Espar Hydronic 4 coolant leak/pressure/bleed question

[brianc]

Last year I posted about the expansion/holding tank in my Espar Hydronic 4, and ultimately we had the plastic "overflow" tank that was leaking with a proper metal expansion tank. Everything worked fine.

Last week the header had trouble starting, exhibiting a similar pattern to what happened when the coolant leaked last time. Today, same behavior, so I climbed in to the lazarette to check it out. Sure enough, it's leaking again, but from the coolant out connection.

I don't think it's had enough failed start cycles to lock itself out yet so I thought I'd try to fix it myself (this heater has cost me more than any other single item since I've owned the boat!)

Attached are pictures.

I generally know what to do but not necessarily how...close valves on coolant lines, remove/replace section of hose and clamps, refill coolant to recommended level, and bleed the system. So I have some questions I'm hoping someone can help me with!

1. What is the correct coolant fill level (assuming I add coolant to the overflow tank?) I've seen this level mentioned but no one has said what it is.

2. How do I bleed the system? I know where the bleed screw is but I'm not sure of the procedure. Is it the typical open the bleed valve and start the heater, then close the valve when air stops coming out?

Any help would be greatly appreciated!

Thanks,
Brian