leaking vaillant 242?

Please ignore the below, I read your boiler as a VCW242 which it may not be

Carefree
December 2010

Whilst not wishing to argue, I'll wager the leak is above where you are specifying.

Look at the top of the boiler (right of the flue) at the back, there you will see a brass auto air vent on a silver tube, see if that is where the leak is. If so, you can screw down the black cap on top as a temporary measure, this will see you over the next couple of days. You can then arrange for its replacement.

Please let me know if this is correct?

Carefree
December 2010