It has gradually got worse to the point where it has started needing water adding every 200 or so kms. When the filler cap is removed it blows off quite a bit, indicating that the system is getting pressurised from within.
After a bit of a rummage on the interweb, it looks like there are 2 likely causes....
1. The gasket has failed - quite possible because it was not skimmed when I replaced it last time.
2. The head is cracked. This seems to be a fairly common issue with the Td5, so with this in mind, will my cylinder block test kit work on a diesel engine or is the liquid change only effective for petrol engines?
One wag posted this in a forum...
A new replacement head with valves and springs is just over 1000 Quid and it still needs to be shipped to Cape Town, so I need to be certain it's the problem before shelling out for that, plus new bolts, plus this seal and that seal, plus duties and all the other nausea.The normal reason for over pressursing / loss of coolant is a failed head gasket, but seeing as you've got a TD5 I'd bet my last square of toilet paper on it being a cracked cylinder head, sorry to be the bearer of bad news (if I'm right of course) but it's just the way they are. I think tyres last longer than TD5 heads! (I drive one too)
Any ideas, anybody?