Date:         Fri, 11 Feb 2000 19:59:20 EST
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Re: coolant pressure gauge
Comments: To: wdavidson@thegrid.net
Content-Type: text/plain; charset="US-ASCII"

Bill,

Sorry that came across as so complicated. The reason I opted for the boost
gauge and its plumbing is that it reads both vacuum and pressure. I have not
yet found an affordable (<$450) electrical gauge that reads both pressure and
vacuum. If you are concerned about the ethylene glycol smell, and a possible
leak you can fill the segment of nylon tubing going to the gauge with
glycerine. Glycerine is available at any drug store. You just need to
evacuate the line to the gauge (after it has been installed to the gauge end)
and refill with the glycerine. Easiest way to do this is with a small bottle
with sealable plastic cap. Like the ones used for one man brake line
bleeding. Fill the lower half of the bottle with glycerine. Put two holes
through the cap. Put a rubber grommet in each hole through the cap. One of
these should have a 1/8 inch through hole in it and the other should have a
bore in it such that you can tightly insert a piece of rubber tubing. Put the
nylon gauge line into the 1/8 inch grommet hole and put the tubing end just
above the bottom of the jar, fully covered by the glycerine. Evacuate the
other hose with a small handheld vacuum pump (one man brake bleeder again) as
far as you can (gauge will read vacuum level of around 26 inches depending on
your location), then release the vacuum. The jar will refill to atmospheric
pressure and will force the glycerine to fill the volume of the tubing and
the gauge sensing tube. The surface tension and viscosity will prevent major
glycerine loss till you get things hooked up.

Don't use oil as it will coat the surfaces of the cooling system. The
glycerine is sufficiently miscible in water or ethylene glycol no damage can
be done. This "liquid filled" approach will give an even faster response to
the gauge than I now have.

The overall length from the coolant reservoir to the dash panel is around 14
feet by the circuitous route I chose. You could also plumb this into the
radiator with judicious choice of fittings at the bleed valve or one of the
radiator fan temp switches if you were more adventurous. Very useful. Easy to
track air pockets (max pressure when hot), leaks (obvious), real overheating
and consequences thereof.

In general the gauge response will grab your eye during mountain runs at full
throttle from 3000 to 6500 rpm. Not quite as interesting as the Exhaust
temperature gauge, but quite informative. I have planned a dump of gauge data
sets vs. load, power, O2 signals, etc. but haven't quite mustered for this
Saturday project yet.

Frank Grunthaner