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Topic: Educate me on the Sunroof tray and rot / rot prevention (Read 531 times) previous topic - next topic

Educate me on the Sunroof tray and rot / rot prevention

Hello all,

I've had to park the mk2 out side whilst some works are happening to my garage and have found it leaks. Door membranes are freshly applied and found my sunroof panel was wet and water had made its way towards the windscreen - car was parked nose downward.

I checked the drains and they were clear so went digging and removed the headliner and found a rust hole where the panel locates when the roof is open. I doubt this was the source of my leak due to the way the car was parked however it is a problem to solve anyway.

Generally otherwise the sunroof tray looks tidy however realise it's likely to rust inside out so am wondering what sort of preventative measures could be taken to save it? Spray a light layer of wax into the channels is all i can think off?

With regards to the hole I have I can cut it out and weld (or even cut out and use a marine grade bond as will benefit a water tight seal and less chance of unpainted metal coming into contact with water/air). My Q here is from looking at this part of the tray I can't work out how water would normally escape this section as the drain area doesn't apear to be connected at the rear so assume water is supposed to travel forward when car is in use? With the hole I could use my lance and spray a light layer of wax in there - good or bad idea?

Some pictures. I had half expected the tray to look the same as what is in my Corrado and not to see something welded into the car so am keen to prevent / protect the draining channels. The visible part of the drains up from are in good condition.





Re: Educate me on the Sunroof tray and rot / rot prevention

Reply #1 –
Just to clarify what I meant by the sunroof tray part not being connected to the rear drain - the metal is folded upwards where I have drawn the red line so I think water couldn't be able to escape to that drain.

Is water even supposed to get to the part that has rotted - would it point towards a sunroof seal being leaky (I know it is suppose to leak some water but perhaps not past the drip tray

Re: Educate me on the Sunroof tray and rot / rot prevention

Reply #2 –
The problem occurs because the sunroof seals do not seal.  The drains don't drain effectively so water collects in there, it splashes about and evaporates and condenses.  The steel tray is not painted so rust soon starts to form.
I discovered this problem when my car was just two years old.  I worked with abrasives on extensions, a tube on a vac and brushes on extensions.  I rubbed the rust to bare metal, cleaned up, rust converted, primed and top coated.  I didn't use wax in the tray because I didn't want to block the drain tubes.
If the car is a keeper I suspect yours needs to come off and be welded.

Re: Educate me on the Sunroof tray and rot / rot prevention

Reply #3 –
I would expect by design that that part is not supposed to have water run into it as your pic clearly shows there's no gravitational way for any water in there to get into the drain tube. It's possible.... and I mean VERY possible as in most likely, that one or both of the rear drain tubes is blocked so water is backing up and overspilling into this area.

Now I haven't given it much thought before now, but I do remember a time, and have had others report the same issue, when all seems well until you apply the brakes for the first time on a drive and this action pours a load of cold water down the back of your neck.

Seeing this now makes it clear that water collects here and would shoot forward in this situation. You may not have experienced this since you appear to have an extra drain hole.

The good news, is as this is an inner skin I would have thought it could be cut out and repaired, either with a simple patch welded in or if you need to go larger a donor body cut, and as I said with this being an inner skin as long as it's done carefully, and the heat is managed it should effect the out roof skin. Be careful of any wax in there though as that has a tendency to catch light and that could well flash the roof paint. I'd use a airline with a thin nozzle through that small hole you see there.

Re: Educate me on the Sunroof tray and rot / rot prevention

Reply #4 –
Cheers guys. As luck would have it I am booked in with Dan Tinkler/DST Rustworx next year and was debating whether to send this car or another up to him but it looks like my decision is made. I have put my mk2 on pause as need the scuttle and ideally some rear arches as someone rolled them and no doubt will find other odds and sods - I am sure Dan can get the sunroof tray out and sort it rather than me patching it up from within. I do hope keep this car (and the Corrado) and get rid of anything else I have so will aim to do it right. It is defintely beyond me getting the sunroof out and welding it in without warping the roof etc.

Makes sense re the rear drains being blocked and for it to back up and fill the tray, perhaps from rust on the bits I can't see! 

Re: Educate me on the Sunroof tray and rot / rot prevention

Reply #5 –
I've never had my headlining off so have nothing to compare. I'm assuming the rusty hole above the red drawn line shouldn't be there?
I guess it is a case of doing the best repair without creating more work / bodging.
Could all the rust be removed and a piece of metal bonded in? Less scope for distortion widespread damage. It won't be original but could provide an alternative repair.
After all many new cars use bonded panels.
1991 Tornado Red BB 8v GTI Moredoor
2008 Skoda Octy Scout aka dirty diesel

Re: Educate me on the Sunroof tray and rot / rot prevention

Reply #6 –
Quote from: AndyBa on
I've never had my headlining off so have nothing to compare. I'm assuming the rusty hole above the red drawn line shouldn't be there?
I guess it is a case of doing the best repair without creating more work / bodging.
Could all the rust be removed and a piece of metal bonded in? Less scope for distortion widespread damage. It won't be original but could provide an alternative repair.
After all many new cars use bonded panels.


Cheers Andy, I'm debating either that option with bonding instead of welding in that area or go mad and drop the whole panel - cut out/clear up and bond in and also do what pwardy suggested and get extensions & wire to rub down the inner drain channels and paint (as protection, they are fine from outside but would benefit with clean up and protection).

I'm leaning towards the easier of option of repairing in situ. It's not structural and is on a flat part of the metal. The drains are good/solid so if they can be protected and preserved from within then why add the extra cost and risk of paint damage to the roof is my current thinking.

The car will be dry stored in my ownership anyway but I don't want to worry about using it in rain etc.