Take a good look at the top of the t-stat housing. See where the crossover
pipe from the right head and that short hose to the left head attaches? The
small disc on the t-stat closes that port as it opens the large disc to send
coolant to the radiator.

Yes, the 2.1 cooling system has a few more hoses. The major difference is
that the engine and heads are completely self bleeding. In the events of
leaks, it can recover on its own much easier then the 1.9 system. Even small
combustion gas leaks can burp out on their own. You can change a water pump
and without opening the radiator bleed, 2 or 3 heat cool cycles will get it
going. I had customers where the bleeder on the radiator pulled out and I
melted, sealed it over. Got the system going even after a head gasket
change. VW must have seen the need for the design change.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Benny boy
Sent: Wednesday, February 07, 2007 9:49 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Need input on radiator problem

"""the lower disc closes off the bypass that allows coolant to continuously
flow throughout the engine.""""
Not on the 1.9L Dennis, i have a 1.9L WP housing in my hand, and i don't see
how this could happen, i agree on the 2.1L. As for the 1.9L coolant
circulation in the water jacket, i agree, but i did some test on a 1.9L
(brother in law) putting an Aircool head temp thermo coupler on each
cylinder... the funny thing is that #2 and #4 where slightly hotter....

Now, what about joining the left head front output to the outgoing (going
front) main line????

Anyway, we will see as i'm putting an extra coolant temps sender on that
"blocked" left front outlet plate (on the head), i will be able to switch
with the original one. I like the simplicity of the 1.9L cooling system, les
 possible leaks...

Cheers
ps.: no news yet

--------------------------------------------------------------------
The engine can run hot without a thermostat. As the thermostat opens to
allow coolant to flow from the radiator, the lower disc closes off the
bypass that allows coolant to continuously flow throughout the engine. So
the flow to the radiator is basically short circuited without the
thermostat. If the even is an automatic, it is even worse as the trany oil
cooler is a parallel loop with the radiator always taking some of the
available flow. Then to make matters worse, the 1.9 cooling system does not
flow coolant through the engine. The in and out are both on the rear. The
water jacket being filled and convection cool the front cylinders. With the
heater valve open, coolant then flow through the right side of the engine.
Not left front outlet is there unless someone added it, (easy to do). So it
is possible to have a good gauge reading and still be overheating the right
side if vapor bound or something.

Dennis