I decided to clean up a spare water rail before tackling this task:
I replaced the cable ties as you can see.
Even on this replacement rail, there was rust on the inside of the pipe where the O-ring sits. I cleaned this, finished with fine grit paper and gave it a light coat of smoothrite paint...
No idea whether this is a good idea or not - guess I’ll find out!
Getting the old rail out was quite a phaff. Much easier if the inlet manifold were removed, but still doable. I cut the cable ties holding the engine wiring harness first (there are for to remove) then I unclipped the coolant hoses (after first draining the coolant reservoir).
This frees up the coolant rail, and then it was a case of removing the two retaining screws (both 10mm head screws). Pulling the coolant rail from the thermostat housing was the most challenging part - partly because of a slight lack of space, but mostly because it doesn’t want to come off! Needed a fair amount of patience and wriggling while pulling; it eventually came free.
This is what the inside of the pipe looked like:
It looks worse than it is I think. The old O-ring had expanded and felt spongy in comparison to the new one that I replaced it with:
It’s all back together now. It was quite straightforward but I had to clean the thread on one of the M8 screws with a die, but once I got the mounting holes lined up, it all came together smoothly.
Fingers crossed this is the coolant leak fixed!