Jack,

Have an exhaust gas test kit and then use it to test the coolant for
exhaust gases.  If you detect exhaust gas in the coolant then shut down
the van.  Now you want to unplug one spark plugs and do the test again.
Do this for each cylinder in turn.  The cylinder or cylinders that, when
you unplug them, you get no exhaust gases in the coolant with your
tester are the offending cylinders.

That said, if it were me and I had an exhaust gas leak into the coolant
system, I would do both sides of the gaskets at least and if I saw a
crack between the valves I would replace the head as well.  It is just
not worth it to do just one side as the extra time to do both heads is
less than two hours, the real time consuming part is stripping the
engine down enough to do the heads and you really don't want to do that
again any time soon.  Do it right, do it once, and enjoy driving your
van is my moto.  If you need anything please consider us.

--
Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: 856-327-4936
Fax: 856-327-2242

On 11/9/2010 12:47 PM, John Mosley wrote:
> what is the easiest way to determine which cylinder is leaking exhaust gas into my
> coolant system?
>                      thanks
>                                  jack     91 vanagon auto  gl
>