Larry,

I specifically wanted to monitor the pressure at the coolant tank to follow
the amount of air trapped and the measure the negative pressure on
acceleration of the engine. There is a significant pressure drop from front
to rear caused by flexible hoses in the line and losses across the radiator
and heater core.

Anyway, either approach is interpretable and provides valuable information.
Darrell went to the front, I went to the rear. You takes your choice ...!

I have had several anomalies that I think would not have been traceable from
a frontward approach:

1. Air in coolant reservoir.
2. Proper seal for vacuum evacuation of liquid from the overflow tank to the
reservoir. I usually see 1 to 2 inches before the cap opens at 5.
3. Coolant tank dropped out of holder and hung by hoses in the bottom of the
engine compartment. Upside down. Interesting readings.

Frank Grunthaner