My son's 2004 Mk6 1.25 Fiesta has leaking core plugs. We know this because our local garage drained the spark plug well on Friday to replace the spark plugs, HT leads and coil pack to cure an intermittent misfire and engine management light. Although they had previously pressure tested the cooling system and found no fault, the coolant level suddenly dropped yesterday afternoon after only a few miles.

We removed a spark plug lead this afternoon and siphoned out about the same amount of pink water as had been lost from the reservoir so it is fairly conclusive!

Wikipedia http://en.wikipedia.org/wiki/Core_plug mentions using expandable rubber plugs as replacements and I wonder if anyone here knows whether this is possible on the Duratec cyliner head as they do seem prone to failure from the number of threads on the subject.

If not, what sort of cost is usually involved in replacing these? It looks fairly straightforward on paper but then reality is often different.

Hmmm - £36 including VAT to replace them both. Don't know what we were worrying about!