Cont O-300D oil leak problem

Well, I guess tightening up the through-bolts is OK, as long as you
don't over-torque them.

I just rebuilt an O-300 and have worked on several of them. They are
great engines, though at 145HP and 7 to 1 compression not behemoths of
power. Crush washers on the rear case and on the oil sump are bad to
leak, if they have been over-used. Buy new ones; they're cheap anyhow.
Sometimes you'll have a leak on the rear case where a stud has been
pulled loose from the magnesium housing, like at the seal cover for the
tach drive.

I see a lot of leaks around the pushrod-tube-to-crankcase boots, which
are easy to get off their seats or not have their spring clamps seated
properly. Those boots are tough and will last to TBO, but sometimes
you'll have to adjust one to get it to do its work.

To find a leak I always clean the engine and fire it up with the cowl
off. Run it just long enough to get the oil warm and don't fry your
cylinders. Leave your aircraft on the ramp so you can see where it's
dripping. Invariably we have found our culprit leak and been able to
stop it.

I always paint gaskets like valve cover gaskets, and all the other
gaskets, with High-Tack, front and back. If you get any leak around
any of those gaskets the oil will be dyed red by the High-Tack, so you
know generally where it's coming from.

Of course, CA glue is great for stopping seepage around bolts and seams
in the case. Put a vacuum cleaner to the oil filler and apply the
glue.

Finally, if people would handle cylinders gingerly and not hold them by
their pushrod tubes, the damn things wouldn't leak. Having to use
that beading tool to seal the tubes inside the cylinder head just means
the cylinder was abused by someone.

Originally Posted by

Of course, CA glue is great for stopping seepage around bolts and seams
in the case. Put a vacuum cleaner to the oil filler and apply the
glue.

----------------------

maybe everyone besides me knows this, but what is "CA glue" - CyanoAcrylate glue?

TIA,

frank

clipclip wrote:

maybe everyone besides me knows this, but what is "CA glue" -
CyanoAcrylate glue?

Contact Adhesive aka Superglue

Finally, if people would handle cylinders gingerly and not hold them by
their pushrod tubes, the damn things wouldn't leak. Having to use
that beading tool to seal the tubes inside the cylinder head just means
the cylinder was abused by someone.

Amen to that. However, the aluminum head expands at twice the rate of
the steel tubes (the coefficient of linear thermal expansion) and this
tends to leave the tubes a little loose when things are hot. I don't
know if Continental relied on the metal-to-metal seal when they
manufactured them, or if there was some sort of sealant used that
crumbles or disappears with age. That's why I use the Loctite, after
the cylinders are installed so that the tubes won't be moved anymore,
and the Loctite, being plastic and having a much larger expansion rate
than even aluminum, keeps things sealed up all the time. Loctites reach
their maximum strength at around 300 degrees, too.

Dan

My mechanics have replaced all 6 rocker box
covers and gaskets, and re-flared the push rod tubes. I have spent
almost $1000.00 so far and it's still leaking.

You told your mechanic that you had an oil leak, and that he should go fix
it?

Whoo-eee...I'll bet he's had visions of sugar plums dancing in his head for
weeks! Talk about a license to steal...

Never, ever send an A&P on a fishing expedition. You'll only get hooked,
and everything will smell fishy...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

My mechanics have replaced all 6 rocker box
covers and gaskets, and re-flared the push rod tubes. I have spent
almost $1000.00 so far and it's still leaking.


JayYou told your mechanic that you had an oil leak, and that he
should go fix
it?
Whoo-eee...I'll bet he's had visions of sugar plums dancing in his head
for
weeks! Talk about a license to steal...

Not at all. I was there every minute, observing everything. I even
flew to Danbury (Coastal Aviation) to pick up the new rocker box covers
myself. I did the runups on the ramp after each attempt to fix it.
These guys were definitely not trying to exploit me, and they are just
as frustrated as me by the persistant leak. In fact, I am forwarding
all the comments from the NG to them at their request. They want to
fix it as much as I do.

Never, ever send an A&P on a fishing expedition. You'll only get
hooked,
and everything will smell fishy...

Sound advice, but this is not the case here. Thanks . . .


www.Rosspilot.com

Never, ever send an A&P on a fishing expedition. You'll only get
hooked,
and everything will smell fishy...

Sound advice, but this is not the case here. Thanks . . .

I know you didn't, Lee. I guess I forgot the little smiley thingy...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Small Continentals typically leak from both ends of the pushrod
tubes. The rubber couplings at the case need to be replaced, which
requires pulling the cylinders off, at which time the cylinder base
seals (o-rings) should be done, too. The head end of the tubes will
often leak until the rocker covers are removed, cleaning solvent (like
Brake and Parts Cleaner or laquer thinner) is used to flush out the
tube/head joints, and a wicking Loctite is run into them. If it's the
front crankshaft seal, there's a split version available to install
without any fuss.
The oil tank or accessory cover gaskets might be leaking, and
worst of all, the crankcase joint might be starting to seep.

Dan

If the pushrod tubes are the same as on the big bore Continentals then
the cylinders do not need to be pulled, you just need the tool to
compress the springs. And no mechanic worth the title uses loctite on
those tubes. If you get the gaskets in right they do not leak. Very
easy to tell with a little mirror.



wrote:

Small Continentals typically leak from both ends of the pushrod
tubes. The rubber couplings at the case need to be replaced, which
requires pulling the cylinders off, at which time the cylinder base
seals (o-rings) should be done, too. The head end of the tubes will
often leak until the rocker covers are removed, cleaning solvent (like
Brake and Parts Cleaner or laquer thinner) is used to flush out the
tube/head joints, and a wicking Loctite is run into them. If it's the
front crankshaft seal, there's a split version available to install
without any fuss.
The oil tank or accessory cover gaskets might be leaking, and
worst of all, the crankcase joint might be starting to seep.

Dan

wrote:
My mechanics have replaced all 6 rocker box
covers and gaskets, and re-flared the push rod tubes. I have spent
almost $1000.00 so far and it's still leaking.



JayYou told your mechanic that you had an oil leak, and that he
should go fix
it?
Whoo-eee...I'll bet he's had visions of sugar plums dancing in his head
for
weeks! Talk about a license to steal...

Not at all. I was there every minute, observing everything. I even
flew to Danbury (Coastal Aviation) to pick up the new rocker box covers
myself. I did the runups on the ramp after each attempt to fix it.
These guys were definitely not trying to exploit me, and they are just
as frustrated as me by the persistant leak. In fact, I am forwarding
all the comments from the NG to them at their request. They want to
fix it as much as I do.

Well clearly there was more work done than new gaskets and some flaring.
The new gaskets are about $8 each if you get the good silicone ones.
Takes an hour to install them, at most.