[Vwdiesel] '00 Golf IP pump seal problem

[Tad]

Fascinating that there is so much detail behind a seemingly arcane and (per
the Cat example) sometimes disregarded bit of engineering.

Of course I exaggerate with the 50/50 comment, and an increase in bubbles
can indicate a leak, but in my experience you'll never get rid of all the
air and the system is capable of dealing with quite a lot of air before you
see any issues.  I could be wrong but it seems like it can take days before
the residual air is purged from the system after a filter change and you get
down to the "normal" small amount of trapped air.

But then again I'm still using the stock clamps, 10 years and numerous
filter changes down the road. :)

On Wed, Sep 7, 2011 at 5:47 AM, <pmdolan at sasktel.net> wrote:

> As Tad notes later, it is a matter of degrees, not absolutes.
> Unfortunately, this is a judgement call, but the fact is that suction or
> pressure, doesn't matter which, just pumping fuel through a fitting will
> released dissolved air.  It takes several thousand psi to put it back in
> solution (thus, why ALL non-common rail engines have timing errors while the
> air in injectors and lines compresses - and some engines - CAT HEUI in PSD
> installation - are so bad they will shift timing to way before TDC or even
> miss at idle on #8 - the so-called "cackle and knock" syndrome which is due
> strictly to incompetent management of the dissolved air released before the
> injector)
>
>
> On Tue, 6 Sep 2011 13:00:00 -0400 (EDT), lbaird119 at aol.com wrote:
>
>  Except that the bubbles are in the suction line, prior to entering the
> pump.  Sure,
> a vacuum will do (is essentially) the same thing as you described, there
> hopefully,
> isn't enough vacuum in the supply line or else the pump won't pump well and
> there's
> probably a restriction in the line.   In my experience, those bubbles come
> from leaking fittings/connections.  On the
> Rabbits, it's the hard line to rubber line, behind the fuel filter or the
> line itself, at the
> fuel tank.  On both Passats, it's been the thermo control on the fuel
> filter or the crimp
> fittings on the clear line itself.  Leaks between the crimp and the crimps
> and the hose.      Loren
>
> -----Original Message-----
> From: pmdolan
>
> To: vwdiesel ; Stephen Sherman
> Sent: Tue, Sep 6, 2011 4:41 am
> Subject: Re: [Vwdiesel] '00 Golf IP pump seal problem
>
> It is not likely that you have any air leaks.  ALL liquids stored in
> atmosphere have a tremendous amount of air dissolved within.  When you
> put fuel through pumps, fittings, etc. where the flow must cross or be
> forced around very sharp edges, the resulting low pressure releases
> some of that dissolved air, and that is what you will ALWAYS see in the
> clear lines of VW diesels.  Think about pictures of submsarines or
> even props on regular surface vessels - they always have a trail of
> bubbles coming from them. That is dissolved air being released from air
>
> (and why it is so difficult to make a submarine quite - when those
> bubbles implode them make a very loud noise that is easily detected by
> sonar - and that same implosion is so violent it blows little bits of
> metal off of propellors and impeller - called cavitation wear. I could
> write a book about which diesel engine designs don't work as intended
> because they don't deal with dissolved air properly/  And, yes, in
> case you are wondering, this is one of the things I do for a living -
> make equipment to remove dissolved air from oil).
> On Mon, 5 Sep 2011 21:22:56 -0600, Stephen Sherman  wrote:
>
> Well a bit more as things unfolded...
>
>>
>> Car drove well for a week, then one day I noticed a strong fuel smell.
>> Looked under the hood, and the IP was leaking from the seal below the QA.
>> Pretty obviously that gasket from the wet area and dirt.  Order the gasket
>> kit and special tool, and replaced that and the top cover gasket. Got the QA
>> adjustment back into the working range (good idle now), and things seem OK.
>> At least no signs of new fuel leaks around the IP.  Definitely would suggest
>> multiple alignment marks if you do this, as I needed to rely on a second set
>> to get the QA in spec. (The epoxy chipped off as I took it apart, so wasn't
>> able to use those marks)
>>
>> Still have some air leak, as I can occasionally see a stream of bubbles in
>> the fuel clear line. Hoping its not one of the IP gaskets I replace. Will
>> replace the injectors furl return line as it is getting pretty old. And take
>> a closer look at the main return and fuel lines. But at this point, the only
>> symptom is the air bubbles in the fuel line. No obvious leaks anywhere.
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>>
>>
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