[C38] Water Heater Plumbing

[david at dlrfilms.com]

> After years of chronic engine heating problems, I asked this C-38 forum
> for suggestions.

I guess it's my turn.

We had now heating problems when we bought the boat, but last Summer
started to get overheat alarms.

Simply cracking open the system to check this and that seemed to clear it,
so I have (hopefully) deduced that it is an "air-lock" problem.

But the overheats have gotten more frequent and are less reliably cleared
by cracking open the system.

Our most recent fix it to take the hot water heater out of the loop, which
works, but I can still see the air-lock forming, but without the hot water
heater in the system there seems to be enough circulation pressure to push
past it.

Because if the deteriorating nature of the problem I am wondering if the
freshwater impellor might be damaged, but when I start the engine with the
cap off the coolant tank, I can see (what appears to be) vigorous flow.

It also seems like maybe the cap, which is spring-loaded and leads off to
the overflow tank might not be working right. When the air-lock forms it
pushes the coolant back down the tube, but my intuition is that this
should function more like an air-release valve. But I'm not an engine guy
in any way, so not knowing what it's supposed to do, I don't know whether
or not it's working right.

I'm half hoping the whole thing will overheat and seize so I can put in an
electric drive.

Help?