Oil Coolers

Not necessarily, the oil pressure gauge lines are very small
to prevent a major leak if the line breaks, in cold weather
or just with cold oil, the gauge will respond slower. That
is one of the reasons they say to allow 30 seconds for oil
pressure to show up after a start, it takes some time.

But a stuck relief valve will cause the oil pressure to go
very high instantly and that blows the seals or oil cooler
which drops the pressure before the gauge has time to
respond.


"Neil Gould" wrote in message
. net...
| Recently, Jim Macklin
posted:
|
| If it happens it will be fast, faster than the gauge
will
| likely respond. The oil pump is a set of meshed gears
that
| move the oil. They move a fixed amount with each
revolution
| of the engine. There is a spring loaded pressure relief
| valve in the pump that by-passed oil back to the pump
intake
| if the pressure is high.
| Chapter 6 of AC 65-12
|
|
http://www.airweb.faa.gov/Regulatory...0?OpenDocument
| has diagrams and explanations.
|
| Thanks, I'll look it over.
|
| During an overhaul of an engine, a valve can become
jammed,
| blocked or otherwise adversely effected. The valves
should
| be clean and function checked. But a metal chip or
other
| problem can happen and can get into a pump system.
Often
| the relief valves are stuck open and you don't get full
| pressure, but it can stick a valve closed and then the
| pressure goes up until something breaks or a seal blows.
|
| If the valve sticks closed, wouldn't the oil pressure
gauge be "pinned"
| high?
|
| Neil
|
|
|

unicate wrote:
In October, after an extensive repair/restoration of my airplane, the
oil cooler split on start-up and dumped most of the oil. Long story, but
the engine seized up 6 minutes into the flight and we did an emergency
landing in the desert. We were very fortunate to walk away with minor
injuries, but the plane was totaled.

To the airplane owners out there, how often do you flush/pressure test
or replace your oil cooler? Some say it's only done at a major overhaul,
others say it should be done at every annual, others say only if there's
a problem w/oil pressure. I had never heard of an oil cooler failing
before this, but now I've heard people say it happens on occasion.

After replacing the oil cooler you should have done at least a 10
minute ground run with someone outside watching for oil leaks. Same
procedure as for an oil change.

-RObert

Jim Burns wrote:
In addition to JimM's great information, check out
http://www.oilcoolers.com/ , Pacific Oil Cooler Service. Lots of good info
there. If you get to OSH next summer, look them up. You'll be amazed at
how much crud can accumulate in your oil cooler.

I had these guys O/H my Mooneys oil cooler and haven't had any
problems.

-Robert

"Robert M. Gary" wrote:

To the airplane owners out there, how often do you flush/pressure test
or replace your oil cooler? Some say it's only done at a major overhaul,
others say it should be done at every annual, others say only if there's
a problem w/oil pressure. I had never heard of an oil cooler failing
before this, but now I've heard people say it happens on occasion.

After replacing the oil cooler you should have done at least a 10
minute ground run with someone outside watching for oil leaks. Same
procedure as for an oil change.

We did not replace the oil cooler, it was not disturbed throughout the
entire repair, which is part of the reason for my question. *Of course*
we did ground-run tests after the engine repair, and at 8 hours after
the repair when we replace the mineral oil with Aeroshell 100. No leaks
were present, either time. My question was, SHOULD the oil cooler have
been flushed/pressure tested since a major repair had been done, and/or
how often do mechanics generally recommend that this be done?

Shirl

"Jim Macklin" wrote:
Not necessarily, the oil pressure gauge lines are very small
to prevent a major leak if the line breaks, in cold weather
or just with cold oil, the gauge will respond slower. That
is one of the reasons they say to allow 30 seconds for oil
pressure to show up after a start, it takes some time.

But a stuck relief valve will cause the oil pressure to go
very high instantly and that blows the seals or oil cooler
which drops the pressure before the gauge has time to
respond.

My gauge didn't respond until 5-6 minutes into the flight, but the
cooler obviously split on start-up, as there was a huge puddle there and
another in the run-up area (and no, I had never been taught to look
behind when I pull away to assure there are no puddles, though I sure do
NOW! ... how many pilots that have not had an incident/accident like
this routinely do this?). The oil pressure gauge remained in the normal
position throughout start-up, run-up, takeoff, climb-out and during the
first couple of minutes of cruise; then it read zero pressure.

If you had a constant speed prop, it would have failed to a
high rpm and you would have probably had to reduce power to
stay under redline.

This might have happened before the gauge showed no oil
pressure.



wrote in message
...
| "Jim Macklin"
wrote:
| Not necessarily, the oil pressure gauge lines are very
small
| to prevent a major leak if the line breaks, in cold
weather
| or just with cold oil, the gauge will respond slower.
That
| is one of the reasons they say to allow 30 seconds for
oil
| pressure to show up after a start, it takes some time.
|
| But a stuck relief valve will cause the oil pressure to
go
| very high instantly and that blows the seals or oil
cooler
| which drops the pressure before the gauge has time to
| respond.
|
| My gauge didn't respond until 5-6 minutes into the flight,
but the
| cooler obviously split on start-up, as there was a huge
puddle there and
| another in the run-up area (and no, I had never been
taught to look
| behind when I pull away to assure there are no puddles,
though I sure do
| NOW! ... how many pilots that have not had an
incident/accident like
| this routinely do this?). The oil pressure gauge remained
in the normal
| position throughout start-up, run-up, takeoff, climb-out
and during the
| first couple of minutes of cruise; then it read zero
pressure.

I'd have to look at the spec, but an oil cooler is probably
pressure tested / designed to hold at 400-500 PSI. Since
the oil pressure is regulated at 35-90 PSI there is a good
margin for minor oil pressure spikes. But the oil pump can
far exceed that if the relief valve is stuck, it can produce
oil pressures as high as a good hydraulic pump, just not the
volume.

Nice to have a report on a company.



"Robert M. Gary" wrote in message
ups.com...
|
| Jim Burns wrote:
| In addition to JimM's great information, check out
| http://www.oilcoolers.com/ , Pacific Oil Cooler Service.
Lots of good info
| there. If you get to OSH next summer, look them up.
You'll be amazed at
| how much crud can accumulate in your oil cooler.
|
| I had these guys O/H my Mooneys oil cooler and haven't had
any
| problems.
|
| -Robert
|

unicate wrote:
"Robert M. Gary" wrote:
We did not replace the oil cooler, it was not disturbed throughout the
entire repair, which is part of the reason for my question. *Of course*
we did ground-run tests after the engine repair, and at 8 hours after
the repair when we replace the mineral oil with Aeroshell 100. No leaks
were present, either time. My question was, SHOULD the oil cooler have
been flushed/pressure tested since a major repair had been done, and/or
how often do mechanics generally recommend that this be done?

When Pacific Oil Coolers returned my after cleaning it out they
included a description of the flush and pressure test they did.

Jim Macklin wrote:
I'd have to look at the spec, but an oil cooler is probably
pressure tested / designed to hold at 400-500 PSI. Since
the oil pressure is regulated at 35-90 PSI there is a good
margin for minor oil pressure spikes. But the oil pump can
far exceed that if the relief valve is stuck, it can produce
oil pressures as high as a good hydraulic pump, just not the
volume.

Many engines have the oil pressure relief valve at the far end of the
lubrication system so that pressure is maintained to all parts even
when oil is cold and reluctant to flow. Other systems have a relief
valve in the pump itself, like an automobile's, which might open and
dump the pressure if the oil is too thick, reducing flow to other
components down the line but saving the cooler.
Many systems have a temperature valve that bypasses the oil cooler
until the oil warms up. The pressure is still there against the cooler
because it's plumbed into the system, but the pressure on the two lines
is equal and oil doesn't flow until the bypass closes. With the cold
oil being reluctant to flow into the system from the pump, and the
relief valve way down at the end of the line waiting for pressure, the
oil cooler can get a pressure spike that swells the channels in it. The
expanded metal can sometimes be seen if the cooler is off and a light
shone through the fins. Enough swelling and they split.

Dan

wrote in message
...
In October, after an extensive repair/restoration of my airplane, the
oil cooler split on start-up and dumped most of the oil. Long story, but
the engine seized up 6 minutes into the flight and we did an emergency
landing in the desert. We were very fortunate to walk away with minor
injuries, but the plane was totaled.

To the airplane owners out there, how often do you flush/pressure test
or replace your oil cooler? Some say it's only done at a major overhaul,
others say it should be done at every annual, others say only if there's
a problem w/oil pressure. I had never heard of an oil cooler failing
before this, but now I've heard people say it happens on occasion.

Anyone else here have experience with this?

Shirl

A friend had one split in a 2 year old Mooney 201 over Eastern Oregon
desert. We went to Boise to pick up an Aztec, and decided to fly "together"
on the way home. (Medford,Or) 20 Minutes out of Boise, I had been flying
his right wing, and gradually slipped under/behind to the left side. He had
a 2 foot side black stripe from the cowling to the tail. We turned a bit to
the right to divert to Baker, and he had normal pressure and slightly rising
temps as we landed. I think he still had almost 2 qts left in the 700 hr tt
engine. I always wondered what would have happened if we hadn't stuck
together that day.

Al G