Date: Thu, 3 Oct 2002 12:28:25 -0700
Reply-To: Stuart MacMillan <macmillan@ATTBI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stuart MacMillan <macmillan@ATTBI.COM>
Subject: Re: Does a worn pressure relief valve cause Oil pressure buzzer?
In-Reply-To: <3D9C8E31.FB319BA7@highspeedplus.com>
Content-Type: text/plain; charset="us-ascii"
-----Original Message-----
From: Mark Keller [mailto:kelphoto@highspeedplus.com]
Stuart,
Thanks for the info. Is the relief valve cylindrical or spherical? My
thoughts were that a cylindrical valve with wear could flutter stick or
operate slower when the bore was heat expanded OR a spherical type could
have
bad seat or crack seat, or a wear deformity in the ball surface.
It's a cylindrical piston. It is pretty bomb proof.
I hadn't considered a broken helical spring, but a weak helical spring, and
thin oil at high temps and wear could be an issue. If I turn the key off
and
immediately on the issue does not repeat usually. The last time thought it
triggered several times. What I'm not telling you though is I have a Gulf
Coast submicronic filter which taps via a TEE to the blue sensor pressurized
port between the push rod tubes. On occasion, and this is one, the filter
element, toilet paper will not be dimensionally as large as other TP rolls.
Scott 1000 single ply is the recommended media-- but seems unavailable
here.
I'm using Scott 500 two ply, but there is a difference in the paper. My
suspicion is that while this filter system isn't the total culprit, it adds
it
bit of pressure loss.
Oil filters should be installed right at the pump, yours could lower
pressure depending on where the oil reenters the engine. I'd re-do this by
installing a bypass filter system that replaces the stock oil filter. I've
done this, but use the Trasko, which has "special" Japanese mini toilet
paper rolls. Actually, they claim to be special, and that fibers can slough
off of supermarket tp. Check out Trasko at www.trasko-usa.com. I've been
impressed with this filter over the last two years I've used it.
Also has David just pointed out to me, overfilling exacerbates the heat
issue.
I'm currently overfilled, as I mentioned the sub micronic canister, at times
getting the oil level is extremely tedious and I just let stay high level
and
burn off. So I'm sure the engine was on the high end of the temperature
scale
when I did a 5 minute mountain climb at max power of 4400 rpm , second gear
in
the automatic with the van carrying 1500 lbs of payload. Just after crested
the
top and let off and the engine rpm dropped to 3200 and 3rd gear then I got
the
buzzer. Key off then on, and no more alarms until an hour later.
I've never had a problem with overfilling, but it could cause problems. I
still can't see running below the normal notch on the dipstick though.
However, I believe I read from David Beierl, that the circuit is designed
with slope sensing, i.e. if a drop or increase is of such a velocity that
the
tolerance would be exceeded, then the circuit arms. So the circuit could
easily "jump the Gun" if a slow pressure valve or sudden drop in rpm causes
a
quick drop in oil pressure.
I did note in your post that the High pressure sender port is upstream of
everything, so a fluctuation at that point could come from the pump or
something downstream letting the pressure out. Is the oil pressure relief
valve just downstream from the .9 bar sender or just before it?
They are essentially in the same place, but the relief is before the filter,
so if it gets plugged it will open. That's why oil filters need a bypass
valve in case the filter plugs, without one the engine bearings will be
starved.
Also you mention the removal and replacement needing a special tool. Is
this a
KD or Liesle, or a VW source. Looks like this cover plate plate on my
engine,
near the dip stick entry is weeping oil as well.
I got mine from my flaps, I think is a KD, and was under $10. It's just a
disk with a 3/8" drive hole and a ridge that fits the entire slot on the
relief plug (it's a big screw on the bottom of the engine). That leakig
plate is the oil pump cover, and in my experience they all weep a bit sooner
or later. Forget about it.
I think the real issue seems to be that a mass market synthetic like MOBIL 1
is
not the best choice given high time motors and the thermal expansion of the
alloy case. I've used REDLINE and it seems thicker, at room temp, I wonder
if
really we should just avoid the mass market synthetic and stay with a
premium
synthetic , especially for an over 100k engine. Mine uses no oil, is strong
and has virtually rock steady 13.5" vacuum at idle. I have "vaporized" oil
consumption with the thinner synthetics .
Modern engines are high precision machines, and manufacturers like the thin
oils, they raise the MPG a bit, and flow quicker at startup. Our WBX
engines are just not designed for these oils.
Stuart MacMillan wrote:
> Mark,
>
> This is pretty unlikely, but possible. It would take a lot of grit in the
> oil to wear the valve enough to cause this. Usually relief valves stick
> closed, but springs can break too. It's an easy replacement (buy the
proper
> tool, it's cheap) if you want to try this, but if you find a very worn
> relief valve then your oil pump is shot too, since it pumped the same
grit!
>
> Unfortunately, the WBX is not a very tight engine under the best
conditions,
> and the expansion of the alloy case causes oil pressure to drop as it
heats
> up, further opening the already loose tolerances. Since it is the main
and
> rod bearings that affect oil pressure the most, as they wear you start to
> see the pressure drop, and this is more pronounced the harder the engine
> works. The rod big ends start to get oval with use, and this is probably
> the main cause of low oil pressure. See my article on Tom's pages:
> http://volksweb.relitech.com/21rodbrg.htm
>
> The new sender at the oil pump measures the highest pressure the pump can
> deliver, and everything else downstream gets less. The sender between the
> pushrod tubes measures the pressure at the main bearings, where the most
> severe loads are, and this is where the gauge should be installed.
Further
> downstream are the lifters which need oil pressure to maintain zero lash,
> and through them oil goes up the pushrods to lube the rockers. The
lifters
> can normally drain down after periods of sitting, and should pump up
> immediately if oil pressure is good. Quite often they can take a few
> minutes of running to do so, every WBX I've owned as done this
occasionally.
> Marvel Mystery Oil can help this, as it is a solvent that can clean out
> "stuck" lifters. Much is in the archives on this.
>
> Get a gauge and remove the uncertainty of your situation. As a quick fix
> try mineral 20w 50 oil, the synthetics are physically much thinner, and
this
> can have a dramatic effect on the WBX oil pressure.
>
> -----Original Message-----
> From: Mark Keller [mailto:kelphoto@highspeedplus.com]
> Sent: Thursday, October 03, 2002 8:03 AM
> To: Stuart MacMillan; Vanagon Mailing List
> Subject: Does a worn pressure relief valve cause Oil pressure buzzer?
>
> Stuart,
>
> I am having this issue on occasion, with similar conditions: heat
> soaked, i.e. long climb, Mobil 1 syntheitc and get the buzzer just after
> letting off of the throttle, i.e. cresting the hill. I'm also having
> very infrequent but associated with the buzzer episodes a split second
> valve clatter like once a year, but it will happen two or three times
> then not again for a year.
>
> Can you shed any light on the possibility of these events being caused
> by a worn pressure relief valve.
>
> Sincerely,
>
> Mark Keller
> 91 Carat
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