Old hoses leak microscopic amounts of coolant. Ive had it spray onto the
engine in such small quantities that it would evaporate before you could
see it. Tighten hoses, replace hoses is about all you can do. But you
didn't mention testing the pressure cap. That can send a good deal of
coolant into the expansion tank, which can drip on the road through the
overflow and you won't know it.

Jim

On Mon, Sep 28, 2015 at 4:11 PM Stuart MacMillan <stuartmacm@gmail.com>
wrote:

> 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
>