Engine cooling

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8451
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Engine cooling

Post by 8451 » Mon May 20, 2019 8:16 am

I recently purchased a 120 and it is equipped with CHT for the two rear cylinders. While flying it I noticed one of them has the tendency to top 400 dF during climb, even if I try climbing at 85-90 MPH. Oil temperature remains in line during this time and CHT is fine in level flight. OAT was 32-33 dC on the ground.

The airplane had at one point spent several years of its life in Wisconsin before coming south, is there a chance there is some sort of winterization kit applied that may be heating things up? I noticed the manual notes a “summerization kit,” which as I understand it is a lip on the trailing edge of the bottom cowling which helps cooling - I noticed this lip tends to be present on other model airplanes of the same era.

Are there any suggestions as to how I may check to ensure my temperatures are controlled? I can look at the baffling but the issues only present themselves during climb; my initial impression is I may not gain much there.

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6643
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Re: Engine cooling

Post by 6643 » Mon May 20, 2019 9:06 am

C-85? The limit is 540 degrees. If the reading makes you uncomfortable, cover the gauge with something. ;)

(The summerization kit also includes inter-cylinder baffles.)

8451
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Re: Engine cooling

Post by 8451 » Mon May 20, 2019 11:20 am

6643 wrote:
Mon May 20, 2019 9:06 am
C-85? The limit is 540 degrees. If the reading makes you uncomfortable, cover the gauge with something. ;)

(The summerization kit also includes inter-cylinder baffles.)
Yes, C-85. I know the strength of aluminum drops off quickly above 400 dF, prompting my concern, certified redline notwithstanding.

8359
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Re: Engine cooling

Post by 8359 » Mon May 20, 2019 11:27 am

I've been thinking about this as well, I hit 400*F pretty easy in my O-290, however my oil temp never peaks 170-180*F. I know Mike Busch recommends no more than 400*F, but he is a self proclaimed longevity nut.

My concern is that my oil temp doesn't seem to be getting high enough. Lycoming recommends at least 185*F (up to 210*F) for oil operating temp in order to help burn off any moisture that gets into the oil. I've never been able to get it up that high. And I'm not sure I want to with my CHTs near 400*F.

Seems like an impossible task to me, maybe if I ditched the oil cooler.

4004
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Re: Engine cooling

Post by 4004 » Mon May 20, 2019 8:06 pm

Have you calibrated your oil temp system?

8342
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Re: Engine cooling

Post by 8342 » Mon May 20, 2019 8:11 pm

8451 wrote:
Mon May 20, 2019 8:16 am
I recently purchased a 120 and it is equipped with CHT for the two rear cylinders. While flying it I noticed one of them has the tendency to top 400 dF during climb, even if I try climbing at 85-90 MPH. Oil temperature remains in line during this time and CHT is fine in level flight. OAT was 32-33 dC on the ground.

The airplane had at one point spent several years of its life in Wisconsin before coming south, is there a chance there is some sort of winterization kit applied that may be heating things up? I noticed the manual notes a “summerization kit,” which as I understand it is a lip on the trailing edge of the bottom cowling which helps cooling - I noticed this lip tends to be present on other model airplanes of the same era.

Are there any suggestions as to how I may check to ensure my temperatures are controlled? I can look at the baffling but the issues only present themselves during climb; my initial impression is I may not gain much there.
What temperature is the other probe indicating?

It may be just an indication issue.

I would swap the probes around to see if it follows.

Rick

8359
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Re: Engine cooling

Post by 8359 » Tue May 21, 2019 1:48 am

4004 wrote:
Mon May 20, 2019 8:06 pm
Have you calibrated your oil temp system?
I have not, but it's on my list of things to do.

8451
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Re: Engine cooling

Post by 8451 » Wed May 22, 2019 11:33 am

8342 wrote:
Mon May 20, 2019 8:11 pm
8451 wrote:
Mon May 20, 2019 8:16 am
I recently purchased a 120 and it is equipped with CHT for the two rear cylinders. While flying it I noticed one of them has the tendency to top 400 dF during climb, even if I try climbing at 85-90 MPH. Oil temperature remains in line during this time and CHT is fine in level flight. OAT was 32-33 dC on the ground.

The airplane had at one point spent several years of its life in Wisconsin before coming south, is there a chance there is some sort of winterization kit applied that may be heating things up? I noticed the manual notes a “summerization kit,” which as I understand it is a lip on the trailing edge of the bottom cowling which helps cooling - I noticed this lip tends to be present on other model airplanes of the same era.

Are there any suggestions as to how I may check to ensure my temperatures are controlled? I can look at the baffling but the issues only present themselves during climb; my initial impression is I may not gain much there.
What temperature is the other probe indicating?

It may be just an indication issue.

I would swap the probes around to see if it follows.

Rick
Rick, one probe is indicating about 410-420, the other is about 360.

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5115
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Re: Engine cooling

Post by 5115 » Thu May 23, 2019 10:35 pm

Put both probes in boiling water and see if they both get to 212F.
There could be some good differences between the front cylinder temp and the rear ones.
Lots of things can affect cylinder temp. Baffling, cable or harness in the airflow, preventing proper back cylinders cooling, etc.
You need to know if both probes are good to start with.
Martin Tanguay
Intl Cessna 120-140 Association - Canadian rep
C140, C-FJAR, 1946, sn:9168, O-200, ragwings

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