I'm sure it's not raining in the garage

[Nick Lettington]

... So where did the water come from that put the rust stain around the plug?

   

[Alan]

You’ve been out in the rain, or washed the car and it’s dripped through the bonnet hinge.
The water manifold is leaking.
You have a leaking head gasket.
I suppose the head could be cracked, but I doubt that.

[Mike Costigan]

You don't say what model, but if it's s a standard car then it's likely a drip from the bonnet hinge centre mounting.

[Nick Lettington]

Senility is creeping in. Saturday 14th... All day in Culver Square, Colchester. Should really have engaged the grey matter first.

---

I have never knowingly washed my car!

[Howard Wright]

Hi Nick

How long ago was the head replaced?  Water can find its way up the threads on the middle head studs.  It will pond slightly around the plug but evaporate on the head.  After a short time the threads “heal”.

I’d keep an eye on it but not worry too much.

Cheers

Howard

[Nick Lettington]

Funnily enough, I had all kinds of trouble trying to get the head off a while ago... Largely because of rust around the studs. Ruairidh suggested seepage may have been an issue. I'll just add it to the list of things to ignore.