These are the potential water ingress points that I’m aware of on the mk7 / mk7.5 Golf that have been mentioned on various Golf forums over the years. It would probably be worth working through the items on the list, eliminating those that aren’t relevant to your water ingress issue, and investigating in more detail any items you have left on the list. Good luck!
- blocked cabin pollen filter.
- a/c drain tube becoming detached from the evaporator, draining into the car interior rather than onto the ground under the car.
- damaged / distorted or poor fitting door or window seals.
- replacement windscreen not bonded correctly to the car bodyshell.
- blocked drainage hole in windscreen scuttle panel.
- cars with a sunroof - blocked drain pipes.
- damaged / broken rear door speaker seals, resulting in water draining into the rear footwells. This is quite a common issue.
- damaged / perished grommet on the bottom of the drain pipe from the hatch release handle, allowing water to collect inside the tailgate and drain into the boot underfloor area and spare wheel well. Again quite a common source of water ingress.
- damaged / cracked rubber sleeving covering the wiring from the car into the tailgate above the tailgate opening (between the tailgate hinges).
- poor seal between the tailgate hinges and where they’re attached to the bodyshell above the tailgate opening.
- damaged seal between the roof and roof mounted aerial (tell tale signs would be water staining on the roof lining and possibly a damp rear seat).
- damaged or perished seals between the rear light clusters and the body panels the lights are fitted to.
- failed seals around the air pressure equalisation vents in the lower rear quarter panels either side of the boot (these vents are ‘hidden’ behind the rear bumper cover). A tell tale sign of failure of these vents is water in the spare wheel well and / or in the small storage compartments either side of the boot floor.