[V8] Emergency pentosin decisions

dsaad at icehouse.net dsaad at icehouse.net
Mon Oct 18 11:31:21 EDT 2004

I am not trying to second guess Earl here - but I can not see how a bad bomb
could overload the pump. If the bomb fails to "accumulate" pressure, the pump
would never know. It will still always supply oil at max pressure and flow. The
only difference is that you will not have any reserve pressure for rapid pedal
Your pump seems to have failed - no doubt about that but maybe it failed for its
own selfish reasons. The bomb is just a scapegoat.

I installed a filter in the rack return line of my system on the recomendation
of a local Audi nut. My rack is dry as a bone at 140K.
My pump sprang a leak from the front seal a while back, but it was rebuilt and
has been dry ever since.
The gut who rebuilt my pump said that it was quite common to have a cascade of
problems after the first failure because of contamination in the system.
I think one common failure mode of this system is lack of hydraulic oil service.
It should probably be changed much more often than Audi recomends because as the
oil ages it gets a sort of rubber like formation in it. This gunk is what takes
out the seals. It was for this reason the filter seemed like a good idea - and
it is cheap and easy to do - around $25 for the filter + a few dollars for
hydraulic hose and screw clamps.

The oil I took out (when the front seal failed) was likely OEM - and it was
black and gritty. The oil I replaced it with was a Pentosin replacement, and it
is clear when new. It is cloudy now - but there is no sludgy gunk in the
strainer screen (after about two years now) like there was before. I am pretty
convinced that the filter is going to save me a lot of money over time.

If interested, I used a generic inline automatic transmission filter designed to
be installed in the cooler lines. The filter can handle the oil temperatures and
pressures expected in an automatic transmission - which is much more severe than
the hydraulic system return line will ever see. It also has a bypass valve and
magnetic pickup internally. I cut (carefully!) the return line rubber hose off
the hard line near the oil tank and ran new hydraulic hose over near the A/C
evaporator where I located the filter, and back again to the tank. The filter is
easy to service and out of the way here.


Quoting Ralph Cook <blusgtar at ptd.net>:

> I spoke to My Audi Tech today, (Earl Huber and I have a close relationship,
> he runs barefoot through my wallet twice a year).
> The loss of hydraulic fluid was caused by a major leak in the pump itself.
> It was suggested that the bomb was failing and caused the pump to overload.
> So it means a new pump and bomb for me. That results in about $4,000 this
> year for repairs to my 93 V8Q.
> I am thinking that it should be sold before Christmas, I cannot afford to
> keep a car that cannot be trusted to stay together on a long trip.
> Ralph L. Cook
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