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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
Comments: To: jneal@netcom.com
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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