EGT Sensors - cylinder 3 readings jumping

[AlexLev]

Hey all --

New owner here. Bought an M20G a few months equipped with a Aerospace Logic Egt-100-4 gauge. Cylinders 1/2 were not working when I bought the plane, they always displayed "cold." Cylinder 3 has been giving me some strange readings sometimes, when in cruise flight it will oscillate between 1150-1350 throughout the flight. The engine seems to perform well, but those readings have me concerned as I read somewhere that could be a sign of a failing exhaust valve. Cylinder 4 seems to stay steady between 1350-1400 depending on how I lean.

CHTs are all normal (different Aerospace unit) and don't change much during flight.

My thoughts are that I should probably see if the probes are working fine for CYL 3 before I investigate too much further and may as well fix cylinder 1/2 in the meantime as well so I can get full EGT readings.

- Who here has replaced EGT probes? If a mechanic does it, approx how much time does it take and what do the parts generally cost?

Any additional thoughts would be welcome!

Edited March 6, 2017 by AlexLev

[Guest]

It's unusual having 2 different brands providing info for 2 different systems.  From the Aerspace Logic systems I've dealt with the probes simply plug into the harness. You can open the plugs to make sure the connections are clean and tight.  If all is good there, I would start by switching probes or plugs around to isolate the fault.

Failing that buy probes for the G3 and removed the Aerspace Logic system.

Clarence

[Marauder]

Hey all --
New owner here. Bought an M20G a few months equipped with a Aerospace Logic Egt-100-4 gauge. Cylinders 1/2 were not working when I bought the plane, they always displayed "cold." Cylinder 3 has been giving me some strange readings sometimes, when in cruise flight it will oscillate between 1150-1350 throughout the flight. The engine seems to perform well, but those readings have me concerned as I read somewhere that could be a sign of a failing exhaust valve. Cylinder 4 seems to stay steady between 1350-1400 depending on how I lean.
CHTs are all normal (different gauge, plane has a Insight G3 for CHT) and don't change much during flight.
My thoughts are that I should probably see if the probes are working fine for CYL 3 before I investigate too much further and may as well fix cylinder 1/2 in the meantime as well so I can get full EGT readings.
- Who here has replaced EGT probes? If a mechanic does it, approx how much time does it take and what do the parts generally cost?
Any additional thoughts would be welcome!

Alex -- went through a similar situation with my JPI 900. The JPI EGT was jumping around in a similar fashion as your unit is. Periodically the JPI internal troubleshooter would put a "bad probe" message on the display. I ordered a replacement probe from Aircraft Spruce and went to replace it. When I looked at the connector fro the harness, I found the connector loose. All I needed to do was tighten up the connector and it has been fine since.

When I spoke with JPI, they said a failing probe would most likely just go open and not display a temp. Hopefully yours is as simple of a fix.


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[Marauder]

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[AlexLev]

9 minutes ago, M20Doc said:

It's unusual having 2 different brands providing info for 2 different systems.  From the Aerspace Logic systems I've dealt with the probes simply plug into the harness. You can open the plugs to make sure the connections are clean and tight.  If all is good there, I would start by switching probes or plugs around to isolate the fault.

Failing that buy probes for the G3 and removed the Aerspace Logic system.

Clarence

Sounds like a good idea to switch probes 3 and 4 and see if the problem is the probe or the actual cylinder.

[ArtVandelay]

The failing exhaust valve will result in a rhythmic sine wave like oscillation, if random then more likely a probe problem or poor connection with one of the plugs.

[AlexLev]

1 minute ago, teejayevans said:

The failing exhaust valve will result in a rhythmic sine wave like oscillation, if random then more likely a probe problem or poor connection with one of the plugs.

Well, it does go from 1100-1400 and then back down and back up, so it is sort of like a sine wave =\ usually between a couple hundred degrees F. Hoping it's still a poor probe though...it doesn't always do the sine wave, but on my most recent 4-hour cruise flight, it did that for a good few hours..

[kortopates]

Well, it does go from 1100-1400 and then back down and back up, so it is sort of like a sine wave =\ usually between a couple hundred degrees F. Hoping it's still a poor probe though...it doesn't always do the sine wave, but on my most recent 4-hour cruise flight, it did that for a good few hours..

Don't worry, that is not FEVA, but it is a loose connection or failing probe. As Clarence already said, dump the Aerospace unit and add EGT probes and add FF to your G2. Without download capability your wasting your time and $ on the other one.


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[neilpilot]

16 hours ago, AlexLev said:

Sounds like a good idea to switch probes 3 and 4 and see if the problem is the probe or the actual cylinder.

Exactly what I would suggest.  Also, if the probe leads are run in parallel close to each other, or run close to the alternator wiring or another wire with significant current, this could overwhelm the probe lead shielding and cause the unsteady probe readout you report.  I've installed Aerospace Logic EGT-100-4 in both of my Mooneys (under A&P supervision, of course), and in each case had to re-arrange some of the probe leads to eliminate interference.  The cold cylinders, OTOH, are most likely bad probes assuming the connectors are tight.

[AlexLev]

On 2/27/2017 at 10:12 AM, neilpilot said:

Exactly what I would suggest.  Also, if the probe leads are run in parallel close to each other, or run close to the alternator wiring or another wire with significant current, this could overwhelm the probe lead shielding and cause the unsteady probe readout you report.  I've installed Aerospace Logic EGT-100-4 in both of my Mooneys (under A&P supervision, of course), and in each case had to re-arrange some of the probe leads to eliminate interference.  The cold cylinders, OTOH, are most likely bad probes assuming the connectors are tight.

Late response here, but do you know what sort of probes I'd need to replace 1/2? They're not $180/each, are they? The ones I see on aircraftspruce are pretty pricey and I'm not sure if there are less expensive alternatives. It turns out I don't have a G2, just two different Aerospace Logic units. One for CHT and one for EGT. The CHT one is working fine.

Edited March 6, 2017 by AlexLev

[gsxrpilot]

I'd scrap both and install a G2 at your earliest convenience. As Paul says, without data download capability, both of those Aerospace gauges are of limited value. Engines are too expensive to overhaul/replace, to not know what's going on inside at all times.

[AlexLev]

1 hour ago, gsxrpilot said:

I'd scrap both and install a G2 at your earliest convenience. As Paul says, without data download capability, both of those Aerospace gauges are of limited value. Engines are too expensive to overhaul/replace, to not know what's going on inside at all times.

I hear you, it's more than I can afford at the moment but I would still prefer to fix the EGT sensor I do have so as to have some info in flight, even if it is not exportable.

[Guest]

7 hours ago, AlexLev said:

Late response here, but do you know what sort of probes I'd need to replace 1/2? They're not $180/each, are they? The ones I see on aircraftspruce are pretty pricey and I'm not sure if there are less expensive alternatives. It turns out I don't have a G2, just two different Aerospace Logic units. One for CHT and one for EGT. The CHT one is working fine.

They do prize their probes quite highly.  I would start with the simple before buying parts. Make sure that wires are not run near ignition or alternater wires.  With a few basic tools open the plug ends and check all of the screw terminals on the wire harness to make sure they are clean and tight.  if the problem persists switch a good and bad probe to isolate the fault.

Clarence

[neilpilot]

I have replacement probe info in my hangar, and can get you information when I fly home Friday. From memory I paid well under $100 each.

[AlexLev]

2 hours ago, neilpilot said:

I have replacement probe info in my hangar, and can get you information when I fly home Friday. From memory I paid well under $100 each.

Sounds good! I was looking at this probe: http://www.aircraftspruce.com/catalog/inpages/egtprobekit.php?clickkey=245125 but not sure which ones I can replace with.

And Clarence, thanks for the advice -- I have the plane in a shop now for an ADSB upgrade and I wanted them to look into it fixing the probes -- I'll talk with a mechanic later and see what they quote.

[jaylw314]

If I remember from Mike Busch's webinars, a failing exhaust valve may or may not be preceded by EGT fluctuations, and if it does it is usually +30-40 degF once a minute.

I did have an interesting failure mode in one of my EGT sensors.  It was reading about 200 degF too low on and off.  When I checked the probe, the probe body itself was loose in the clamp and could slide in and out of the exhaust pipe.  Only the wire harness placement kept it from falling out.  My A&P tightened the ferrule that holds the probe, no extra charge, and the EGT readings were back to normal.

[neilpilot]

On 3/6/2017 at 8:58 AM, AlexLev said:

Sounds good! I was looking at this probe: http://www.aircraftspruce.com/catalog/inpages/egtprobekit.php?clickkey=245125 but not sure which ones I can replace with.

And Clarence, thanks for the advice -- I have the plane in a shop now for an ADSB upgrade and I wanted them to look into it fixing the probes -- I'll talk with a mechanic later and see what they quote.

Just returned from a week on Hilton Head Island.  The Westach replacement probe that fits the ASL EGT-100 series is WES 712-2DWK, which Chief and others sell for $60 or less.

[carusoam]

Neil,

most importantly, How was Hilton Head?

It is a nice stop along the east coast on the way to SnF...

Best regards,

-a-

[neilpilot]

I've been going to Hilton Head for 27 years, and though it's out grown it's initial charm we still enjoy visiting. Just not in season. Expensive fuel but Signature waives handling and discounts 50 cents/gal weekends. $10/nite parking. 

[DXB]

On 2/26/2017 at 5:43 PM, Marauder said:

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Huh. I got the identical message for #3 before startup the last two flights. If I reset the JPI after startup, EGT on #3  subsequently works fine.  I saw nothing obvious wrong when I looked at the probe but will have to dig a little further to find where it links into the harness before ordering a replacement probe.  Any tips appreciated.

[Marauder]

Huh. I got the identical message for #3 before startup the last two flights. If I reset the JPI after startup, EGT on #3  subsequently works fine.  I saw nothing obvious wrong when I looked at the probe but will have to dig a little further to find where it links into the harness before ordering a replacement probe.  Any tips appreciated.

Follow the lead from the probe. There will be a connector underneath a sleeve. It has a screw, washer and nut sandwiching the probe and lead end (to the JPI unit) together. Check to make sure this is snug. That fixed my issue.

Could also be a loose pin in the connector that goes to the JPI. As I mentioned above, JPI says when a probe fails, it usually opens and doesn’t show a value again.


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[DXB]

14 hours ago, Marauder said:

Follow the lead from the probe. There will be a connector underneath a sleeve. It has a screw, washer and nut sandwiching the probe and lead end (to the JPI unit) together. Check to make sure this is snug. That fixed my issue.

 

Thanks - I passed along this advice to my Christmas Hangar Elf^TM this morning.  The two screw connections actually seemed pretty snug, so he loosened them, slathered the connectors and their crimp sites with Santa's Magic Liquid Semiconductor (aka Stabilant 22), and re-tightened.  Another Christmas aviation miracle!!

[DonMuncy]

1 hour ago, DXB said:

Thanks - I passed along this advice to my Christmas Hangar Elf^TM this morning.  The two screw connections actually seemed pretty snug, so he loosened them, slathered the connectors and their crimp sites with Santa's Magic Liquid Semiconductor (aka Stabilant 22), and re-tightened.  Another Christmas aviation miracle!!

Also be aware that JPI insists that the connectors washers be installed in a particular manner. If memory serves, the star lock washer goes between the two connectors.