Cure for rain leak in 306 - Rob-406Turbo
I had a Pug 306 which leaked rain water and would have soggy carpets front and rear off side (occasionally dripping through the interior light fitting!.

Having read numerous forums about this issue being a seal round the windscreen, ariel hole or blocked gutter under the bonnet I decided to investigate. It was none of the above.

The problem was caused by the drain pipe from the rear offside whihc runs down the rear quarter panel in to the wheel arch - thisis fine on the near side but on the offside there is the fuel filler etc. This means the inside of the rear arch has a lining - as the pipe poked through the inside arch it bent back on its-self against this lining causing a blockage (nice factory fitted sunroof!). So having straightened this out it was OK.

The easy test for this is to wind the sunroof back and block the front drain holes with tissue (test they aren't blocked!), fill the sunroof surround with water and ensuring the car is slightly up-hill so the water has to use the rear drains - you should see the water disapear from both sides (appearing under the car infront of the rear wheels).

I also found that there are plastic plugs at the end of the sunroof surround\gutter where the rear drains are attached - mine weren't the best fit, 1 blob of bathroom silicone later they were!

This was a 3 door, but I'm sure the rest are the same - a friend had the problme on a saloon 306.

Hope this helps.
Cure for rain leak in 306 - turboman
I had a similar problem but the rain come in under the passenger side.
Front. To solve the problem I cut a peace of old hose to length and.
Put it around the old rubber seal. I do not now if it will cure yours.
However, it is worth thinking about.

Cure for rain leak in 306 - Rob-406Turbo
I forgot to mention - check the plastic behind the dooor panels. Especially around the speackers!
 

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