Roof leak - Mercedes Sprinter ex-ambulance conversion

0kee

Hi All,
I'm looking for some advice on fixing a roof leak. It's an ex ambulance so I had originally thought the leak was originating from where the front roof lights and sign had been botched by the previous owner however fixing that hasn't stopped it. The main leak it coming down in front of the passenger seat. Dripping from the headliner. As there are a couple of other minor leaks (middle and back) I have decided to completely recover the roof. I'm looking at one of 2 options.
Option 1) Cheaper and easier (I think): Remove all the silicone (from previous owner) from joins and protrusions on roof (fan and aerials) and apply Tec7. Then cover the entire roof with a few lengths of vinyl wrap (orajet-3620-digital-print-vinyl from 365Plastics).
Option 2) Use the Professional Fibreglass / GRP Kit - 10 Square Metres kit from Fiberglass direct and recover the whole roof. This is more expensive and I'm a bit concerned I'll mess it up.
Any thoughts would be much appreciated. If you have another suggestion I'm totally open to hearing it.
Thanks

crabbypaddy

You don't say if its a panel van or a box body ambulance. Powder painted aluminium can be hard to bond to.

Before you take drastic measures its always best to remove bad sealant and start anew.

Silicone is definitely the wrong thing and tec7 can have poor adhesion to painted surfaces.

Remove all the old sealant, properly clean, scuff and de-grease as necessary apply a proper sealant like the wurth stuff recommended on here.

Vinyl would be a rubbish job you'll end up with pockets over contours and sealant lumps that could puncture and retain water.

If its a small amount you must also consider the possibility that its just condensation just breathing produces up to half a liter a day per person, cooking / boiling the kettle / gas oven could be another couple of liters. Water will condense on the coldest part of the van so if your roof isn't insulated thats a lightly place. Ventilation is essential, if you've sealed up the roof vent / fan you have to have the roof lights open when you're using it and you need to air it out or use a dehumidifier.

If the ceiling isn't insulated I would rather invest the time, money and effort in stripping the ceiling which will allow you to find the source of the leak and insulated it before reassembling.

0kee

Thanks for your answer Crabbypaddy. Sorry yes, should have said it's a box body type ambulance would have looked something this in its day (Google "ambulance_scaled.jpg" first picture - no pictures or url because I'm still a new user??) so I'm assuming it fiberglass.
It's not condensation, sure of that. Yeah, was thinking the vinyl might be dodgy. Cant get at the ceiling but it is insulated.

Aidan_M_M

Tec7 is rubbish. I only use Wurth sealer.

crabbypaddy

Its hard to know where the water is coming in in the ambulances because it accumulates above the fibreglass ceiling and runs along it. When I had a leak it would pour down through the light fitting when you were going up hill. First thing I wouuld do is remove all the vents / roof lights, remove old sealant and reseal them. You'll probably find the air vent is very corroded might need replacing.