Found this under the car tonight. Any ideas? Want to figure it out before I drive it and regret it.

 

Looks like the plug for draining coolant from bottom of radiator.
Check your coolant level.
Any visible leaks?

 

The coolant drain plug is black plastic with an X head, not a single slot:



Unfortunately I have no idea what size that coin is so I can't visualise the size of the plug.

Any signs of fluid underneath the vehicle? If not, consider the possibility of a neighbour with a (twisted) sense of humour winding you up.

Graham

 

As I recall the US penny is slightly larger than the pence.

 

looking at the parts manual there is a bunch of small plugs on trans but don't show details of head, is it metal or plastic? also one cent about size of a sixpence

 

Now you're talking my language.

Graham

 

Similar to a Plug used in a waterproof electrical box. Maybe have been related to a totally different job, not your car.

 

What kstevusa said!

 

Oyster. No leaks, no over heating. Coincidentally, I did get a low radiator fluid warning! The radiator fill box (can't remembers what it is called) was only a quarter inch low. So, I topped it off. Level measured with engine cold as per the manual.

Weird. That plug must come from my car.

 

home electrical box! I bet that is it. But, it does seems a bit small.

 

I agree with plug on a junction box.

 

Looks just like the level and drain plugs for the lower unit of my old 1960's Mercruiser. I don't think its a Jaguar part.