Change the tensioner and belt, and test drive it upto temp. Hopefully doesn’t over pressure the cooling system. Likelihood is head warped if driven for long without coolant though.
Might also be one of these
https://www.ebay.co.uk/itm/394294827529?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=gnvCGhCvRzm&sssrc=2349624&ssuid=GrrGYAMmQ8i&var=&widget_ver=artemis&media=COPY
https://www.ebay.co.uk/itm/234743566487?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=gnvCGhCvRzm&sssrc=2349624&ssuid=GrrGYAMmQ8i&var=&widget_ver=artemis&media=COPY
I think you need one of these.
I hated the new defender when seeing the pictures leaked during its development through to its launch, but as time gone on it’s grown on me to the point that the Discovery 5 is going and I collect a new 110 towards the end of July.
You can if you loosen the bolts so you can turn with your fingers, then cut head of bolt with hacksaw then unwind rest of way out. The bolts are 25mm and it’s the bolt head that stops it coming out as it fouls on the housing. On reassembly swop bolts for 20mm ones then you never have problems again