It's a very quiet listless night. In Grace's cockpit I'm wondering about my engine once again.
The morning after I wrote Update 03 I found the water level to be low. We had lost water again. But something was different this time. I saw a leak! Water was dripping from the connection between the heat exchanger and the circulating pump. One of the O-rings sealing the joint had failed. I was elated. Here was something I could see and fix.
I tore down the engine one more time, replaced all the O-rings connecting the heat exchanger to the rest of the engine. When everything was back together I ran the engine for a couple of hours. It held it's water.
This morning we took a two hour test run. The water level is holding ok. Not perfectly the same, it is a little bit lower, but close enough to be within my margin of error.
Tomorrow morning we will take another test run.
I've started checking the weather again.