Hi all our jtd150 is showing signs of cylinder head gasket trouble it has never needed its coolant topping up! But it has now started to overflow at the expansion tank not much but a commute to work is enough to put a bead of pink coolant around the seam around the tank. I have ordered a new cap for the expansion tank, a new thermostat and I will change the coolant (it has been in over four years) if that does not work I will try K-seal though I am not keen on additives’ a look on Ebay at z19dth cylinder heads reveals that they do corrode so it will need skimming, a new gasket and bolt set. Still can't complain it has been trouble free for ages.

Sorry to hear from your problem. Do you want to replace the hose or the original thermostat. I understand from postings written by you that the temperature was allways very stable and spot on.
Does the liquid contain oil residue, remnants?

Hi and thank you as you know I fitted a hose type thermostat I am certain that it has not caused the head problem the temparature is still very stable the coolant should have been good for another year, also I cannot see why the cap should fail but I want rule out the easy stuff before I spend a couple of weekends in the garage. Our car is ten years old and has 115000 miles on the clock so it is probably down to that, though with hindsight I would have changed the coolant every two years. The second hand cylinder heads on ebay all show corrosion to the head face those water ways are
very close to cylinder bore , I did really get my foot down! Overtaking a lorry north of ashbourne some weeks back. Just checked and gasket and bolt set £55 and the skim is £40 at swad diesel's so I will try K-seal to get us through to next spring.

Telegraph did you see the article "Croma coolant tank over flow" by El Kabong in the Croma section? Posted 29-11-2013. https://www.fiatforum.com/croma-ii/338875-croma-coolant-tank-overflow.html

Just had a look and I can see how some overflow might be normal but I am concerned as my tank is wet after a three mile drive to work, I have read that the egr cooler can boil the coolant and lead to over flow. I have not touched the filler cap since the thermostat job until two weeks ago when I noticed it a little low and wet. I will monitor it over the next week or so, I will see if there are bubbles in the tank by over filling it and see what I can see.

I'm wondering if you are having a pressure build up problem as a result of inserting the in-line tube thermostat.

Did/does the in-line stat have a built in bypass? If not, or it is too small then there may be too much restriction in the system and the pump is building up pressure due to lack of circulation?

Hi, I did wonder if that may be the issue so I have just received a new octopus thermostat but thinking about it I have had no issue with overflow until that overtaking I mentioned. Looking at the new stat the valve is at the exit and the hose stat function is just the same the valve itself looks to have the same open volume. I have fitted a new filler cap as a first step.

To my surprize a new cap for the expansion tank has fixed the overflow it is completely dry after a drive with loads of boost to prompt it! The only thing I can see wrong with the old cap is the sealing 'O' ring is slightly deformed. A great relief I really did not want to take the cylinder head off.