Volvo MD2020 - Found coolant in our bilge

[dwwilde]

We have a 2002 Volvo MD2020 w/ Sail Drive. This past winter, we had the sail drive seal replaced (routine maintenance). Engine had to be unbolted and moved to allow this.

Recently, after motoring at ~ 3000 rpm for ~1 h, I noticed our bilge was laden with green antifreeze coolant. What does this mean?
I had no overheat alarms (however, I do not fully trust the "idiot lights" on our indicator panel). I had topped up the heat exchanger reservoir with Volvo coolant prior to this event.

Question: What could this mean?
Possible options:
1. Could this mean exhaust gases entering the heat exchanger? If so, how do I test for this?
2. If the thermostat was not opening, could this result in a boil over? Even if I had not seen an alarm or indicator light?
3. Could this simply be a case of the coolant equalizing its volume after I had topped up the exchanger?

The engine has no coolant overflow reservoir, so any excess goes into he engine bilge.

Advice is welcome.

[JimsCAL]

Is the coolant level now OK? If so, it sounds like it was just overfilled when cold and then expanded when the engine was run. Can you retrofit and expansion tank?

[dwwilde]

Thank you. The maintenance manual I have shows a rather unclear diagram that suggests that when the coolant is at the proper level you can see the "level spur". When I had topped up the coolant, I simply added until I could see fluid inside the filler hole. Now, I can see metal structures inside the filler hole, which is the way it has always appeared.

I am certainly hoping it is simply a case of overfilling and equalization. My mechanic has suggested an alternate possibility (less desirable) is that the exhaust gases are getting into the heat exchanger at the head. I cannot test for this as it requires a special device to pressurize the exchanger.

[Faster]

Another vote for simple overfilling. On our bowman heat exchanger the recommended (cold) level is less than a full reservoir, and we have an expansion tank as well to catch any release.

You should be able to add an expansion tank by adding a hose and small tank/bottle (from an autowrecker, perhaps?) to the fitting under the cap from where you likely 'overflowed' to the bilge.. there may already be a hose on that.

[bandaidmd]

A buddie of mine that owns a radiator shop taught me a quick test to check for head gaskets pressurizing the coolant system. Start a cold engine and run at a fast idle for 40 seconds and shut it off, now remove the radiator cap and if theres pressure you most likely have combustion gasses entering the coolant system. By only running it for 40 seconds any pressure build wont be from heat expansion.