Allis Chalmers 940 loader coolant leak

I have a 1976 AC 940 loader. Today it started leaking coolant around the base of the injector closest to the cab. I read in the owners manual that there is a sleeve nozzle holder that goes thorough the coolant passages to help keep the nozzles cool. I believe this is where my leak is coming from. Has anyone had this problem and do I have to remove the head to fix? thanks