@Gordmac check when the timing belt was last changed. Should be every 5 years or 500 hours. It’s real simple to change (even I managed it) and you can get a Bosch full kit for around £100. On these you don’t need the Yanmar stuff because they are (well mine is) Toyota Land Cruiser engines. If you can establish from a Yanmar mechanic exactly which Toyota engine it is then your on to a winner with spare parts costs. Access aside, they are relatively easy to work on. So far last season I......
striped and descaled the complete cooling system.
removed turbo, then re fitted once reconditioned.
changed anodes,
changed oil, filters etc
changed coolant
fitted an oil catch can.