So I'm sorting out the heater on my '71 series 1. It looks like the vacuum tubes and the switches have both perished.

I noticed the air intake under the grill behind the bonnet/hood has a hole between the engine compartment and the air intake. It's about 2" in diameter. I'm assuming this is to allow water to drain down into the engine compartment and onto the road, but why so big? Is there supposed to be some sort of plug with a drain hose in there? This hole seems like a great way to let engine fumes and smells to enter the cockpit when the air intake flap is open.

 

normally there is a 90 degree elbow hose connected at the firewall end of that hole.

it is a water drain for the cowl vent. The hose has a closed end rubber "membrane" so that the weight of the water opens it and allows it to drain and then it closes again.

if you cannot find the original part, just get a 90 degree elbow hose that fits over the pipe. If you look for Ford Vans in a salvage yard, they have a similar membrane piece that can be attached to the end of the hose with glue.

 

Thank you. Yes I found it in my parts manual: BD34735 Plenum drain tube. With BD34737 on the bottom. Most of the classic cars I have worked on have a small (3/8-1/2") drain at the bottom of the air intake. I'm not sure why Jaguar felt the need for a 2" drain. Since the drain tube is unavailable I'll try a DIY fix.