Low CHT Temp on one cyl

[Mike5250]

Low EGT Temp on one cyl

I was flying a rental 172 this past weekend, older M model with penn yan 180hp conversion. I was messing with engine monitor and all EGT show 1100+ and cyl 3 shows 600 +/-. Of course I reported it.

What would cause something like this, besides a bad temperature sensor?


edit : egt!

 

[JOhnH]

I suspect you mean EGTs. Either that or your engine should have melted.

And (assuming it was EGT) it seems to me that ALL of your cylinders were running cold. How lean (or rich) were you running? What was the OAT.

Sometimes One cylinder will read lower than the rest if that cylinder has the original probe and the other three have the newer probes that came with the monitor.

 

[cirrusmx]

cyl 3 is usually at the back and gets the least airflow so CHT will be cooler. at least that is the case in the continentals. A low egt probably means that the cylinder cant be going through full combustion, or maybe the temp probe is broken, etc. You cant never know until you open it up.

 

[flyingmoose]

cyl 3 is usually at the back and gets the least airflow so CHT will be cooler. at least that is the case in the continentals. QUOTE]
I suspect you mean warmer?

Hard to say what could cause the issue, but without other symptoms I would say the EGT probe could be suspect.

 

[Mike5250]

Outside air temp was around 60F. I was running 2400-2500 rpms. We were 100-200 under gross and it was climbing 700-800 Fpm, and felt strong.

 

[bnt83]

cyl 3 is usually at the back and gets the least airflow so CHT will be cooler. at least that is the case in the continentals. A low egt probably means that the cylinder cant be going through full combustion, or maybe the temp probe is broken, etc. You cant never know until you open it up.

 

[RedHarris]

I was flying a rental 172 this past weekend, older M model with penn yan 180hp conversion. I was messing with engine monitor and all EGT show 1100+ and cyl 3 shows 600 +/-. Of course I reported it.

What would cause something like this, besides a bad temperature sensor?


edit : egt!

ooops

 

[Henning]

I was flying a rental 172 this past weekend, older M model with penn yan 180hp conversion. I was messing with engine monitor and all EGT show 1100+ and cyl 3 shows 600 +/-. Of course I reported it.

What would cause something like this, besides a bad temperature sensor?


edit : egt!

Fuel, either too little or too much in ratio with the air it was receiving. Did it run rough at all?

 

[flyingron]

Was it always this way? Do you have the same probe on that Cylinder. CHT's on my #3 (out of 6) is always lower because it has a spark plug gasket problem on it where all the others are threaded plugs (the threaded hole in #3 has the "original" CHT gauge probe in it).

 

[NoHeat]

An exhaust pipe leak near the header can cause a low egt on that cylinder. If that's the case, it would be unsafe to fly. A visual inspection would tell you.

If it is fuel injected, then maybe the one injector has a problem, making it much too rich or lean. Doing a very gradual lean at altitude (GAMI spread test) will tell you.

Otherwise, maybe a bad probe. Swapping probes would tell you.

If you owned the plane, these three checks would be easy and cheap. Don't know if the rental owner would care enough to do them, though.

 

[RV10flyer]

An exhaust pipe leak near the header can cause a low egt on that cylinder. If that's the case, it would be unsafe to fly. A visual inspection would tell you.

If it is fuel injected, then maybe the one injector has a problem, making it much too rich or lean. Doing a very gradual lean at altitude (GAMI spread test) will tell you.

Otherwise, maybe a bad probe. Swapping probes would tell you.

If you owned the plane, these three checks would be easy and cheap. Don't know if the rental owner would care enough to do them, though.

Agree with No heat...

Don't ever assume it is just a bad sensor. If the clamp breaks or someone forgets to reinstall one properly, your probe could be exiting the hole. 1,200-1,500F exhaust gases through an 1/8" hole can ruin your day. Always return to the airport and at least confirm they all are secure. If you actually had that large of an EGT span, you would feel it and would not get the 700-800 fpm climb that you normally get.

 

[comanchepilot]

Agree with No heat...

Don't ever assume it is just a bad sensor. If the clamp breaks or someone forgets to reinstall one properly, your probe could be exiting the hole. 1,200-1,500F exhaust gases through an 1/8" hole can ruin your day. Always return to the airport and at least confirm they all are secure. If you actually had that large of an EGT span, you would feel it and would not get the 700-800 fpm climb that you normally get.

I dunno about your preflight, but mine includes checking the egt and cht probes before the first flight of the day . . . and then monitoring the gauge the rest of the time . .

 

[RV10flyer]

I dunno about your preflight, but mine includes checking the egt and cht probes before the first flight of the day . . . and then monitoring the gauge the rest of the time . .

You cannot inspect them on my RV-10 without pulling top and bottom cowling. I do that at every oil change(50 hrs). My preflight of the engine area includes a flashlight inspection with a mirror through oil door and cowl inlets, flashlight up through cowl outlet, feel everything for security and oil level. I can see a lot but not all 6 egt probes. My GRT EFIS/EIS will warn me if EGT spread is > 100F. If I get that warning and everything else appears normal, then I would suspect wiring/egt probe failure or loose clamp. I will be pulling power way back, finding an airport to land and pull cowling off. It is a 30 minute job with a helper.

 

[Mike5250]

Fuel, either too little or too much in ratio with the air it was receiving. Did it run rough at all?

Ran smooth and seemed to have full power. We were below gross but 4 adults and a few hours of fuel so a loss in power would be more noticeable.

 

[Mike5250]

An exhaust pipe leak near the header can cause a low egt on that cylinder. If that's the case, it would be unsafe to fly. A visual inspection would tell you.

If it is fuel injected, then maybe the one injector has a problem, making it much too rich or lean. Doing a very gradual lean at altitude (GAMI spread test) will tell you.

Otherwise, maybe a bad probe. Swapping probes would tell you.

If you owned the plane, these three checks would be easy and cheap. Don't know if the rental owner would care enough to do them, though.

It is not fuel injected.

I am going to call them and see if any repairs were made. An issue like this might tell me more about how they handle maintenance on the rentals... Overall, they always seemed to care for the planes.

 

[Henning]

Ran smooth and seemed to have full power. We were below gross but 4 adults and a few hours of fuel so a loss in power would be more noticeable.

Haven't found the issue yet? Have you eliminated the sender/gauge from the situation by swapping 2 cylinders? Have you looked for an induction leak? I use starting fluid or WD-40 and spray the induction traces while running to see if it picks up a few RPM.

 

[flyingmoose]

Haven't found the issue yet? Have you eliminated the sender/gauge from the situation by swapping 2 cylinders? Have you looked for an induction leak? I use starting fluid or WD-40 and spray the induction traces while running to see if it picks up a few RPM.

I think OP was renting, so it would not be his doing.

 

[Henning]

I think OP was renting, so it would not be his doing.

Ahhh, well if he's a renter, WGAF, it's someone else's problem.

 

[Tony_Scarpelli]

Re: Low EGT Temp on one cyl

I was flying a rental 172 this past weekend, older M model with penn yan 180hp conversion. I was messing with engine monitor and all EGT show 1100+ and cyl 3 shows 600 +/-. Of course I reported it.

What would cause something like this, besides a bad temperature sensor?


edit : egt!

Mike,

Sounds like typical rental fleet crap! who cares if it destroys the engine. On the other hand you don't want it to fall apart while you or your family and friends are in the plane.

So I would recommend you go to harbor freight buy a IR thermometer for about $25-29. They are great.... It makes double checking the temps against the probes and between cylinders much easier and more accurate.

Cherokees run cold and in the winter time you should have a weatherization plate which blocks some of the air to help the engine to get to normal operating temps and allow the oil heat to get where it needs to be. This plate is a simple piece of aluminum that blocks some air frown in the front of the cowl.

You might recommend this to the fbo as it will help the engine run longer. Finally, double check your leaning procedure to make sure you are doing it correctly. You can use mixture to lower or raise the temps as needed.

 

[flyingmoose]

Re: Low EGT Temp on one cyl

Mike,

Sounds like typical rental fleet crap! who cares if it destroys the engine. On the other hand you don't want it to fall apart while you or your family and friends are in the plane..

They are not all junk, just because he had a squawk on a airplane? c'mon

So I would recommend you go to harbor freight buy a IR thermometer for about $25-29. They are great.... It makes double checking the temps against the probes and between cylinders much easier and more accurate..

What is he going to do? Take the cowls off and check it? How about just turn it into maintenance?
I recommend you don't spend a dollar on this. You already did when you rented it.

Cherokees run cold and in the winter time you should have a weatherization plate which blocks some of the air to help the engine to get to normal operating temps and allow the oil heat to get where it needs to be. This plate is a simple piece of aluminum that blocks some air frown in the front of the cowl..

Its not a Cherokee.

 

[Tony_Scarpelli]

Re: Low EGT Temp on one cyl

They are not all junk, just because he had a squawk on a airplane? c'mon

What is he going to do? Take the cowls off and check it? How about just turn it into maintenance?
I recommend you don't spend a dollar on this. You already did when you rented it.

Its not a Cherokee.

Cherokees and 172s often have the same engine/characteristics. I didn't want to write a book...... Cessnas run even cooler than Cherokees as evidenced by their excessive use of carb heat.....more so than Cherokees anyway.

Rental fleet is not all junk? Maybe but you can't tell by what I have seen. but this type of thing is very expected from the rental fleet junk.

If you fly rental fleet junk and you are too cheap to spend $25 to put a tool in your flight bag then that is ok with me. Like I said, who cares if the thing falls apart, just so long as it doesn't do it on my watch. What others do is their choice. Boneyards are full of people who roll the dice.

 

[RV10flyer]

Re: Low EGT Temp on one cyl

Cherokees and 172s often have the same engine/characteristics. I didn't want to write a book...... Cessnas run even cooler than Cherokees as evidenced by their excessive use of carb heat.....more so than Cherokees anyway.

Rental fleet is not all junk? Maybe but you can't tell by what I have seen. but this type of thing is very expected from the rental fleet junk.

If you fly rental fleet junk and you are too cheap to spend $25 to put a tool in your flight bag then that is ok with me. Like I said, who cares if the thing falls apart, just so long as it doesn't do it on my watch. What others do is their choice. Boneyards are full of people who roll the dice.

It was a large EGT spread, not CHT. No matter whether personally owned or rented, it needs further investigation.