Radiator blockage

I HAVE had to have the radiator in my 1992 EB Falcon unblocked four times in the 230,000km it has done. It has required rodding out twice in the past 12 months or 12,000km, with expensive repairs to the cylinder head due to overheating. I am told this is a major fault with Ford six-cylinder engines and that Ford does not acknowledge the problem. My mechanic suggests rodding the radiator out every six months to avoid further problems. Will this loose sand ever be exhausted, will it affect the lubrication system and can you suggest any other solution, apart from switching makes?