Coolant leak

[JMO]

Hi all.

I have been looking under the bonnet and have realised there is a small coolant leak coming from the steel pipe that goes to the lower thermostat housing. It only seems to leak when the engine is cold. Could this possibly be an o'ring problem.

If it is, what type of o'ring am i after, ie. is there a specific o'ring made for this application or is it just an o'ring that fits.

Any help would be appreciated.