Thanks for all the feedback, I think I've covered most of the areas I need to to diagnose the engine.
I first saw what looked like steam when I ran it early one windless morning. It started to appear at about 1500 rpm
and got worse at 2000+ rpm
. I couldn't really see what the coolant level because I have no access from above the engine (it's under the galley
sink and counter). I only ran the engine for maybe 30 minutes, but during that time it did not run hot or overheat.
Here's what I did a few weeks ago:
1. I pulled the heat exchanger
and had the core
cleaned and pressure tested.
2. I re-assembled the heat exchanger with all new rubber boots, hose clamps, hoses, etc.
3. While I had the heat exchanger apart I pulled the mixing elbow and cleaned it. Then I remounted it with a new gasket
I then ran the engine in the slip up to 1500 rpms and didn't see any steam. The exhaust water is warm, not hot and the engine ran at normal temps.
Yesterday I dismantled the galley
in order to gain better access to the engine. So today:
1. I rented a cooling
system pressure tester and pressurized the cooling system to 7 psi. After 2.5 hours no change.
2. I cracked each of the hp fuel lines to the fuel injectors and noted a sudden drop in RPMs with each.
My plan for tomorrow:
1. Check the coolant level to see if it has changed.
2. Run the engine hard and under load for at least an hour to see if the coolant level changes and/or if the engine temp rises above normal.
I beginning to think (and hope) that it's either: a) steam caused by hot exhaust hitting moist cool air, or b) unburned fuel (probably caused by dirty fuel injectors or a thermostat that's stuck open). Either of those are a lot easier/cheaper to fix than a blown head