Oil leak on 2.5L engine (and the fix)

23 Oct 2005 Oil leak on 2.5L engine (and the fix)

Update 20210918: I didn’t install the Eggenfellner Subaru engine, so any post that references that can be ignored or used as a cautionary tale about how to avoid wasting many years and $50k.

I changed the oil in my engine and PSRU recently. Afterwards I
started the engine and ran it for about 15 minutes with the cowl off
and then checked all around for leaks. To my dismay, I found the
bottom of the oil filter had oil on the bottom of it.

After reading the
Subaru Engine manual section on oil filter changes, I first thought I
had overtightened the filter…the manual says that overtightening
the filter will cause a leak. So I replaced the filter with a new
one and was careful to only go 3/4 turn passed the first “touch
point”. I restarted the engine and did another test. Unfortunately,
the leak still existed. Further investigation revealed the leak to
be coming from the top of the 1″ or so thick aluminum ring that the
filter screws on to.

I became pretty concerned and
called Robert. He told me that the hex nut that holds the aluminum
ring onto the engine probably came loose. This hex nut can be easily
seen and accessed when you remove the oil filter. It goes onto the
same threaded pipe that the oil filter screws onto. So I removed the
oil filter again and borrowed a 1 1/8″ socket and checked this nut
for looseness. This indeed turned out to be the problem as the nut
was less than finger tight. It took about 2 to 3 turns to cinch it
back up. This cured the problem.

Robert said he thinks this same thing happened to him a while
back…with his older 2.5L engine. That makes two of us. Therefore,
just be aware of this problem and you might want to check the
tightness of this hex nut during oil filter changes. I could have
caused my own problem by screwing in the oil filter too tightly and
jamming it against that hex nut. Then when I loosened/removed the
oil filter I could have unscrewed/loosened the hex nut at the same
time.

I was still a bit concerned about the oil filter coming loose in
flight so I went down to Home Depot and purchased a 3″ aluminum pipe
joint for about $3.50. This photo shows how this pipe joint sleeve fits
over the Fram Filter I installed. I secured it with safety wire to
an adell clamp on the supercharger mounting bracket.

PSRU OIL CHANGE:
Another thing that concerned me was tiny metallic particulates and
flakes noted in the drained PSRU oil. I drained the used PSRU oil in
a clear plastic container and let it set for a while. These
specks/flakes drifted to the bottom. I then used a magnet to
determine if they were aluminum or steel (from the gears). They
moved with the magnetic…therefore came from the gears. However,
there was not in my opinion a significant composite amount of this
loosened material. It is my underestanding that tiny particles and a
few small flakes is pretty common and should not be of much concern.
[If anyone believes contrary, let me know]. (Note that there is no
filter in the psru gear box to collect these particulates). Anyway,
when you drain/change your PSRU oil (I believe every 100 hrs or so is
right), you might want to examine the amount of particulates in the
drained oil. Always check the clarity of the oil in the sight tube.
I was amazed that the drained oil looked so black compared to the oil
in the sight tube.

Pete Krok
Redlands, CA
7A/2.5 s/c

keywords: oil filter, maintenance