A Mystery Is Finally Solved, With A Question (1 Viewer)

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DanielFord

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Jun 1, 2013
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Whenever we park our van with the rear end sloping downhill, in heavy rain water leaks in through the air con unit. When we park 'nose' down the water doesn't come in. This has baffled me for many months, and have usually just parked with the nose down.

This weekend, we were parked rear down, and through the night it absolutely poured with rain, at about 4 in the morning I was awoken by the familiar dripping sound. Sure enough, water coming in through the aircon unit. This time however, I removed the roof unit inside, and discovered that the water is not actually coming in through the aircon unit, water is coming in somewhere else, and the first drainage point in the van is the aircon unit.

Been up on the roof, and the most obvious culprit is the bathroom roof light. It has been badly sealed at some point in its life, with loads of excess sealant squeezing out. This also would explain why the thing is so damn difficult to open!

I am going to take the roof light out, and ultimately reseal the unit, however, bearing in mind the horrendous sealing that is on it, it is going to take me ages to clean up the unit, and I may damage it in the process. I've looked on various caravan spares places, and the 400 x 400 push up cassette unit roof light only appears to be about £40. I am tempted to replace the unit while I am at it?

Opinions please?
 
Oct 1, 2007
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on the three i fitted on my self build
its retained by four longish screws
that go the bottom part of the vent
into the surface part of the vent
hardest part cleaning old sealant
and seperating old vent from the roof
( breaking the sealants bond)

use none setting sealant
if you want to change/need it again

take your time be safe while your
working on the roof
 
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DanielFord

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use none setting sealant
if you want to change/need it again
I have ordered some G4 mastic tape to seal the unit in. Opinions anyone?

The more I think about this, the sealant is up there already is going to be so difficult to cut/break, that I am going to damage to current roof light when I remove it, so I think I will get a new one anyway, it would be a disaster if I break the damn thing and don't have anything to fill the hole on the roof!
 

Minxy

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Aug 22, 2007
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Personally I'd be more worried about the damage that has been caused to the structure by all the water that's been getting in ... you really need to have a good shuftie once the roof light is out to see if there are any signs of rot in the timber and check the rest of your MH too for any signs of damp ...o_O
 
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DanielFord

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Personally I'd be more worried about the damage that has been caused to the structure by all the water that's been getting in ... you really need to have a good shuftie once the roof light is out to see if there are any signs of rot in the timber and check the rest of your MH too for any signs of damp ...o_O
Way ahead of you there :D
I should have mentioned earlier, the timbers around the aircon unit and the ones around the bathroom skylight are in excellent condition. Although a little damp to the touch yesterday. The van is kept under cover, so it only gets wet when we use it, this may have saved us more damage.
Also while I was up on the ladder this afternoon I checked in strategic locations for squidgy roof syndrome :D

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Minxy

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Aug 22, 2007
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I replaced a couple of roof vents on a previous MH and it wasn't difficult but it did take a fair bit of time just to clean the roof up! If your roof vent is old you could well find it cracks so getting a new one is a good idea and will also save you a LOT of time! Don't be tempted to get a smoked/tinted one though if you've currently got an opaque or clear one as you'll regret it - when I replaced the ones in mine it was to take out some smoked ones and replace them with clear and the difference was literally like night and day!

As for the G4 sealant you've ordered, it appears to be mainly for fish ponds etc so it may actually 'set' which isn't what you want, IMV you need the proper ribbon sealant which stays a little bit 'tacky' as this keeps the watertight seal as those that 'set' don't flex as much and can let water in.
 
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DanielFord

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As for the G4 sealant you've ordered, it appears to be mainly for fish ponds etc so it may actually 'set' which isn't what you want, IMV you need the proper ribbon sealant which stays a little bit 'tacky' as this keeps the watertight seal as those that 'set' don't flex as much and can let water in.
It said G4 caravan sealant, but will check that it does not set, if it does, it'll be a trip up to the caravan shop :D
I'm intending to use meths and a scraper, and quite a lot of elbow grease to clean the old rubbish off of the roof, so hopefully it shouldn't be too bad. Just need some decent weather now.

I am hoping I have ordered a like for like replacement roof light, but will not know until the thing actually arrives.
 

TheBig1

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g4 tape mastic is designed for the job

removal is very straight forward but don't force it or you can easily damage the roof. unscrew then run a scraper round the edge, then slowly lever it out using the scraper a few inches at a time. manually scape off what's left, then clean up with white spirit and rags. don't just put soaked dirty rags in the bin either.

refitting or replacing is easy too, just tighten the screws evenly, but not overtight so you don't squeeze out all the mastic

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Minxy

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Aug 22, 2007
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Be careful with the scraper, when you've got most of the sealant off get an old credit card and use that for the last bits so that you don't damage the roof.
 
Nov 2, 2014
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Hi g4 sealant goes off ive just sealed my pond again in places had little crack,but really good stuff regards
 
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DanielFord

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Thanks for all the answers, sounds like for once, the sealant I ordered was the correct thing. Just waiting for the new roof light to arrive, and then I'll get up there and replace it.
As for removing the old mastic, I've got a wallpaper scraper that has a sharp edge, I figure this will be the best tool to remove the old rubbish.
 
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DanielFord

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They say that a picture paints a thousand words, and so because I can't repair the damn thing yet, here is a picture. Also, I got asked in a thread why I do my own servicing and repairs, I would point out that this was done by a professional!!!
IMG_0464.JPG

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Minxy

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Aug 22, 2007
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Since 1996, had Elddis/Swift/Rapido/Rimor/Chausson MHs. Autocruise/Globecar PVCs/Compactline i-138
Thanks for all the answers, sounds like for once, the sealant I ordered was the correct thing. Just waiting for the new roof light to arrive, and then I'll get up there and replace it.
As for removing the old mastic, I've got a wallpaper scraper that has a sharp edge, I figure this will be the best tool to remove the old rubbish.
If the wallpaper scraper has sharp corners be careful they don't 'dig in' ... if you have an old one with rounded corners that would be safer. :)
 

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