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Re: vaccum pump noise [LONG]

Got a couple of requests so I'm posting the whole story.

At least on mine, the removal was simple.  Take off the hose, remove 2 nuts
and it's off.  Be careful, there's a large spring inside the pump and the
pump will want to "jump" off into your hand.  The spring is retained, so
not to worry.

Just turning the pump upside-down, oil runs out....a good deal actually.
Took some work to take off the 6 cover screws...chewed up 2, so I bought
socket-head cap screws to replace all of them...5mm X 12mm-16mm and

Be careful opening the pump...there is an o-ring style gasket in there
which will have stuck to either the pump, the cover, or both and tearing it
would be a BAD idea.  Keep track of any valves that are in there.  There
are many little check valves about as big around as a quarter...they're
loose and will fall out if you turn the pump over.

Took out the check valves and wiped them out and checked for proper
operation.  Used a bench-top bottle capper as an arbor press to actuate the
pump and feel for binding or noise.  More draining takes place here too.

After fiddling with it for a while, I gave it one last good clean and
inspect and reassembled it.  The "rod" I talked about appears to be some
kind of high-carbon steel push rod that remains in the engine
block...almost looks like graphite!  You can reach in and pull it out with
2 fingers.  Remember how it went in!!!  Appears to be a flat machined over
the length of the rod, probably for oil circulation.

Put the pump back on the car and *silence*.  I tried to record the noise
before doing it, but every time it saw the tape recorder coming, it would
shut up.  Then, in a parking lot in the middle of nowhere...it would make
noise...go figure.

It makes a faint tapping every now and then, but NOTHING like it was.  Of
course, it's only been 3 days since, so I don't have many hours of test
time.  3 days of silence is a lot better than before, however.

My theory is that it fills with oil, and hydrostatically binds or restricts
the free movement of the pump shaft.  As the cam rotates around the back
side, the pump frees, the monster spring pushes the shaft out against the
cam and "clack clack clack".  Or, it could be that the rod has worn short
and does not stay in contact with the cam at all times.  A solution would
be to slightly loosen the nut on the end of the pump shaft (the shaft that
has the big spring on it).  This would in effect "lengthen" the shaft to
accomodate for the shortened rod.  However, I hesitate doing this without
knowing more about what the pump is and what it's clearances are.  Might
just be safer to replace the rod.  If someone *does* have the part number,
please post.

Perhaps a "proper" fix would be to completely clean the check valves, as
they were oil covered and may be more stubborn to open and close due to
surface tension of the oil between the flat surfaces of the valves.


 +---------------------| _   /| |---------------------+ Opinions expressed
 |   Chris Ice, CMfgT  | \`o_O' | Allen-Bradley Co.   | are mine and don't
 |   CMIce@mke.AB.com  |   ( )  | 1201 S. Second St.  | reflect views of my
 |   (414) 382-2136    |    U   | Milwaukee, WI 53204 | employer.  So there!
 +---------------------|  Ack!  |---------------------+
  Amiga 2000/030@33MHz  --------  1988 Audi 90 Quattro