second the combustion gas test kit. Just make sure to remove the CDR and block off the point where it enters the engine. before running the test, then block rad with a chunk of cardboard and run up to operating temp to where you can see coolant circulating before testing. Blowby gasses entering through manifold can give false bad HG reading if faulty intake manifold gasket. so test first with blocked cdr, if reads clean good HG, if fail bad HG or cavitation, , if clean test again with cdr attached, if it fails then bad intake gasket , hint, leave on longer than instructions say, those are for gas engine, diesel is hard to sense. Get the dual chamber tester if possible, hard to contaminate, i for either use a baster etc to remove an inch or so of coolant from rad so not to contaminate test fluid , it will change colour if contaminated with coolant
