water leak - but where from... ?

[X5-D-Sport]

Hi People,

Got a water leak from my E53 3.0D facelift - 2004.

it's intermittent.. as in that some days it wont leak for days - then does.

The vehicle sat idle for 2 weeks... no leak or puddle underneath either...

checked level daily - all good.
Started the beast yeaterday, looked all round with the torch, not running more than 2 mins to develop much water pressure.... but lots about 1/2 pint with a damp puddle underneath this morning - defo anti freeze sweet tasting  - YUKKK..

Any ways, looked around the header tank - dry & clean...
Pipes all dry & clean looking.
Appeared to be coming from the LEFT/passenger side of the engine - re the puddle location & drips.

I've been looking for the tell-tale chalk deposits on parts & also damp bits n drips...

I am doing an exhaust manifold & gaskets change some time soon & bought a new Water/Flange pipe dubree part that lives under the inlet manifold incase that's cracked, or the gasket has failed, but all looks OK meanwhile.

I'm happy that it's not a Head-Gasket leak, as that would specifically leak & use water when the engine is running... but it doesn't 

Are there any frequent or more likely failure parts to hunt out for leaks around the engine bay ?

[X5Sport]

Anything from the plumbing connected to the Webasto unit?  It will only run on cold days and the valves will be closed it it isn't in use. Might explain the intermittence?

[X5-D-Sport]

Excellent idea... that's one thing I've not checked..
Thank you.