Date: Fri, 22 Oct 1999 02:03:19 EDT
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: 1st Most important specialized waterleaker measurement device
Content-Type: text/plain; charset="us-ascii"
I must agree. Some time ago as Darrell and I were comparing notes and I was
installing my Digitool, he raised the issue of the coolant pressure gauge. I
purchased a relatively inexpensive turbo boost gauge from JC Whitney (fully
prepared for the worst). At about $15 dollars, and the same face size as my
VDO gauges it seemed a good choice. It has a 270 degree sweep and reads
vacuum (0-30 inches H2O) and pressure (0-20 psi) The gauge, like most direct
analog gauges, is based on a Boudon tube (bent copper tube spiral) driving
the gear mechanism turning the indicating needle. Therefore its fully sealed
and compatible with direct exposure to a water/glycol mixture. I used high
pressure rated 1/8 inch OD nylon tubing run from the engine area to my gauge
clusters. Works like a charm. I can follow the pressure rise on startup, the
change in pressure with load (7 psi cruising at 65, 12 psi going uphill at
full throttle), the point at which the cap vents to the overflow tank, and
the vacuum generated overnight as the system cools. So far, I consistently
see 1 to 2 inches of water (vacuum) in the morning, indicating the break
pressure for the vacuum vent on my cap.
For installation (on my '82 Diesel converted to '90 8 V Digifant inline 4), I
tapped a tube insert into the coolant tank level sensor and sealed it to the
sensor plastic with an epoxy fill. To this tap, I connected a 1/8 inch pipe
tee, ran one side to the gauge through an inline shutoff valve, and the other
through another inline shutoff valve to a 1/4 inch barb fitting. Then, to
remove air from the cooling system, I open this valve, draw a vacuum with a
vacuum pump working through a water trap. I evacuate the cooling system until
I remove about 20 cc's of liquid (and see the coolant hoses contract
somewhat) then close the valve. The air that is removed comes from the
cooling system, and when the actual pressure reaches a vacuum of more than
about 2 inches, the cap opens and takes in liquid from the overflow tank. I
then start the engine to circulate the liquid and let the pressure rise to
around 10 psi. There is an easily resolved pressure change when the
thermostat opens. After turning off the engine, I let the pressure maximize,
then vent to my water trap and draw a vacuum again. So far, this procedure
has removed all air pockets by the third cycle.
Just a final note on gauges. I modified the heater deflection shield to hold
two banks of gauges. The top row of three include a VDO Voltmeter, the
Turbo/Boost (coolant pressure) gauge and a 0-15 volt gauge from an Audi. The
first voltmeter is wired into the operating Vanagon ignition key switched
circuits and monitors the voltage in the dash area with ignition on. The
second Audi-derived gauge is wired to monitor the auxiliary battery circuit
voltage and is left on constantly. When parked or camping, a quick glance
tells me the state of the gel-cel auxiliary. When running, it gives me the
voltage at the terminal of the battery (equal to the output voltage of the
alternator). This lets me watch the voltage drop from the headlights, the 800
watt stereo, etc.
The second row of two gauges are VDO oil pressure and VDO oil temperature.
Over on the dash, I cut (whimper) two gauge holes, one on either side of the
steering column. On the left I have a VDO vacuum gauge (incredibly useful)
and on the right I have an exhaust manifold temperature monitor. In the
engine compartment, I have mounted three mechanical mini-gauges in a cluster
for simple diagnostics. These include an ammeter spliced into the alternator
output, a 0-60 psi pressure gauge plumbed into the test port on the Digifant
manifold for fuel pressure. This is also valved for safety. Only use it if
I'm suspicious about the F-I system, and an expansion bulb temperature
monitor which I have soldered into a copper heat sink (8x10 inches) mounted
next to the A/C compressor to monitor the engine interior temperature.
Finally, I have a diagnostic vacuum gauge and twist valve manifold on the
"firewall" so I can test the various vacuum signals during any testing or
tune-up adjustments.
Hope this is useful to someone.
Frank Grunthaner
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