Date:         Tue, 16 May 2000 21:35:25 -0400
Reply-To:     John Lauterbach <jhlauterbach@EMAIL.MSN.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Lauterbach <jhlauterbach@EMAIL.MSN.COM>
Organization: Microsoft Corporation
Subject:      Re: Vacuum leak sources
Comments: To: Wolfvan88@AOL.COM

Robert, do you have part numbers and sources for the hoses and fittings that
are under vacuum?  I have been hoping that our list vendors would offer
"kits" as they have done for fuel lines and coolant lines.

John Lauterbach
'84 DL

----- Original Message -----
From: Robert Lilley <Wolfvan88@AOL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, May 16, 2000 10:33 AM
Subject: Vacuum leak sources


> Here are some areas to look for leaks.  Rubber parts are getting old and
can fail.  YOur engine might be "running good" but there could be a leak
going on.
>
> The following are various sources of vacuum leaks.  Once a leak starts the
engine starts to run lean, the O2 sensor will enrich the mixture to it max.
If the leak is more than the o2 max, the engine starts to run hotter and
further deteriorates the worn rubber parts increasing the leak and further
leaning the engine to the point of overheating and other running problems.
> When the engine is cold, the leak will cause the engine to stall because
the volume of air is to lean to support running the engine.  The idle
circuit is running in default with a set amount of fuel and ignoring all
sensors until it is warmed up.
>
> I discovered this be reusing the throttle body gasket after removing the
TB to adjust and clean it out and check the shaft air seals.
>
> It resulted in decreasing the amount of vacuum by allowing un-metered air
to enter the system.  The air decreased the amount of vacuum the engine
could build.  The following the effects:
>
> 1)  The cold idle cut off returned (I had replaced the idle control
module, $175, my Idle control module was damaged due to a short in the hall
sensor wiring harness)
> 2)  The amount of vacuum to control the fuel pressure regulator will
decrease.
> 3)  The engine can have a hesitation when the throttle was pressed.
> 4)  Increased fuel consumption.
> 5)  Poor running engine.
> 6)  Damage to the engine.
>
> Various sources of leaks:
>
> Air Runners:
> Intake gasket- head to air runner
> Small injector seals
> Rubber boots around runners and center plenum
> Leaks where the tube is pressed into the ends
>
> Center Plenum:
> Fuel Pressure Reg mount
> Throttle Body gasket
> Idle speed valve rubber boot
> vacuum line from fuel tank vent system
>
> Throttle body:
> Butterfly Shaft
> Seals on shaft cracked
> Vacuum for fuel tank vent system
> Air intake elbow
>
> Air intake elbow:
> Cracks in rubber tube
> Engine breather tube
> Idle control valve rubber intake tube
>
> Valves too tight:
> This causes a leak and decreases vacuum at idle and low speeds.