02 Westerbeke 7.6BTD genny slowly losing coolant

[aquadancer]

My 2002 Westy 7.6 BTD with approx. 600 hrs on it has been slowly losing coolant this season. Expansion tank goes from "full" mark to nothing over about 15 hrs of use.

No obvious leaks on the outside, oil looks and smells normal. Running temps are normal and steady.

I had 500 hr service done by Westy tech at the end of last season which included valve adjustment and cleaning the heat exchanger. Seems like coolant loss started after the service was done.

Any ideas / suggestions for checks?

 

[Turtlesboat]

You should have the heat exchanger pulled and pressure tested to make sure you aren't loosing it from there.

 

[aquadancer]

Thank you, Turtle... no external leaks, oil clean and level not increasing so I think you're right, most likely a small leak in the HX. Guess I'm gonna sqeeze in there with radiator pressure tester, take the end cap off, pressurize the coolant side and see what happens...