Sunbed shaun

I was sitting in a car park then I could smell coolant so i popped the bonnet and noticed a bit steam weaping from the leads so I pulled the leads out to find coolant covering the plugs. I checked the oil, oil is nice and clean, coolant is nice and clean, no oil mixed in where the plugs are and heating is staying half way. Any ideas?

Sunbed shaun

I've been looking about on the net for a while and sounds like the problem is the core plugs. Can anyone let me know how these are removed, they have an allen key hole on the top but peoples saying they aren't screwed. How do i add the new ones which I can't pick up til this afternoon. Also what sealant do I use?