Cherokee 140 Oil Temp Creeping Up

Mike Spera wrote:
I have owned this Cherokee 140 since 1994. I have logged over 1000 hours
in it through the original and the now installed overhauled engine. Oil
temps were usually at 180 degrees (both engines)when OATs were between
50-80 degrees or so. It would read 1 needle mark higher when it got to
be 95+ outside. In the last 150 hours or so, it has been drifting up and
is now reading about 2 needle marks above 180 degrees (200 degrees or
so?). I replaced the oil cooler because of age. It was cheaper to
replace it with a new PMA'd unit than to have it checked/cleaned. I
swapped the Vernatherm. No difference. Do the gauges/senders drift off
with age. I am going to test the sender/gauge with hot water and a
thermometer.

Once it gets to that mark, it seems to stabilize.

Baffles are all in good shape.

What else causes temps to drift high? I know that shifting main bearings
can cause this, but I doubt the engine would continue to operate for
this long if this were the case. I do wonder though because the cold oil
pressure is right at redline on takeoff. After 5 minutes it goes back
down into the middle of the green.

Thoughts/theories?

Thanks,
Mike

My oil temp always read low and I took the aircraft temp gage probe and
a multimeter that I had that had a temp probe and heated a small tin can
of oil to 180F, put both probes in the oil, and then marked the aircraft
gage so I would know exactly where 180F was. The O-360 oil was reading
lower than 180 always.

--

Regards, Ross
C-172F 180HP
Sold
KSWI

In article ,
Ross wrote:

Mike Spera wrote:
I have owned this Cherokee 140 since 1994. I have logged over 1000 hours
in it through the original and the now installed overhauled engine. Oil
temps were usually at 180 degrees (both engines)when OATs were between
50-80 degrees or so. It would read 1 needle mark higher when it got to
be 95+ outside. In the last 150 hours or so, it has been drifting up and
is now reading about 2 needle marks above 180 degrees (200 degrees or
so?). I replaced the oil cooler because of age. It was cheaper to
replace it with a new PMA'd unit than to have it checked/cleaned. I
swapped the Vernatherm. No difference. Do the gauges/senders drift off
with age. I am going to test the sender/gauge with hot water and a
thermometer.

Once it gets to that mark, it seems to stabilize.

Baffles are all in good shape.

What else causes temps to drift high? I know that shifting main bearings
can cause this, but I doubt the engine would continue to operate for
this long if this were the case. I do wonder though because the cold oil
pressure is right at redline on takeoff. After 5 minutes it goes back
down into the middle of the green.

Thoughts/theories?

Thanks,
Mike

My oil temp always read low and I took the aircraft temp gage probe and
a multimeter that I had that had a temp probe and heated a small tin can
of oil to 180F, put both probes in the oil, and then marked the aircraft
gage so I would know exactly where 180F was. The O-360 oil was reading
lower than 180 always.

Are the baffle seals in good condition, and curved forward when the cowl
is in place? Also, check the intercylinder baffles, to make sure that
they are properly installed. Any discrepancies in those areas will cause
the cooling air to bypass the cylinders and lead to higher temperatures.

Most production planes have very inefficient cooling, anyhow.

--
Remove _'s from email address to talk to me.

I was seeing oil temps in the red, oil pressure ok but I still landed
immediately. Turns out the wire on the oil temp unit on top of the
engine (don't know what that is) was loose. Correct wrench to remove
the nut, washer and wire. Clean everything. Replace. Tighten correctly
(yes, an A&P was there - next door hangar). No more problem with
oil temps.

The easiest & cheapest fix I've ever had.

On Jun 9, 9:06 am, Blanche wrote:
I was seeing oil temps in the red, oil pressure ok but I still landed
immediately. Turns out the wire on the oil temp unit on top of the
engine (don't know what that is) was loose. Correct wrench to remove
the nut, washer and wire. Clean everything. Replace. Tighten correctly
(yes, an A&P was there - next door hangar). No more problem with
oil temps.

The easiest & cheapest fix I've ever had.

Rising oil temps with electric gauges can sometimes be blamed on
a poor engine grounding strap or alternator ground cable. If there's
resistance between the engine or alternator and the airframe, the
electricity looks for other paths and can find a small one via the oil
temp sensor (which is screwed into the oil filter adapter and is
thereby grounded), through the sensor and up to the gauge, through the
gauge to the bus. The electron flow is in the same direction as the
gauge's normal flwo from the sensor and so any additional flow will
cause a higher gauge reading.
I would suspect a ground connection that is losing its
effectiveness as it heats up. Back of the alternator, ground strap at
the engine or even on the mount, alternator ground at the firewall.
Clean and tighten them. And then run a small wire from some small bolt
on the engine accessory cover near the temp sensor, through the
firewall and to the gauge backplate. That's a Cessna fix for the
issue.

Dan

thread creep

Blanche, your story reminded me of an incident I had a couple years ago. I
flew from Jeffco, Denver (BJC) to Centennial, Denver (APA) to have a
mechanic look at something. I parked in front of his hangar and shut down.
the prop stopped vertical, so, as was my custom at the time, I cleared the
area and blipped the starter to move it. Click. Click. No prop movement. The
starter was fine at Jeffco and inoperative at Centennial. It turned out that
the lug on the high current lead at the starter motor had broken completely
free from the wire. Cheapest fix I've ever had. What are the chances of
discovering the problem while sitting right in front of the mechanic's
hangar!

Jon

/thread creep

"Blanche" wrote in message
...
I was seeing oil temps in the red, oil pressure ok but I still landed
immediately. Turns out the wire on the oil temp unit on top of the
engine (don't know what that is) was loose. Correct wrench to remove
the nut, washer and wire. Clean everything. Replace. Tighten correctly
(yes, an A&P was there - next door hangar). No more problem with
oil temps.

The easiest & cheapest fix I've ever had.

Orval Fairbairn wrote:
In article ,
Ross wrote:

Mike Spera wrote:
I have owned this Cherokee 140 since 1994. I have logged over 1000 hours
in it through the original and the now installed overhauled engine. Oil
temps were usually at 180 degrees (both engines)when OATs were between
50-80 degrees or so. It would read 1 needle mark higher when it got to
be 95+ outside. In the last 150 hours or so, it has been drifting up and
is now reading about 2 needle marks above 180 degrees (200 degrees or
so?). I replaced the oil cooler because of age. It was cheaper to
replace it with a new PMA'd unit than to have it checked/cleaned. I
swapped the Vernatherm. No difference. Do the gauges/senders drift off
with age. I am going to test the sender/gauge with hot water and a
thermometer.

Once it gets to that mark, it seems to stabilize.

Baffles are all in good shape.

What else causes temps to drift high? I know that shifting main bearings
can cause this, but I doubt the engine would continue to operate for
this long if this were the case. I do wonder though because the cold oil
pressure is right at redline on takeoff. After 5 minutes it goes back
down into the middle of the green.

Thoughts/theories?

Thanks,
Mike
My oil temp always read low and I took the aircraft temp gage probe and
a multimeter that I had that had a temp probe and heated a small tin can
of oil to 180F, put both probes in the oil, and then marked the aircraft
gage so I would know exactly where 180F was. The O-360 oil was reading
lower than 180 always.

Are the baffle seals in good condition, and curved forward when the cowl
is in place? Also, check the intercylinder baffles, to make sure that
they are properly installed. Any discrepancies in those areas will cause
the cooling air to bypass the cylinders and lead to higher temperatures.

Most production planes have very inefficient cooling, anyhow.


Not sure if you are responding to the OP or me, but my temperatures
(when I had the plane) were always low. And, yes the baffling was
correct. I am sure there were some "leaky" places.

--

Regards, Ross
C-172F 180HP
Sold
KSWI