Tailgate rotting from the inside out

[OddJobBob]

As the title says, my tailgate is rotting from the inside. When I opened the tailgate the other day, water poured out of the elongated holes at the bottom. I hadn't noticed this before but the small patches of rust had spread. There doesn't appear to be any drain holes at the bottom like doors have and I can't see how the water has got in. I can't access the inner surfaces of the tailgate do how should I tackle this? Pour in rust remedy and then pour in waxoil? Any suggestions appreciated.
Cheers
Rob

[kevtherev]

It gets in through the seal usually.
have you looked at the top of the gate? ...any holes?

[Wookster]

As previously the cause is probably a leaky seal but the damage has been done.
If you can weld it's cheap enough to repair, otherwise a new tailgate with good seals might be a better option.

[OddJobBob]

Thanks guys. The seal looks ok - no sign of damage or holes. The rest of the tailgate looks sound so I can't see how water is getting in. The window seal also looks ok. I can't weld and the outer skin is ok so I don't want to replace the whole tailgate. I'll have to climb in the back and get the wife to hose it down. Might just fire in some Dinitrol Corromax.
Cheers
Rob

[Wookster]

If you can trace the leak then it's probably worth a cosmetic repair with some filler & fibreglass.
Filler is porous but you could paint the fibreglass resin onto the interior of the tailgate to seal and strengthen the area.
Not saying it will be easy cos of access, but I think it's worth doing as the external skin is good.