Oil leak on top of the engine

It seems to be the season for finding oil leaks.

At our completely uneventful annual (just finished two days ago) I asked my
shop to investigate a new leak that I had detected when I de-cowled the
engine for the inspection. All across the top of our 3-year-old, 500-hour
engine, down the seam where the case halves join together, right where the
push rods attach to the case, was a puddle of fresh, clean oil -- enough to
look like I had just spilled some while adding oil...

Trouble was, I HADN'T added any oil recently. With our new air/oil
separator, I no longer need to add oil between oil changes, so it had been
some 24 flight hours since I had last added oil.

With no obvious source of the leak, my mechanic thoroughly cleaned the
engine and resolved to fly it to see where the oil was coming from. The
flying weather wouldn't cooperate until today, but this morning we flew the
plane on its post-annual test flight, found a squawk or two, and returned to
the shop to fix these and check for the source of the leak.

The total flight time was only 0.7 hours, yet the top of the engine once
again looked like I had spilled oil while filling. It was right along the
case halves seam, so with no other apparent source my mechanic figured the
first place to start was to check the torque on the case bolts.

He reached for the first one, and we were both astounded when he was able to
tighten it -- by hand! One by one, all of the case nuts were found to be
very loose (although that was the only one that was hand-tight), and needed
to be re-torqued to 190 inch pounds of torque.

After tightening those, he checked the prop governor housing, and found
those bolts to be way loose, too. Essentially the whole top of the engine
was loose, and oil was leaking at the seam.

After re-torquing everything to spec, I test flew the plane for another 0.5
hours, and was happy to see everything bone dry once again.

Questions:

1. Is this something one should expect after 500 hours of shaking and
rattling? Do these bolts just plain loosen over time, going from hot to
cold hundreds of times?

2. Do you guys re-torque these bolts on a schedule?

3. Is this something your A&P checks at every annual? My guys were clearly
surprised to find these bolts so loose -- and they are the guys who rebuilt
the engine.

4. Are there any other bolts -- say, on the BOTTOM of the engine -- that I
should check for looseness? I looked but couldn't see any.

5. Should I apply LocTite to these bolts?

I suspect I'll be checking those bolts regularly from now on!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

No they shouldn't be that loose. Torqueing a bolt is to put a higher load
on it then the load it sees in service.
It wasn't torqued to begin with or something else has changed..

I would check all the cylinder holdown nuts and thru-bolts before I flew it
again.

Lyc or TCm has a service bltn explaining how to measure the rotating
resistance of the engine by using a spring scale on the prop. Take a
measurement then torque the thru bolts then take another measurement.
A significant change is signs of bearing pinch.

Good luck and hope for the best.

Kent Felkins

"Fly" wrote in message
...
No they shouldn't be that loose. Torqueing a bolt is to put a higher
load
on it then the load it sees in service.
It wasn't torqued to begin with or something else has changed..

I would check all the cylinder holdown nuts and thru-bolts before I flew
it
again.

Lyc or TCm has a service bltn explaining how to measure the rotating
resistance of the engine by using a spring scale on the prop. Take a
measurement then torque the thru bolts then take another measurement.
A significant change is signs of bearing pinch.

Good luck and hope for the best.

Kent Felkins



This one gets my vote for thread of the week, I will watch out for this from
now on. I am suprised its not on the annual check list. In fact, I may have
to go check for that.

A significant change is signs of bearing pinch.

What's "bearing pinch"?

Dunno if this matters, but all compressions are in the high 70s, oil
consumption is better than average, and it runs great.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

DAMN!

No, that's absolutely not normal. Poor workmanship at the rebuilder.

There are bolts that should have been retorqued at a certain hour.
The shop would have specified which ones.

I really don't know of anyone who makes it a habit to check the torque
on all the engine bolts at each annual. Things like exhaust studs
hardware and intake bolts are checked.

Understand this. If the case is fretting, as it does when bolts are
loose, it's a very serious situation. If this were my engine, I would
have another mechanic check the torque of the through bolts. If
they're off you need to clean it up very well and run it for about
another 1/2 hour on the ground. Do Not Fly This Airplane. If wet,
the engine needs to be pulled and the disassembled, cases sent out and
reassembled. It'll give you something to talk about, anyway.

Don't take my word for it, contact a real engine house for advice and
let the world know if I'm wrong.

I seem to remember being strongly criticized after saying something
about soliciting recommendations for a shop via the newsgroups when
you did it a few years back.


On Thu, 10 Feb 2005 21:25:10 GMT, "Jay Honeck"
wrote:

It seems to be the season for finding oil leaks.

At our completely uneventful annual (just finished two days ago) I asked my
shop to investigate a new leak that I had detected when I de-cowled the
engine for the inspection. All across the top of our 3-year-old, 500-hour
engine, down the seam where the case halves join together, right where the
push rods attach to the case, was a puddle of fresh, clean oil -- enough to
look like I had just spilled some while adding oil...

Trouble was, I HADN'T added any oil recently. With our new air/oil
separator, I no longer need to add oil between oil changes, so it had been
some 24 flight hours since I had last added oil.

With no obvious source of the leak, my mechanic thoroughly cleaned the
engine and resolved to fly it to see where the oil was coming from. The
flying weather wouldn't cooperate until today, but this morning we flew the
plane on its post-annual test flight, found a squawk or two, and returned to
the shop to fix these and check for the source of the leak.

The total flight time was only 0.7 hours, yet the top of the engine once
again looked like I had spilled oil while filling. It was right along the
case halves seam, so with no other apparent source my mechanic figured the
first place to start was to check the torque on the case bolts.

He reached for the first one, and we were both astounded when he was able to
tighten it -- by hand! One by one, all of the case nuts were found to be
very loose (although that was the only one that was hand-tight), and needed
to be re-torqued to 190 inch pounds of torque.

After tightening those, he checked the prop governor housing, and found
those bolts to be way loose, too. Essentially the whole top of the engine
was loose, and oil was leaking at the seam.

After re-torquing everything to spec, I test flew the plane for another 0.5
hours, and was happy to see everything bone dry once again.

Questions:

1. Is this something one should expect after 500 hours of shaking and
rattling? Do these bolts just plain loosen over time, going from hot to
cold hundreds of times?

2. Do you guys re-torque these bolts on a schedule?

3. Is this something your A&P checks at every annual? My guys were clearly
surprised to find these bolts so loose -- and they are the guys who rebuilt
the engine.

4. Are there any other bolts -- say, on the BOTTOM of the engine -- that I
should check for looseness? I looked but couldn't see any.

5. Should I apply LocTite to these bolts?

I suspect I'll be checking those bolts regularly from now on!

On 2/10/2005 15:12, Jay Honeck wrote:

A significant change is signs of bearing pinch.

What's "bearing pinch"?

Dunno if this matters, but all compressions are in the high 70s, oil
consumption is better than average, and it runs great.

From my automotive days, this is where the bearings are either
not seated properly, or are not the proper size to fit, and
torquing down the case bolts results in compressing the bearings
onto the crank, resulting in restricted movement and generally
a chewing up of the bearings and/or crank.


--
Mark Hansen, PP-ASEL
Sacramento, CA

"Jon A." wrote:

I really don't know of anyone who makes it a habit to check the torque
on all the engine bolts at each annual. Things like exhaust studs
hardware and intake bolts are checked.

The case bolts on my previous Continental IO-520, circa 1987, had white
paint stripes painted on them to indicate whether they had come loose. The
previous owner, a one-time automotive racer, had a colorful name for these
stripes but at the moment I cannot recall it.

--
Peter













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On Thu, 10 Feb 2005 18:51:03 -0500, "Peter R."
wrote:

"Jon A." wrote:

I really don't know of anyone who makes it a habit to check the torque
on all the engine bolts at each annual. Things like exhaust studs
hardware and intake bolts are checked.

The case bolts on my previous Continental IO-520, circa 1987, had white
paint stripes painted on them to indicate whether they had come loose. The
previous owner, a one-time automotive racer, had a colorful name for these
stripes but at the moment I cannot recall it.

You can use a product called "Torque Seal", available from Spruce for
this. All of your fuel connections should be done. Doesn't actually
seal the torque, but shows you if something has moved.

"Jon A." wrote:

You can use a product called "Torque Seal", available from Spruce for
this. All of your fuel connections should be done. Doesn't actually
seal the torque, but shows you if something has moved.

I think I now recall the name the previous owner called those paint
stripes. "Sabotage spotter."

--
Peter













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What's "bearing pinch"?



Severe case of the crankcase halves rubbing against each other and over time
grinding away.
Thus the bore for that crank bearing is smaller. It keeps working ok for
a while because its a loosed fit. But if you retorque the thru bolts you'll
squeeze the bore back tighter and its smaller diameter will pinch the
bearing halves together, and maybe cause direct metal to metal contact
between the crank and bearing.

Many engines have dowel pins that fit the halves together to minimize
fretting.

Btw, I don't have the torque value bulletin handy but it seems tha the case
spine bolts are only torqued down to 7-10 ft lbs. Not that much but
definitely more than finger tight!

Kent Felkins