High EGTs on one cylinder

bflynn

bflynn

Final Approach
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Brian Flynn
The other night, one of the newer club members asked a couple of us about what higher EGTs mean in a single cylinder. He had a video from in flight, one cylinder was 1300+. Yikes. The temp dropped on downwind when he pulled the throttle back abeam the numbers.

my understanding is that it occurs because combustion is taking place in the exhaust. We referred him to the A&P and I identified it could mean an exhaust valve problem, but I started thinking more about this. What are the potential causes? Is a bad exhaust valve the cause or an effect? Too much fuel? Late ignition?
 
High EGTs compared to what? The absolute value of the EGT means little. Moving the probe slightly in the exhaust stack will change the value. Now, if this represents a increase in what the cylinder had read before or the point in which the EGT peaks, you might have a meaningful observation.
 
Could very well be a cylinder that’s running too lean due to an intake leak. Did the CHT rise as well?

I’d start by checking the intake runners and see if there’s any blue fuel stains. The Archer had a problem just like this. EGT ran high on #4. Had intake and exhaust gaskets that were in bad shape.
 
1300 is not high for an EGT, did you mean CHT? On the other hand, if you had a 1300F CHT, the cylinder probably would have melted. Bad probe?
 
First do a compression check to see if the valves are seating.
 
GeorgeC said:
1300 is not high for an EGT, did you mean CHT? On the other hand, if you had a 1300F CHT, the cylinder probably would have melted. Bad probe?
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Yeah. 1300 is what I would expect to see at cruise altitude with the mixture full Rich.
 
1300 is a relative value that is largely dependent on where the probes are mounted. If 1100 is/was a typical temp for that aircraft, and one cylinder has jumped to 1300, something has changed on the cylinder. Could be an induction leak, could be a misfiring plug. Could be lots of things. I wouldn’t be happy until I resolved the issue.
 
bflynn said:
The other night, one of the newer club members asked a couple of us about what higher EGTs mean in a single cylinder. He had a video from in flight, one cylinder was 1300+.
Click to expand...
As others have said, 1300 is not high, so if that cylinder has significantly higher EGT than the others, I'd suspect he needs to learn how to lean to burn fuel more efficiently.
 
I don't have the video, but the other cylinders were significantly cooler. I might be wrong about the 1300 number too. I haven't flown the warriors in a couple of years and the one he flew was the only one with a JPI.

He said he was leaned, but who knows.
 
bflynn said:
I don't have the video, but the other cylinders were significantly cooler. I might be wrong about the 1300 number too. I haven't flown the warriors in a couple of years and the one he flew was the only one with a JPI.

He said he was leaned, but who knows.
Click to expand...

Obviously if one cylinder is significantly different from the others, it would be reason to investigate. 1300F just seemed like a low number for EGT.

Not an A&P, but I’d think that starting with a compression check would be a good place to begin investigating

You said Warrior, so that would rule out an injector issue. I’ve seen EGT spikes in an airplane with a clogged injector.
 
Right, carbureted engine. Shouldn't trust my memory on things I didn't look at too closely.

It looks like the plane got grounded to be checked out.
 
1300 EGT is not significant in and of itself but if it's a change from a lower temp all the sudden then I would be concerned. If You came to me with the problem I would need to know that info. If you didn't know before we went for a flight I would check the placement of the probes and insure they are all installed the same distance from the flange bolted to the head. A small difference can make a big difference. Is that EGT higher than the others at idle or just high power settings? A good visual inspection is also in order to check for obvious fuel stains and security of all three primer lines. Obviously no one can troubleshoot it over the net but can give you advice as to what to look for and gather as much info as you can before engaging a mech. BTW I am an A&P and a higher than the other EGT isn't always a problem unless it's a change from previous operations so if it's a rental or club plane talk to some other frequent flyers and go from there.
 
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