Water squirting out of a white plug?

[jesse'sVT5.0]

Hi all,

I have a VT SS 5.0 as my handle suggests

My wife has been driving it the last fortnight. We swapped cars this morning and on my drive to work the temp gauge was going crazy (basically moving in relation to how much air was flowing). I pulled up to park and there was a hissing and water squirting out from the left hand side of the engine block. I can see a white plug in the underside if the block that the water was shooting out from.

Anyone have any ideas what the plug is and will it be an expensive fix? There is, by luck, a mechanic at the end of the street I park the car at work so I have to cross my fingers and see if they can help.

Thanks,

Jesse.

[VYMAD]

Not temp sender, eh?