Couldn't you place an exhaust gas sniffer in the coolant tank to smell for exhaust and accomplish the same thing?

I'm having a similar problem with my engine with 212,000 miles on it, and it is pretty clear with the great gouts of steam that pour out of the exhaust, that water is getting into the combustion chamber.
The interesting part is that there are no coolant leaks outside the engine, and no evidence of oil in the coolant. (coffee-colored blobs.)

Todd

----- Original Message -----

From: "Dennis Haynes" <d23haynes57@HOTMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Tuesday, September 29, 2015 1:25:52 PM
Subject: Re: Missing coolant

If this is a problem you may also find a damaged piston and cylinder. BTDT
more than once!

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Stuart MacMillan
Sent: Tuesday, September 29, 2015 12:20 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Missing coolant

Not a pleasant thought. I'll see what happens.

Stuart

-----Original Message-----
From: Dennis Haynes [mailto:d23haynes57@hotmail.com]
Sent: Monday, September 28, 2015 10:08 PM
To: 'Stuart MacMillan'; vanagon@GERRY.VANAGON.COM
Subject: RE: Missing coolant

You may have a head cracked in one of the exhaust ports. Pressurize the
cooling system and let it sit overnight under pressure. If you get a big
cloud at start up there you go.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Stuart MacMillan
Sent: Monday, September 28, 2015 5:11 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Missing coolant

Just when everything seems to be sorted out, it isn't. Son's '87 is losing
over a quart of coolant every 400 miles, and I can't find any leaks. Rear
heater has been removed, and there is no odor from the front heater. No
drips anywhere-engine plumbing, heads, transmission cooler, radiator, or
front heater valve. No evidence of coolant mixing with either the
transmission fluid or engine oil, and that much coolant would certainly foam
oil.

I'm wondering if it's burning coolant, but in my experience failed sealing
rings in Vanagons lead to over pressurization of the system, and that's not
happening. It also runs great. I sometimes notice a faint smell of burning
coolant at the engine compartment vents, but I can't find anything dripping
on the exhaust when the system is pressurized.

Would investing in a UV leak detection kit tell me anything? It would seem
losing this much coolant would show up somewhere.

Any ideas?

Stuart