Here is what I know:
Engine is a 14 year old Yanmar 4JH2E with 2000 hrs.
- Earlier in the season the engine would use a few ounces of coolant when I ran it about an hour or 2
- Now suddenly the coolant is disappearing at the rate of appr 64 ounces per hour
- No sign of coolant in the oil.
- No sign of oil in the coolant.
- No sign of coolant in the bilges or under the engine.
- Engine otherwise runs perfectly. Good power and smooth operation. Starts on first try.
Last night I performed some diagnostics with a pressure tester. Here are the results:
- Engine off, system pressurized to 16lbs, tester slowly lost pressure. Started the engine and AF came out the exhaust
. Took a few tries to start.
- Refilled system, connected tester, started engine. No jump on the tester. If the gauge suddenly jumped up it could indicate a head gasket problem.
- Engine running, pressurized the system to 16lbs and needle did not jump around. If it did it could indicate cracked head or block. System slowly lost pressure.
I am thinking bad heat exchanger. I will pull it tonight to check.