[Vwdiesel] Brake boost failure.... Lazy pump Update.

mark shepherd mark at shepher.fsnet.co.uk
Sun Dec 21 19:31:36 PST 2008 

New update on lazy pump:

 I cured the vacuum leak showing on the gauge. This appeared to be in the 
join of the tubing leading into the car. So now gauge holds pressure for 
hours. Thus, braking system good and both oneway valves good.

I stripped the pump down, as far as easily achievable. [ Lid off pump out, 
and vanes out.]
http://img67.imageshack.us/img67/8562/vacuumpumpah0.jpg
http://img78.imageshack.us:80/img78/4862/vacuumpumpcloseupwb3.jpg
The two seals under the 'foot' of the pump seem fine.
Seal under the barbed lid looks a little poor; but is still standing proud 
of its recess and soft enough to be sealing. Gauze in middle of pump hides a 
tube down through and apparently open to sump. It was not blocked. I rinsed 
the pump out with gasoline. The vanes are of carbon type material... In fact 
I'd go so far as to say they look more of a brown bakalite to me. They have 
slight wear, and some pitting.
http://img389.imageshack.us/img389/6167/pumpvaneiz4.jpg

Their edge is essentially semicircular, and not contoured to the shape of 
the pump bore. They weren't excessively sticky, but then again being almost 
weightless, probably not much needed to restrict them. After cleaning, they 
were loose in their slots. I decided because of afore mentioned shape, that 
it would be fine to reverse them, [trailing edge to chip free leading edge].

Reassembled pump started car up and immediate response. Left overnight and 
then popped out in morning on Saturday. Drove about 1/2 mile... Nothing. I 
parked up and shopped and came out again. I slackened the three lid bolts 
slightly and then started the engine. Immediate steady vacuum  rise to about 
20" wg [23" but flickering previously] I retightened the bolts and vacuum 
remained. Pump body was warm to the touch. This must be the answer, the pump 
[vanes] must be binding until somewhere near blood warm.  If you look back 
at the lid under the vane picture; interference marks from the pump rotor 
can be seen. If the vanes are also touching the lid then they wont open 
IMO... [Look how the vanes point like cords, rather than radially, which 
mean they retract when they meet resistance and so, I guess less chips per 
year ;o)] Pump worked fine for rest of the day... I must find a way of 
reducing interference... I'll sleep on it...

Saturday evening, I'm looking at how to quieten down the engine which seems 
to have become noisier than usual these past few weeks. Sump pressure may be 
slightly worse than recent times. oil droplets splashing around slightly, 
but oil baffle restricts view. Revving engine up and sump pressure drops off 
as perceived  through the oil filler hole. I'll just check the oil level....

Holycrap the oil is off the dipstick and requires a pint and a half or more 
to get it back to it's correct level. H'mm no warning lamp. Engine off, 
ignition on... Still no oil light... heck... I wonder how long this has been 
the case...  I know only last month I checked head pressure and got about 
25psi fully hot at idle, with 50+ at 200rpm. Topping engine up reduced some 
of the noise. Ticking sound that I've had for a year, receded to it usual 
level.  A friend's wife last week had  asked me if the engine was clockwork 
:o)

Sorry about the essay, BUT, now for the interesting part...

 After topping oil up, I noticed the brake vacuum rose to 28" wg [up from 
the 'newly bedding in' reversed vanes value of 20"] Now this is even more 
interesting....
Sunday morning:
The gauge showed buildup of vacuum immediately. A lovely 28" wg. I did about 
4 miles, and gauge barely dropped with single applications of foot pedal 
yipppeee!!!  The next few days will provide the proof of cure...

My new questions might include; maybe the pump has the need for more than 
just vapour, thinking laterally, you might kill a pump if you used total 
seal otherwise!!!! The vanes fling out and in rotating squeeze the air out 
of the servo/booster line, and push it out of a drain on the side of the 
pump, but looking at the action of what is effectively a spinning disc on 
the side of the vanes, which my physics tells me creates an increase in 
pressure radially as the film of oil moves outwards and actually sucks oil 
up the centre past the gauze. Close inspection of the picture of the face of 
the rotor of the pump shows a recess that acts as an oil reservoir. So this 
then is spun out radially and drops in the gaps of the rotor behind the 
vanes and out at the bottom end too, keeping everything nice  for what is 
now 23 years for this particular engine... I don't suppose that the Quantum 
Bentley presently winging it's way across the pond towards me explains all 
this, or does it ;o)

Essay over....
Mark



----- Original Message ----- 
From: "mark shepherd" <mark at shepher.fsnet.co.uk>
To: "vw fans" <Vwdiesel at vwfans.com>; <brian at gochnauer.net>
Sent: Friday, December 19, 2008 3:06 AM
Subject: [SPAM] Re: [Vwdiesel] Brake boost failure....Update.


>
> Ah...
> As I've mentioned before, between inline valve and servo/booster, it
> basically holds, but where I'm measuring, the little barbs, vacuum lasts
> only a minute. So there must be a leak, that matters. There must be a
> second[third  in total] oneway valve in the pump. Is it imbedded below the
> gauze in the 'drive shaft'? ... It must be nest pas?  If that was
> clogged...H'mm as long as the vanes seal on the lid, and the large barb
> seals, wouldn't pump still work? Maybe its the slightly leaking large 
> barb?
> Tomorrows going to produce answers I hope, or at least after Saturday's
> morning start.
> Thanks for your help; it's nice to have a mystery to solve...
> Mark
>
> ----- Original Message ----- 
> From: "brian gochnauer" <brian at gochnauer.net>
> To: <vwdiesel at vwfans.com>
> Sent: Friday, December 19, 2008 2:45 AM
> Subject: Re: [Vwdiesel] Brake boost failure....Update.
>
>
>>
>> It's a vacuum pump, if the shaft seal is bad, wouldn't it just 'suck' the
>> oil in.?
>>
>> On 12/18/08, mark shepherd <mark at shepher.fsnet.co.uk> wrote:
>>>
>>> I'm sure the problem points to sticky vanes. If it is the oil, then I
>>> wonder
>>> if it's a residue buildup over a period  of time, or, an increase in 
>>> sump
>>> pressure creating an excess of oil?
>>> I will give the vanes a clean. My sump pressure is significant, but with
>>> increase in revs all but dissappears, which makes me feel rings not all
>>> that
>>> bad., and not noticeably changed since last gasket change 6000 miles
>>> ago...
>>> If the pumps wear, then I assume vane faces would wear a little and 
>>> slide
>>> easier if operation based on centrifugal forces. H'mm the arrows are
>>> pointing to sticky residue, releasing when warm...
>>> I'll clean tomorrow [today].
>>> Mark
>>> ----- Original Message -----
>>> From: <decker at toledotel.com>
>>> To: "mark shepherd" <mark at shepher.fsnet.co.uk>; "vw fans"
>>> <Vwdiesel at vwfans.com>
>>> Sent: Thursday, December 18, 2008 4:09 PM
>>> Subject: Re: [Vwdiesel] Brake boost failure....Update.
>>>
>>>
>>> >
>>> > Hi Mark;
>>> >    I have never had a problem with a vane pump. I grab one whenever I
>>> > can
>>> > find one. The diaphragm pumps work but even when rebuilt seem to be a
>>> > problem later down the road. I have never taken a vane pump apart
>>> > because
>>> > I
>>> > have never had one fail. I would think that unless one is just plain
>>> > worn
>>> > out the only thing that might cause a problem is sticking vanes.
>>> > Perhaps
>>> > taking it apart and cleaning it in carburetor cleaner or a hot tank
>>> > might
>>> > help. I'm completely shooting in the dark since in my experience they
>>> > always
>>> > work. If any of my friends find out that I have bought a parts car 
>>> > with
>>> > one
>>> > in it they practically fight over the silly thing
>>> > Brian Decker
>>> > Western Washington
>>> > ----- Original Message -----
>>> > From: "mark shepherd" <mark at shepher.fsnet.co.uk>
>>> > To: "vw fans" <Vwdiesel at vwfans.com>
>>> > Sent: Thursday, December 18, 2008 4:07 AM
>>> > Subject: Re: [Vwdiesel] Brake boost failure....Update.
>>> >
>>> >
>>> >> OK today's [Thursday] report:
>>> >> Temperature this morning 5 to 10  deg C. Upon starting the car and
>>> > operating
>>> >> brake, gauge rose to about 5" WG, and then died. Revving engine did
>>> > nothing.
>>> >> Possibly residue escaping from last night?
>>> >> Vaccuum began appearing within about 1/4 of a mile of yesterday's
>>> >> point
>>> >> [before it].
>>> >>
>>> >> Been good all morning. 'RH Turn' effect may just be nothing.
>>> >>
>>> >> The opened out pump couldn't be simpler; but does any one have an
>>> >> accurate
>>> >> description?
>>> >>
>>> >> For example, apart from centrifugal force, does the oil actually 
>>> >> force
>>> >> the
>>> >> vanes apart, or is it just a lubricant?
>>> >> I guess I'll have to run it with the lid off and watch for a fountain
>>> :o)
>>> >>
>>> >> Farmer Joe  have you cut one open? LOL
>>> >>
>>> >> Mark
>>> >>
>>> >> ----- Original Message -----
>>> >> From: "mark shepherd" <mark at shepher.fsnet.co.uk>
>>> >> To: "vw fans" <Vwdiesel at vwfans.com>
>>> >> Sent: Thursday, December 18, 2008 3:22 AM
>>> >> Subject: Re: [Vwdiesel] Brake boost failure....Update.
>>> >>
>>> >>
>>> >> >
>>> >> > One further possible quirk noticed just before getting home, is 
>>> >> > that
>>> it
>>> >> > appeared that vaccuum drops 2 or 3 inches when making a sharpish rh
>>> >> > turn!!!
>>> >> > Further investigation needed I think :lol:  Does orientation[
>>> rotation]
>>> > of
>>> >> > vane pump have any effect upon operation?
>>> >> >
>>> >> > Quantum Bentley $46 delivered to UK. I suppose it is a heavy book.
>>> >> > but
>>> >> > I
>>> >> > thought we were the 52 state of America ;op
>>> >> >
>>> >> > Mark
>>> >> >
>>> >> > ----- Original Message -----
>>> >> > From: "mark shepherd" <mark at shepher.fsnet.co.uk>
>>> >> > To: "vw fans" <Vwdiesel at vwfans.com>
>>> >> > Sent: Wednesday, December 17, 2008 3:50 PM
>>> >> > Subject: Re: [Vwdiesel] Brake boost failure....Update.
>>> >> >
>>> >> >
>>> >> >>
>>> >> >> Vac  holds  for hours. In fact there may be a residue overnight!
>>> > Plenty
>>> >> >> of lubrication in chamber.  This morning ran to town. No vaccuum 
>>> >> >> on
>>> >> >> gauge,
>>> >> >> until driven  a mile or so , and then it returned completely 
>>> >> >> within
>>> >> >> a
>>> > few
>>> >> >> seconds. Operates every trip  immediately, and hot  or cold 
>>> >> >> reaches
>>> > about
>>> >> >> 23 in wg. Problem must be with the vanes somehow.  Temp this
>>> >> >> morning
>>> > was
>>> >> >> around zero. Car windows iced yet no ground frost.
>>> >> >> Maybe there is too much oil?
>>> >> >> More pointers please.
>>> >> >> Mark
>>> >> >>
>>> >> >> Sniped  a Quantum Bentley a few days ago  for $6, alas postage may
>>> >> >> kill
>>> >> >> me
>>> >> >> though!
>>> >> >>
>>> >> >>
>>> >> >> >
>>> >> >>
>>> >> >
>>> >> >
>>> >> > _______________________________________________
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>>> >> > Vwdiesel at vwfans.com
>>> >> > http://www.audifans.com/mailman/listinfo/vwdiesel
>>> >> >
>>> >> >
>>> >>
>>> >>
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>>> >
>>> >
>>> >
>>> >
>>>
>>>
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