Hi to alls
On a Jaguar MK2, the water entering through the scuttle vent (the air intake located at the base of the windshield) is normally managed by a drainage system designed for this purpos
The scuttle vent with it'sventilation grille allows fresh air to enter the vehicle’s ventilation or heating system. It is also exposed to rain, so a drainage system is essential.
Beneath this grille is a collection tray, also known as a plenum, which collects rainwater. This tray is designed to separate water from the intake air.
How does the water flow out of the plenum ?
Are there any risks of water infiltration into the cabin ?
My best regards
Gérard

 

There is a drain at the bottom of the scuttle vent chamber that allows water to exit into the engine bay where there should be a long rubber hose the water flows down to the side of the gearbox. If your scuttle has been open to the elements this could be blocked with leaves and detritus but it is easily cleaned out with a coat hanger wire.
The photo below shows the drain hole coming out into the engine bay on my S Type which should be the same as the Mk2.

 

try googling "jaguar mk2 vent plenum drain hole" to get Google's AI thoughts on it, or something similar.

here's an old thread that posed the same question...

https://forums.jag-lovers.com/t/salo...ainage/29964/3

 

It is the same on the MK2. A rubber hose then drops down the firewall into the tunnel area. You need to make sure the plenum chamber is clean and rust free as if it blocks and rusts the water will drop into the cabin. You can remove the scuttle flap for access.