2007 340DA losing anti freeze

[Pierre Boivin]

Hi we are on a 3 week trip on the rideau canal in Ontario Canada. I noticed a while ago that the anti freeze in our port engine tank keeps going down after i top it up to same level as the starbord one. Engines are 8.1 Horizon. I have looked in the engine bay and cannot find leaks. There is no overheating, both running 160 degrees. Should i be concerned? where should i look next?
Thanks in advance

 

[scoflaw]

Probably going out the exhaust from a bad gasket but I would have the engine oil tested to be on the safe side

 

[Pierre Boivin]

thanks

 

[Pierre Boivin]

thanks