tusabes

Yes that’s the cause for the water in the rear seat

wallyp

The water from the HVAC plenum does not travel into the boot.

It is not uncommon to find flooding in the boot. This can get in thru leaks around the taillight housing, thru or over the lid gasket, around the rear window seal and thru loose or missing rubber plugs in the sides of the recesses on each side. Leaks into the left rear fender well will destroy the electronic and electrical devices installed there.

Harris Ali

Thanks wallyp. I did think it was so odd for the water to travel all the way back to the rear. I think what I will do is hire a ramp and take a good look at all the points which are suspected. The front and the rear as well that you mentioned. It will be cumbersome and will have to take apart the fittings, carpets etc.etc. and by asking questions here on this froum i was trying to avoid this by getting a direct ans, but seems there isnt a clear ans for this. I'll be sure to share what i learned though.

Regarding rear seals, i really cant see how can such a large amount of water creep in from the lights fittings etc. Very odd!!

tusabes

You are talking two different water areas - water in the boot (trunk) cones from a trunk leak- could be taillight gaskets or other trunk areas

water under the rear seat comes from the reed valve In the engine compartment clogging , and water that travels front to back seat under the carpeting in the electrical trough in the floor pan

Ali9595

I thought i should put this here, in case it helps anyone else.

The water ingress was from two small screws in the side of the boot (not the lid itself). These were just failed screws.... All sorted now! Thanks everyone for the help.

Haris

S430AMG

Cleaning out that drain every few weeks is the first thing I learned about this car (on these forums) and do my best to do on regular basis.