Are engine monitor sensors consumable items?

[Jim_R]

I installed an Insight G3 engine monitor in March 2013 (10 years ago). I have a Tanis heater installed, so the CHT sensors are spark plug gasket-type instead of the normal bayonet (since the heater elements occupy those ports). The EGT sensors are typical bayonet-type probes in the exhaust tubing.

In 2019, the EGT 4 reading started to show occasional noise, but it was still usable. I lived with it for a while, but it continued to degrade and eventually became so erratic that it was useless. That sensor was replaced in Oct 2020.

After that, I had 4 solid CHT and 4 solid EGT readings...for one whole flight. The next day, the CHT 3 sensor started to show the same occasional noise that EGT 4 exhibited when it started to fail.

Within the last year, additional sensors have failed. As of today, CHT1, CHT3, and EGT3 are all unusable and slated for replacement. That's half of my sensors failed in 10 years.

My questions:
Does this sound like a typical failure rate for these sorts of sensors, or is this an unusually high rate of failure? (I don't hear a lot of people talking about replacing engine monitor sensors, but I don't know if that's because it's common/expected, like periodically replacing spark plugs, or if it's so rare it never comes up.)

Should I expect the remaining 4 sensors' failure is imminent, and just bite the bullet and replace them all now, or could they still have another 10 years in them?

 

[Mongoose Aviator]

What does the G3 diagnostic page show?

 

[Jim_R]

What does the G3 diagnostic page show?

I don't recall the details, but it confirms those sensors are bad.

 

[Jim_R]

This may or may not be related, but I have also seen the fuel flow readings change recently. It was never completely accurate out-of-the-box, but I eventually dialed in the K factor so that it was accurate and that lasted for several years. The plane sat for a long time during the pandemic, and somewhere around that time I started to notice the flow reading was much higher than it used to be. I have not tried to dial that back in yet. The timing of the FF rate change did not coincide with the timing of the CHT/EGT degradation.

 

[mondtster]

Occasional thermocouple failures due to heat and vibration are not uncommon. I wouldn’t lose much sleep over having to replace some from time to time, although you may want to look at the installation to see if things could be secured differently to promote a longer life.

 

[bradg33]

The short answer is yes. EGT probes probably moreso than CHT (the EGT probes live a really hard life), but you're gonna have to replace probes from time to time as they all live in a pretty harsh space. 10 years is a pretty good run, IMHO, for the probes.

 

[Ryan Klems]

Yeah, all these sensors eventually wear out. The FF sensor rotors eventually jam or fail in other ways and stop reading, EGT probes burn up, etc. Spark plug gasket CHT probes also live a hard life, as the gasket area gets work hardened by the reuse, the wires are typically getting abused a bit as you tighten or loosen the plugs work hardening them as well, etc. You might try a piggyback probe like https://www.aircraftspruce.com/catalog/inpages/chtTanisProbe1.php instead of the spark plug gasket ones (make sure to match thermocouple style), Tanis also makes a probe with dual heater and thermocouple probe (available in J and K and grounded and non-grounded ... to work with just about any setup).

 

[Jim_R]

OK, sounds like this is normal wear-and-tear, then. Thanks for the sanity check.

You might try a piggyback probe like https://www.aircraftspruce.com/catalog/inpages/chtTanisProbe1.php instead of the spark plug gasket ones (make sure to match thermocouple style), Tanis also makes a probe with dual heater and thermocouple probe (available in J and K and grounded and non-grounded ... to work with just about any setup).

Thanks for these tips! I looked on the Insight website, and sure enough they sell piggyback probes nowadays. I've got a question in to them to see if they recommend those over the plug gasket style...I know back when I opted for the gasket sensors they cautioned me that they would not be as accurate as the bayonet probes, so I'm guessing they'll suggest the piggyback probe now.