There is a small, ally nut 'elastic stop ring nut' which holds the timing belt roller in place. Someone has had a go at it previously and chewed the edges but it appears stuck fast. Usual tricks like heat etc have failed to release it. Has anyone come across this problem before - and found a solution? Ideally i want to replace it with an unmolested part
Not had that issue myself. Try the usual...heat, mole grips...penetrating oil etc I once managed to remove a mangled nut by filing it down on one side so that the threads were just exposed. I was then able to remove it with pliers as the torque had been released due to the nut being “split”. There’s probably not enough access to do that though.
That's the problem, it is really tight space wise I have the replacement which is light alloy, I wondered if that is why heat hasn't worked? Or could there be an electrolytic reaction with the shaft?
Get a good a grip on it as possible and then also turn the tensioner the same way. Providing the tensioner stud is secure in the head, it usually comes free. If the stud comes to, unscrew the lot and separate on the bench
If you can't cut the nut, you could try drilling it to get it to release its grip on the stud. Start with a tiny bit and then use larger ones until it lets go. This has worked for me in the past.
