CHT's on a Cherokee 140

[John221us]

Has anyone flown with an engine monitor on a Cherokee 140? My #3 CHT is 20 to 30 degrees higher than #4, the next highest and is running just north of 400 in cruise. It is a new cylinder with about 17 hours and I installed the engine monitor shortly after that, so I don't know what normal is. I have read a couple of references that says #3 will run 20 to 30 degrees hotter on Cherokees and this is normal. But one or to posts on a board is not definative. Do I just need to give it more time to break in or is this just normal for the plane? If it is already above 400 (404 to 414) in cruise, what will summer look like? I have read that the target is 380 and you don't want it above 420.

 

[murphey]

Has anyone flown with an engine monitor on a Cherokee 140? My #3 CHT is 20 to 30 degrees higher than #4, the next highest and is running just north of 400 in cruise. It is a new cylinder with about 17 hours and I installed the engine monitor shortly after that, so I don't know what normal is. I have read a couple of references that says #3 will run 20 to 30 degrees hotter on Cherokees and this is normal. But one or to posts on a board is not definative. Do I just need to give it more time to break in or is this just normal for the plane? If it is already above 400 (404 to 414) in cruise, what will summer look like? I have read that the target is 380 and you don't want it above 420.

John - welcome to my world. I've got a cherokee 180 and immediately after the overhaul (and new cylinders) I was seeing 475 at takeoff on #3 and over 400 in cruise in the Colorado fall and into the winter.

In cruise, a 20-30 deg difference (as long as in the 300s) isn't a problem, I've been told by many reputable folks here (Tom-D among others) and other places. Remember that an old lycoming carb engine isn't a finely tuned racecar engine and you'll never see everything at the same temps.

One item to look at now, and the cheapest, is the baffling. If you got lots of holes, then the cooling flow may not be really good around #3.

In theory, cylinder breaks in at 5-10 hours, but it's not unusual to see CHT fluctuations for 20-30 hours, so I've been told. The shop that did the overhaul told me to fly it 50 hours and then call them back. At 50 hours it was just as bad as the first flight and there were more problems.

Needless to say I will never recommend the shop and suspect they may be going out of business in the near future.

Unpaid advertisement: Charlie Merlot (Zephyr) quoted me a very reasonable and competitive price, and for other reasons (which I now regret) went with another shop. Stupid me.

If you're of a mind, have the cylinder borescoped by a reputable shop (about an hour of billable time) and see if there's any rust (not minor surface corrosion but serious rust), condition of the piston and if the rings are ok. You're in a more humid environment than I am, but they found rust on all 4 of my cylinders. The answer was re-hone (remove the rust) and install new rings. I'll be looking to see what the engine monitor reports in May when it starts getting warm around here.

 

[Bob Noel]

I had an engine monitor in my 140. but caveat: I'm not an A&P, I was just an owner.

1) Calibrate the sensors. That is, put the four of them in boiling water and/or heat some oil (at the same time) and note the variation between them.

2) If the sensors are really that accurate, then check the baffling to improve the airflow to #3

I was happiest keeping the CHT's right around 375 in cruise. However, having one run a little hotter but still way way below 500 doesn't sound bad. I almost never had all four with the same number of bars in CHT.

 

[Jay Honeck]

Any CHT over 400 degrees in a normally aspirated Cherokee is cause for investigation, IMHO. Our 6-cylinder O-540 rarely tops 400 on any cylinder, in climb, on the hottest day in South Texas.

 

[John221us]

John - welcome to my world. I've got a cherokee 180 and immediately after the overhaul (and new cylinders) I was seeing 475 at takeoff on #3 and over 400 in cruise in the Colorado fall and into the winter.

In cruise, a 20-30 deg difference (as long as in the 300s) isn't a problem, I've been told by many reputable folks here (Tom-D among others) and other places. Remember that an old lycoming carb engine isn't a finely tuned racecar engine and you'll never see everything at the same temps.

One item to look at now, and the cheapest, is the baffling. If you got lots of holes, then the cooling flow may not be really good around #3.

In theory, cylinder breaks in at 5-10 hours, but it's not unusual to see CHT fluctuations for 20-30 hours, so I've been told. The shop that did the overhaul told me to fly it 50 hours and then call them back. At 50 hours it was just as bad as the first flight and there were more problems.

Needless to say I will never recommend the shop and suspect they may be going out of business in the near future.

Unpaid advertisement: Charlie Merlot (Zephyr) quoted me a very reasonable and competitive price, and for other reasons (which I now regret) went with another shop. Stupid me.

If you're of a mind, have the cylinder borescoped by a reputable shop (about an hour of billable time) and see if there's any rust (not minor surface corrosion but serious rust), condition of the piston and if the rings are ok. You're in a more humid environment than I am, but they found rust on all 4 of my cylinders. The answer was re-hone (remove the rust) and install new rings. I'll be looking to see what the engine monitor reports in May when it starts getting warm around here.

My shop is checking the baffling today. On my way to Big Bear (3 hours at around 9,500) #3 was at 404 and #4 was at 382 (full throttle, but leaned to 100 ROP). On the way home (3 1/2 hours at 6500 and also tested 8500) #3 was 414 and #4 was 357 (I did end up pulling it back to get it cooler, down around 400, but lost 5 to 7 KTS). The other two were significantly cooler, but I don't remember the exact temperatures. On climb, I have been babying it a bit after initial climbout and keeping it under 430, but if I don't baby it, #3 will go up to 450. It has improved a bit after the first 8 or 9 hours, so maybe this is where it is going to be?

 

[John221us]

Any CHT over 400 degrees in a normally aspirated Cherokee is cause for investigation, IMHO. Our 6-cylinder O-540 rarely tops 400 on any cylinder, in climb, on the hottest day in South Texas.

I have read one or two posts on the Piper board, that this is normal for a Cherokee 140 on #3 and has to do with the fin placement on the cylinder, but this is only one reference. That is why I am specifically interested in experience with a Cherokee. I have read the stuff from Pelican and others and am aware that over 400 is not considered good (hence my concern).

 

[Jay Honeck]

I have read one or two posts on the Piper board, that this is normal for a Cherokee 140 on #3 and has to do with the fin placement on the cylinder, but this is only one reference. That is why I am specifically interested in experience with a Cherokee. I have read the stuff from Pelican and others and am aware that over 400 is not considered good (hence my concern).

Sorry, I wasn't clearer. My O-540 is in a Cherokee Pathfinder. Same basic design, just two more cylinders.

I also owned a Warrior for four years, but all I had in that plane was a single-probe EGT. No way to know what my CHTs were back in the "olden days". (Sometimes I think we were all better off not knowing....)

 

[EdFred]

My shop is checking the baffling today. On my way to Big Bear (3 hours at around 9,500) #3 was at 404 and #4 was at 382 (full throttle, but leaned to 100 ROP). On the way home (3 1/2 hours at 6500 and also tested 8500) #3 was 414 and #4 was 357 (I did end up pulling it back to get it cooler, down around 400, but lost 5 to 7 KTS). The other two were significantly cooler, but I don't remember the exact temperatures. On climb, I have been babying it a bit after initial climbout and keeping it under 430, but if I don't baby it, #3 will go up to 450. It has improved a bit after the first 8 or 9 hours, so maybe this is where it is going to be?

Lean it more.

 

[Ted]

Any CHT over 400 degrees in a normally aspirated Cherokee is cause for investigation, IMHO. Our 6-cylinder O-540 rarely tops 400 on any cylinder, in climb, on the hottest day in South Texas.

Yeah, but I remember you telling me at Osh a few years ago your fuel consumption numbers, which were very high.

 

[slacktide]

It would be interesting to know, from all who have reported their typical operating CHTs, what brand & model engine analyzer you have installed, as well as what type of probe, if you know it.

There has been a lot of discussion regarding this on the Grumman mailing list, suggesting that JPI tends to read higher than EI for the same installation.

 

[murphey]

It would be interesting to know, from all who have reported their typical operating CHTs, what brand & model engine analyzer you have installed, as well as what type of probe, if you know it.

There has been a lot of discussion regarding this on the Grumman mailing list, suggesting that JPI tends to read higher than EI for the same installation.

Verrrrry interesting about the JPI v EI. After the 15 months of aggravation and far too much money after paying for the overhaul, I'm seeing cruise CHTs (altitude 6.5-8.5 MSL) across the board 340-370. But then I haven't had a chance to fly in hot weather yet. Haven't gotten 10 hours on the new work either, but once broken in my normal cruise is 9.5-12.5 MSL.

Monitor: JPI 730
Probe: CHT probe, not the sparkplug version.
Engine: Lycoming O360-A4A

 

[John221us]

It would be interesting to know, from all who have reported their typical operating CHTs, what brand & model engine analyzer you have installed, as well as what type of probe, if you know it.

There has been a lot of discussion regarding this on the Grumman mailing list, suggesting that JPI tends to read higher than EI for the same installation.

Mine is an Insight G1 and whatever probes came with it.

 

[Bob Noel]

It would be interesting to know, from all who have reported their typical operating CHTs, what brand & model engine analyzer you have installed, as well as what type of probe, if you know it.

There has been a lot of discussion regarding this on the Grumman mailing list, suggesting that JPI tends to read higher than EI for the same installation.

Cherokee 140, with GEM 602, with the standard CHT and EGT probes (e.g., not the CHT probe on the sparkplug)

 

[el con]

I have a Cherokee 180.
Recently overhauled,(150 hrs now) #3 is always the hot cyl. #1,2,4 are always 299-310, #3 is 20-25 higher in normal flight at 2,500 rpm. #3 only hits 360-365 on a hot day in serious climb.
New Big Alaska baffling installed with silicone seals at overhaul.
Electronics Intl. US-8A EGT/CHT analyzer.
I don't lean a lot unless above 5,000 ft.

 

[John221us]

If you're of a mind, have the cylinder borescoped by a reputable shop (about an hour of billable time) and see if there's any rust (not minor surface corrosion but serious rust), condition of the piston and if the rings are ok. You're in a more humid environment than I am, but they found rust on all 4 of my cylinders. The answer was re-hone (remove the rust) and install new rings. I'll be looking to see what the engine monitor reports in May when it starts getting warm around here.

We are pretty dry here in Sac (no humidity to speak of), but we did get a bunch of rain recently. I do hangar the plane and don't fly when it is wet (I am VFR only). You think it might be rust? I will run it by my A&P.

 

[murphey]

We are pretty dry here in Sac (no humidity to speak of), but we did get a bunch of rain recently. I do hangar the plane and don't fly when it is wet (I am VFR only). You think it might be rust? I will run it by my A&P.

I live in Colorado, pretty dry here, and my cherokee is hangared. And I had serious rust on all 4 cylinders. Just another data point.

 

[Jay Honeck]

Mine is a JPI EDM-700. The CHT probes are the kind that fit under the spark plug (replacing the washer) because my engine has cylinder heaters.

Which I certainly no longer need.

 

[Tony_Scarpelli]

We did work on a cylinder in my Cherokee. We had a single prob CHT and the temps were showing 50 d F higher. After 10 hrs we pulled the probe boiled it in water and tested the output and found it putting out more voltage than it was supposed to. So we just calibrated it from then on.

For $29 you can buy an IR thermometer and immediately after shut down or upon run up check your cylinder head temps manually. If you do not have much difference in the questionable cylinders you can know that the probes require calibration.

With all the cheap **** we are getting from China we are going to see much more of this sort of thing. Get used to it.