Paul,
You got away lightly with that repair.
Crankcase fretting was a problem common to a small batch of 912 engine
numbers, to the extent that Rotax would offer a replacement casing,
which otherwise costs GBP3,000 (or USD4,500 at Lockwood)
I understand that the fretting occurs mostly around the centre main
bearing support. The same thing happens in VW cases.
Duncan McF.
----- Original Message -----
From: Paul McAllister
To: europa-list@matronics.com
Sent: Friday, April 03, 2009 11:56 PM
Subject: Europa-List: Engine oil leak update
Hi all,
I just wanted to give you an update on my Rotax leaking crankcase.
About a year ago I saw a small oil leak start on the engine just behind
the gearbox on the flat machined surface on top of the engine. After a
while the leaking area started to slowly progress along the case towards
the back of the engine and then along the bottom. While I was at the
Oshkosh airshow I went and talked to the mechanic from Kodiak to get his
opinion. He told me that some 912 / 914's were getting crankcase
fretting and over time the cases were damaged to such an extend that
they had to be replaced. His advice to to have the engine stripped and
inspected.
Well this winter I removed the engine and took it to Leading Edge
Airfoil who has a rotax trained A&P on staff. He stripped the engine
and sure enough it was showing signs of fretting. The engine has about
750 hours on it at the moment. Fortunately it was not too bad and he
was able to dress the cases and re assemble the engine. He used a
different sealant, 5150 I believe it was called instead of the red
Locktite sealant that was on before. He tells me that Rotax now specify
this sealant. It is a heavier material and apparently is swells a
little after application, perhaps from heat, I am not sure. He felt
confident that this would tighten things up and I should not have any
problems. A couple of other things to note, at 750 hours there was no
sign of wear in any part of the engine. The only thing he mentioned was
a slight scuff on a cam follower that would have been from not priming
the engine properly after an oil change. I remember exactly when I did
that ! He as able to polish it out. There was a little bit of oil
flashing on some of the piston skirts and he told me that this was from
using either mineral or semi synthetic. I have been using the
recommended Penzol motorcycle oil although this has dropped off the list
in recent times, so I changed to the Valvoline Durablend. He was
strongly recommending I go to a full synthetic oil. He also wanted me to
stop using the Challenger oil filters, he tells me that they have less
pleats in them. The only other thing of note was the Turbo charger
bracket was broken.
So it would appear that Kodiak was right and if I hadn't had this work
done I would have lost the cases. While he had it apart he overhauled
the gearbox which was due, replaced the plugs, and the rubber boots on
the carburettors, so my oil leak repair came to 3900 dollars. Ouch.
Rotax really have no shame, the gasket set is over a 1000 dollars for
something that has a trivial manufactured cost but there is little that
any of us can do about that matter.
The aircraft is going to be a little while before it is flying again,
I have decided to take a crack at some cooling modifications while it is
all apart.
Paul
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