Yanmar 6BY2

[Andrija]

Does anyone know how to properly bleed the cooling system after changing the antifreeze on a Yanmar 6BY2 engine? I am having major temperature problems after changing the coolant.

 

[scross]

Did you burp it? That is, run it and recheck the coolant levels? We had a similar problem with our 4BY2-150 when our “professional” marine shop took out 4 gallons of old coolant, filled it “full” and didn’t burp. After a test run it was getting a bit hot we took the boat back to the shop. The “professional” ended up adding almost a full gallon more to get it full to the cap level.
PS Don’t trust the side overflow lank to tell you the engine coolant is full. The overflow tank is NOT a good indicator of the coolant being full.

 

[Andrija]

We tried everything, this is 6BY2 and its thermostat is probably in an awkward place, so after several attempts at irradiation we were unsuccessful. An additional problem is the boiler on that side of rhe boat.

 

[CaspersCruiser]

PS Don’t trust the side overflow lank to tell you the engine coolant is full. The overflow tank is NOT a good indicator of the coolant being full.

In my experience with a 4BY2-180, that’s good advice. The coolant tank is completely useless to determine coolant level, despite being placarded as such.