I am also trying to resolve an engine overheating problem so have been following this thread with interest. My problem seems to occur intermittently. I've taken many of the steps suggested in the thread but don't know yet whether I have finally nailed the problem as the problem is intermittent. When I spoke to Beta about possible causes, one thing on their list of suggestions was whether the water filler cap needs changing. Is it the right pressure rating and/or is the spring weak after so many years in service? It seems too simple to be true but for just a few quid it can be changed and that possible cause eliminated. My engine used to run constantly at 80 degrees for 14 years, then it started edging up to 100 for no obvious reason, and now after some fettling it seems only to edge up to 90 degrees. Interestingly, I've also had gearbox problems recently but always considered the two problems were not in any way related. I've done a bit more fettling in the last day or two so will find out later this I week whether my overheating problem is cured permanently.