I investigated the slight weep from the thermostat housing yesterday. I can't see any damage.
In principle, removing the coolant rail and thermostat ought to be straightforward. There's only three screws holding it to the block: one on the thermostat housing, and two at the other end of the block holding the coolant rail. But the coolant rail is also used as a bracket to hold the engine wiring loom, and of course, with all the coolant hoses connected, things are pretty tight.
I had a go trying to separate the coolant rail from the thermostat, but with the inlet manifold in the way, this was proving challenging. Moreover, I was concerned getting everything back together was going to be even more of a challenge...! Also, when I was tugging on the coolant rail, coolant could be seen weeping from between the two halves of the thermostat housing.
Hmm.
I may need to bite the bullet and replace one or both the thermostat housing and the coolant rail - but to do this and maintain sanity will require me to remove the inlet manifold and make some space in which to work. I didn't have enough time to do this over this last weekend, so thought I'd put everything back together and tighten the three screws holding the two halves of thermostat housing.
Everything looks a little dryer now - but I suspect only a temporary fix before I need to take everything apart when I have time. In the meantime, I'll keep an eye on things.
Also, it was one of those days where I spent more time looking for dropped 10mm sockets between the block and IRD (my cheap Lidl endoscope proved its worth!) than actually doing anything more useful - and in my experience, when little things like that start to frustrate you, best walk away! LOL
Thermostat replacement - to be continued....