Yanmar 315 Engine Alarm - Low level coolant

[lawrento]

Hello Albineers,
Just back from a long range trip running up almost 300 Nm .
Lucky for me, the Low Level Coolant engine alarm sounded while I was 4Nm away from my marina.
Added coolant to engine and expansion tank.... conmplete the journey at low rev.
Next day while engine is cold, check again coolant level.... no significant Loss of coolant in engine and expansion tank. Check other areas for leaks ... no drips.
Switch ON engine ... Alarm sounded again.
What goes Wrong ?? where is the low level coolant sensor location ?
Also did a check on my control panel alarm wire connection ... no loose joint.
My Yanmar engine model, 6LPTA-STP 315Hp.
Whats your recommendation ?
Thanks n Cheers
Lawrento
Albin 28
RSYC
Singapore.

[johnmurray]

I have the same engine and I had a somewhat similar experience. Two years ago I was running the engine at high revs and the low coolant level alarm sounded. I stopped the engine and checked the coolant level, and it was down but still showing in the reservoir tank. There was no sign of any leakage. I added some coolant, carried on a more mderate revs and it has never happened again, not even at WOT.
My mechanic said it was normal to lose a bit of coolant due to evaporation, but he checked my cooling system anyway and found it operating properly with no leaks.