Water leaks above tailgate

[SamsBus2012]

Morning all. I recently discovered water getting in above the tailgate so, believing it to be the tailgate seal (old one was made up of bits!) ordered a nice new one and promptly installed - unfortunately problem not cured. Having stripped back the stuck on lining above the tailgate I have identified that the water is coming out of a bodywork overlap adjacent to each top corner of the tailgate opening - photos below.





Obviously this is where the water is coming out but where is it getting in? - The whole high top area internally is bone dry, checked rooflight and window seals - no obvious leaks.
My next thought is two possible sources:
1. The tailgate hinge gaskets (though I think I'm getting a lot of water for that)
2. Leaks at the gutter junction with the high top and running back to the tailgate area (van is parked facing uphill on a slight slope).
I've got some drainage tracing dye so I'm thinking I might place a tiny bit of powder in each gutter (one at a time) and see what happens.
Any further comments or ideas on this would be welcome as ever!
Ta

[SamsBus2012]

Update No. 1
Put some dye in the gutters and, after an afternoon of heavy rain showers, lots of water in the back of the van but no sign of any dye! Loads of water getting in. Aargh! Back to the drawing board!

[lloydy]

i would say it coming in from under the hi top, most if not all seen to rot away under there

[SamsBus2012]

That was my initial thought but as the high top seems to be relatively intact I'm struggling to account for the volume of water that seems to be getting in.
I've got a boroscope at work so I think some exploratory work into the voids might reveal the problem a bit better.

[lloydy]

i hope its not

[CovKid]

Ask 1664 about rot underneath hightops. Almost certainly it'll have to come off and make sure you have someone to hang on to when you see the extent of the rust. Its rarely good news I'm afraid.

[fazzer]

had exactly same problem with mine in the same place but when I removed the rubber seal the top lip was rotton so welded it up and has been fine since.is there anyway to tell if roof is rotton without removing hightop.

[SamsBus2012]

Struggling to see inside voids. Can see some small rust spots but could be far worse down at the gutter line I guess. I've been thinking about how I can look at the roof without removing hitop and I guess the simplest option will be to strip out the internal ply deck and trim - bit of a pain as I only recovered it all a year ago but I think thats the plan. Incidentally the only poor bit on the tailgate seal lip was at the bottom.
So gonna stick a cover over him till I get a bit of time, probably end of month now as off to rugby on saturday and will be on family duty following week as a result. I'll then start opening up inside.

[dbz864]

I had the same problem a few years ago on a komet conversion, I spent ages looking, I never found the problem. Have you tried the grommets, either blanking or with the tailgate cables coming out , visible when tailgate open? If the high-top is sealed all around, I cant see how it can leak! Good luck and let us know if you sort it. Forgot to say its not coming in from rust/pin holes in the steel behind the tailgate seal.

[SamsBus2012]

I think my hightop was made from a komet mould. Noticed tonight that there are no blanking grommets in the actual tailgate but the one on the body is present. There is a complete seal all round on the hightop but this is old and has gone hard so considering replacing with new sikaflex. Might do the hinge gaskets too. There will be a nice tarpaulin over it tomorrow so hopefully I'll get a bit of breathing space.

[dbz864]

yeh I did hinges didn't make any difference, have you looked at the steel (in the hollow) behind the seal, below and behind the seal, very difficult to see . cant see how it could leak at the front and back of high top, as the rain will run off it. mine only did it in the rain I had hoses on it every where, never leaked then only in the rain, it did my head in. Have you a rack or bars on top.?

[CovKid]

There is more than one way water can get in a T25 and it applies to most areas. It can run in, it can be forced in under pressure through gaps (ie by wind/air pressure), and it can be sucked in by capillary action. The latter is the least understood and often overlooked since it tends to occur unseen. Seals themselves start doing the opposite of what they're meant to do - windscreen seals are a prime example of that and the gap needed is incredibly small. Finally, it can accumulate in areas that are completely sealed and then have nowhere to drain, eventually working its way directly through the metal.

Consider all of these and don't presume anything without ruling out each in turn. Either way you'll need to make good both cause and result.

[SamsBus2012]

Roof bars are aftermarket Thule for a high top with gutter mountings - wondering whether the feet have penetrated the seal onto the high-top and I'm getting some capillary action as Covkid suggests. Do you think a small leak at the windscreen seal (which I know I have) could result in water tracking back to the tailgate area when parked on a slight slope? Seems a bit of a long way! I'll park the van the other way around and see if makes a difference. The plan is to start from the top down internally and rule everything out until I hopefully find the culprit(s)!

[CovKid]

No, no route for it that way.

Do you think a small leak at the windscreen seal (which I know I have) could result in water tracking back to the tailgate area when parked on a slight slope?

[mbcamper]

I've got a similar van and I certainly had some leaks before I did extensive repairs. Looking from inside it didn't look too bad, but I was sure something was wrong. I couldn't appreciate the full extent of the rot under the high top until I actually removed it.




Similar story at the front of the van.




It's fixed now, but it wasn't a small job.