This may or may not help you out, but I had a similar situation with a 1.8T
installation.

 The first issue was the use of a cheap thermostat. The cheap thermostat
would stick wide open. It would work fine sometimes, but other times it
would stick. I switched to an OE thermostat from the dealer and that problem
was fixed.

 I also had a hose routing problem that caused some erratic cooling
behavior. I designed and built the entire 1.8T installation myself. I copied
the Audi cooling routing to a T which has the expansion tank return hose
plumbed into the main coolant return (to the engine) hose. In this
configuration, the thermostat acted very erratically. Moving the expansion
tank return hose to a T in the heater circuit return hose solved the
problem. The temps are now 100% predicable and steady.

 So I only bring the hose routing thing up because I wonder if you have a
hose (or two) routed incorrectly.

Thanks,
Christopher
www.t3technique.com

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Jim Felder
Sent: Thursday, December 10, 2015 10:22 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Sick sick sick of diesel Vanagon cooling problems

Two weeks ago I completed the conversion of my diesel Vanagon Westy turbo
diesel over to the new style tank with new engine hoses. As I write this I
am sitting in a Hardee's parking lot waiting for about the 15th time in the
last two weeks for my engine temps to go down to the point I can drive the
car. Before I left home for the short drive, I bled the cooling system
according to the Bentley for the eighth or 10th time since making the
conversion. I have only managed to have heat from the heater once or twice
in the last two weeks. I am on my second blue coolant In that time. When I
wake up in the morning I check it first thing. Always there is considerable
pressure left in the system from the night before. I installed a new
thermostat. I tested the old thermostat and the new thermostat on the stove,
and they both operated exactly the same. I put the new one in anyway.
Usually I can drive somewhere as to a store maybe 4 miles away. Going to a
store or on an errand it's likely to run just fine with the needle steady in
the center all the way there. Then on the way back I typically have to pull
over just like I have done now. I can let it cool down maybe leasing the L
some air out, and then be on my way with a slightly hi or sometimes normal
temp gauge. I never know what to expect. But no longer can listen to audio
because I have to keep my attention riveted on the temp gauge. It's not
leaking. I'm not losing coolant. I just can't get rid of this air bubble. I
don't think I have a leaking head gasket because yesterday I drove to a town
100 miles away and back without really having any problems. There are some
steep hills along the way. The temperature stayed normal. I don't find any
soot in the coolant or water in the oil.

Any ideas? The temps were perfect before my "upgrade."

Jim