Hi All...and Happy Easter !

I've been living with a leaking sunroof all winter while fixing other more serious problems like fuel leaks. Now that the weather is improving I'm going to have another attempt to resolve it.
Last time I tried to fix it I removed the roof lining and got access to the front drain pipes and found they were in perfect condition and yet water runs down the outside of the pipes and runs out of the A pillers onto the floor.
There seems to be a spongy gasket in the join between the sunroof and the car's roof and this is soaking wet so I ran sealant around this joint on the outside with no effect.
My next theory is the rear drains are blocked and the water is running to the front but I can't see an easy way to get access to these without removing the sunroof and I cant find where they drain to ?
I've searched the archives and cant find anything similar, anyone got any other suggestions.

Thanks,
Gary

'73 450SLC (Euro so lots of hp)