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Grady Clay's Avatar
Join Date: Dec 2003
Location: Arapahoe County, Colorado, USA
Posts: 9,032
Defective new Carrera oil pump

Defective new Carrera oil pump.

One of my long term friends has a track only 911 –
a 2.8 ’69 911 that is very well professionally prepared.

Here is the engine:
92x70.4 = 2808 cc, new Mahle Nikasil RSR P&Cs at 11.5:1,
G-80 cams, perfect ’77 case, Motec EFI and twin plug. All
the proper stuff nicely done. Normally run to 7600 RPM,
probably capable of 8200 and more.

Here is the oil system:
New Factory Carrera oil pump 911.107.008.05.
Dash-12 oil lines directly to front cooler with an
in-line screen filter.
No thermostat – just tape off cooler.
No pressure relief in the scavenge circuit - just
careful warm-up from cold.
Front (smugglers box & above) oil tank.
Dash-16 line back to pressure pump inlet with
an in-line screen filter.
Two separate breathers, one at the engine and
one at the sump tank, each with a 1+ liter catch
tank. No breather connection between the
crankcase and the sump tank.

Here are the symptoms:
Increasingly there is oil pumped into the catch
tank at the engine, none at the sump tank.
At first there was none and eventually, after six
hours total, 3-4 at-speed laps caused the crankcase
to become full of oil, including the catch tank, and the
oil sump tank too little. The oil pressure of course
fluctuated and the car parked.

Upon D&D (Disassembly and diagnosis):
Rod bearings showing wear (expected due to the
oil pressure fluctuation).
Everything else was as expected


Here is the Factory new oil pump.

The depth of the missing casting is about 0.20 mm.
It covers about 70° of a total of 120° of the sealing
surface of the scavenge gear pump. Clearly this may
be the problem.

My perception is the scavenge pump couldn’t keep up
with the necessary oil flow. This was exacerbated by
high RPM and increasing oil temperatures.

While I prefer to have the crankcase breather connected
to the sump tank (like Factory) this set-up has worked
well for many.

While there is an apparent cause, I’m not convinced.
I fully expected to see a cracked oil pump from the
lack of thermostat/pressure relief. With our collective knowledge, what else could be a cause? Replacing
the oil pump is easy and no permanent damage was
done. Is there something else here?

My question to the Forum is:
Separately or in combination with
the scavenge pump, is there anything
else that could cause these symptoms?

Old 12-14-2005, 06:46 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
what? me worry?
TimT's Avatar
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 6,944
That wear pattern looks odd. Wouldnt you expect it to be uniform?

Or its not a wear pattern at all.... A problem with the "Defective new Carrera oil pump" may have been there before you ever installed it

Perhaps the the casting got fubared, the machining couldnt fix it....

who knows we just had a GT3 pump explode.. no pictures for forensics
who are those guys? <<< ( Butch Cassidy and the Sundance Kid)
Rent a GT3RS from us!! Call or e-mail.
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Old 12-14-2005, 07:15 PM
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HawgRyder's Avatar
Join Date: Feb 2002
Location: Langley, BC Canada
Posts: 2,865
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Looks like there was a void in the casting and after machining the chamber it was not properly inspected.
I would take it back and ask for a new pump and compensation for rebuilding the engine.
When you get the new pump, check the inside before installing.
Porsche may have a problem with this series of pumps (production run) and I'm sure they would like to find out.
Bob Hutson
Old 12-15-2005, 06:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)

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