Attached is a picture showing the engine number location and adjacent to it is what looks like a drain plug. This is on an '03 XK8. Can anyone confirm it's purpose?

 

I've only ever done this on my Porsche BUT,,, if it is infact - and you have positively identified it as a coolant drain plug - on coolant change you can drain near ALL of the coolant out of the block as well as the more typical rad and hose system when flinching the sysyem. It is generally not possible to drain the coolant completely because even if you flushed with a ton of water,,, some amount of water would remain in the block.

IF this is a coolant drain for the block I guess I would be asking myself is it necessary...? Or, could I get by with just a regular flush. Could open a can O worms in a tough spot to access (unless you have the engine is out?)... But that's just me.

There should be one on each bank IF that is a block drain. I'm not sure that there is one on these motors.

Anyone?

 

Possibly the location for fitting the optional block heater .........

Graham

 

That^^^
I think Graham is rightright
I wouldn't mess around with it.