I think you are right about the cap.  It appears now to just let coolant flow back and forth cycling from idle to higher revs.  I have one on order.

 

Stuart

 

From: John Rodgers [mailto:jrodgers113@gmail.com] 
Sent: Monday, September 28, 2015 2:45 PM
To: Stuart MacMillan; Vanagon mailing list
Subject: Re: Missing coolant

 

Stuart, the key here is in the way the expansion tank works. If it's the heads, combustion gas pressure will empty the expansion tank into the over flow tank when its warm, and all will appear normal, but when the engine cools, it will not draw collant back into the tank. Also, you may have a miniscule crack in the plastic that only opens up when warm. And finally, if a tiny leak only occurs when the engine is warm, and mskrs it's way to the exhaust somehow/somewhere, it will eveporate by the time you can stop, shut down, an look/see. BTDT!

  -John 

On Sep 28, 2015 16:11, "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