PetiteFleur
Well-known member
From the fact that the system runs properly when you prime it, it is clear that the water loss over time is problem. Do you have the black volvo strainer? The seal on this strainer is created by an inner plate that seals on a rubber gasket on top of the white sieve. When you unscrew the top you should have to pull quite hard on the inner plate to break the airlock. If you do this without closing the seacock you will have to re-prime the system in the manner you describe as you will when you dismantle the pump. If the inner plate is not sealing or is missing then the water level will drop. Although the system will self prime in theory, as you have found it can take a long time during which time damage can occur.
I had this problem with my 'new' strainer when I re-engined - the strainer cap had to be really tightly screwed on - I well greased the threads and made a 'tightening tool' from scrap plywood as I couldn't tighten it enough by hand. Not sure who the strainer manufacturer is but believed to be Italian.