There is a battery breather tube fitted on my X type but why ?
On all the vehicles I have ever owned, over several decades, none have had this addition. I have never detected any problems so far.

I can understand the need if the battery is fitted in the trunk ( boot )and any fumes are best dumped outside but it seems superfluous when the battery is the engine dept up front.

Is it a carry over / standardisation from another model that had a battery in the trunk?

 

henry, it is there for the same reason that you need it for in the trunk. The battery is inside of an enclosed space. It can't really breathe. So, to allow the fumes to vent properly, they fitted the box with a vent tube to prevent hydrogen build up when you are taxing the battery heavily.

 

Chris,
If it's in the engine compartment isn't there a mighty draught through the radiator?

 

Steve, yes, there is a might draft through the radiator, but do you have a draft into the passenger compartment? I don't think so. Same thing with the battery. You have enclosed the battery inside its own little "passenger compartment". If you look in the rear of our car, there are vents back on the rear shelf to provide ventilation to the passenger compartment. It doesn't take a lot of ventilation, but you need some to prevent the build up of undesirable gases.

 

Chris
100% on XK's with battery in boot - I've never looked under an X-type bonnet, just the OP said the battery was in the engine compartment.
If it's in a separate box then a vent's needed, no question.

 

Another point, the fumes that are vented from the battery are very corrosive.
You want them out and away from the car as fast as possible. Even when
the car is just sitting there will be a flow through the vent as the ambient
temperature changes.

Pete.