Higher than normal EGT

Swampfox201

Swampfox201

Line Up and Wait
Joined
Aug 24, 2010
Messages
589
Display Name
Display name:
Todd W.
For a couple months every year I fly survey flights for a company. The 172 they use had a new motor installed last year as the old one was at TBO.

The new motor has been running fine until last week when the EGT gauge showed higher than normal. It used to run at the 11 o’clock position. Now it runs at 12-1. Otherwise the engine seems to run ok to me but the other pilot who fly’s thinks it runs a little rough.

They had maintenance look at it last week and they said the accelerator pump had a leak which wasn’t letting the fuel atomize correctly. They supposedly fixed it but the EGT is still high.

Anyone have an idea why this is? Sorry I don’t have the specs on the motor. It’s not fuel injected. The plane has carb heat. The picture shows where the EGT was running yesterday.

dd427ddf1665f6733fd627568f6a9b08.jpg



Sent from my iPhone using Tapatalk
 
Start with simple things first. 1) Intake leaks (causes leaner mixture) - loose stud nuts or bad gasket, intake pipe coupling worm clamps. 2) All primer lines secure and fuel lines (visual and check tightness) 3) Carb secure 4) Clean EGT probe and secure connections. 5) Believe it or not - mag timing and depending on how many hours if timing keeps slipping - mag cam getting worn. 6) Check carb heat valve/door for correct opening. No partial allowed.
Start with the first four!
Assuming mixture control friction lock is set.
Assuming correct spark plugs.
 
Last edited:
Or the simplest of all...bad gauge.
 
There is no such thing as EGT "too" high. All EGT engine operating techniques are taken from peak. How has that changed?
 
kgruber said:
There is no such thing as EGT "too" high. All EGT engine operating techniques are taken from peak. How has that changed?
Click to expand...

What has changed is the EGT gauge is reading higher than before after leaning the engine at altitude.
 
kgruber said:
Has the fuel flow changed?
Click to expand...

Not sure. There isn’t anything besides fuel gauges on the airplane and the FBO fuels the plane after I leave. It’s something I can check into tho.


Sent from my iPhone using Tapatalk
 
All it takes is for the resistance of the EGT lead to the gauge to change its resistance a tiny bit, and that happens at their screwed-together connections. As Kgruber says, there is only peak EGT, whatever the gauge says. That's why there's no numbers on the gauge. And I bet that reading is going to fluctuate over time as the suspect connection moves around.

But that accelerator pump leak needs fixing. It dribbles extra fuel up one side of the carb bore, makng one or two cylinders richer and causing that roughness. We had that in a factory overhauled engine, and it was because one of the pump's check ball springs was missing.
 
"My" experience with EGT is that the probes are troublesome and don't always last all that long. I replaced the probe in my single point EGT in my Cherokee 180C, and it lasted 5 years. When I replaced the entire exhaust last year, I figured the single point EGT was so unreliable.....that I didn't even drill a new hole for the probe. I'd like a cool 4 cylinder CHT/EGT setup................but my airplane cash went to ADS-B.
 
You must log in or register to reply here.
Back
Top