Just happened to note a post on another forum about the degradation of the Yanmar diesel fuel return line to diesel tank.
The hose on this guys engine had hardened and cracked due to heat/age. The result was diesel fuel all over the engine…yikes!
I am alarmed because I ran into just such an issue with the coolant overflow tank line from the heat exchanger. When I did the mounts I noted this line had badly deteriorated and I replaced it with a clear silicone line so I could see what was going on with coolant flow. I did not look at the diesel return pipe at that time but I am headed down to check it today.
Given the age of some of our engines this seems like a very good thing to check.