Rain water leaking from under dash

[Paulusvrotius1]

Hi guys, I'm hoping for a bit of advice from the e30 guru's here.
I have a water leak from behind/under the dash when it rains.
I have cleaned out the channel and drain from under the grilles in the scuttle which were blocked but I still have a leak. The water appears to drop straight onto the transmission tunnel so I'm guessing the leak is from the heater box area.
Before I tear the dash out are there any suggestions of where I can look for a possible cause?
Many thanks in advance.
Paul

[biffer]

in the engine-bay,on the bulkhead immed. above the back of the cylinder-head,remove the rectangular panel that covers the heater-box(4 screws + move wiring to one side)

you will see a shallow drain- channel running along bottom of heater-box-either this is clogged with debris, or the elephant-trunk(google) that it drains into is blocked.

tip some water into n/s grille below windscreen,this will end up in the gully,which if it is clear,should not overflow onto tranny-tunnel.

cleaning crap out of gully,or cleaning trunk out should sort it.

[Paulusvrotius1]

Thanks Biffer, I cleaned out the 'Trunk' which was totally blocked but didn't remove the black cover you describe. There was a lot of crap under the grill covers so I probably missed some. I will do this next week when I'm off work again.
Many thanks for the advice.

[magpie]

failing that underneath the battery tray rots out and the heater box that is bolted to the inner bulkhead scuttle panel has a foam gasket , when these fall apart the inner bulk head rots out around the heater box .

[Paulusvrotius1]

Thanks Magpie, I will have a good look at these areas as well.