found it myself at the beginning, but it is still good to know now. It is exactly my problem, though I still would have been surprised that the water only manifested itself inside as a wet patch in the carpet between the two front seatbacks, and nowhere near the offending window. But I can report that VW Norwich's replacement of my entire window has cured my wet carpet. Hooray! However, having read this new thread I am less than impressed that I did not necessarily have to have a whole window unit at all, as VW Norwich insisted. Furthermore they quoted me a 'total all in' price of an outrageous £720, but when I came to collect the van it was £820! Still, one expects VW to be cheats nowadays especially. It was rather a lot though when a blob of vaseline might have done the job!