Rich Posted March 18, 2014 Report Posted March 18, 2014 Good Afternoon, I researched the archives to see my last post and replies on this subject. This is the second probe that has gone bad, both on the #3 cylinder. Has anyone else experienced this? The probe is placed 100MM from the cylinder as per Rotax instructions. It's located on the bend in the pipe. Just seems unusual to me.
Rich Posted March 18, 2014 Author Report Posted March 18, 2014 BTW, First probe went bad at approx. 110 TT. The second at 145 TT.
Anticept Posted March 18, 2014 Report Posted March 18, 2014 Are they being burned through, or are they still completely intact? Do you have a milli-ammeter to check them? You can have someone with a lighter heat the end as you check the miliamps, it will rise as it gets hotter.
Dan Kent Posted March 18, 2014 Report Posted March 18, 2014 Hey Rich, I have over 200 hrs on mine and no problems so far.
Rich Posted March 18, 2014 Author Report Posted March 18, 2014 Anti, Dave Thanks for the replies. They're intact and I'll check with the meter.
Anticept Posted March 18, 2014 Report Posted March 18, 2014 I ask because it could be your connectors too. I had a set that had corrosion set in, and moving the connector was enough to get it working for a while.
gisurvey Posted March 19, 2014 Report Posted March 19, 2014 My both EGT probes failed, left one aprox. 400h/5years, the right one 450h/6years. Consider consumables. Alec
Anticept Posted March 19, 2014 Report Posted March 19, 2014 Gisurvey's sounds more reasonable. And yes, EGT probes are consumables. We're putting them in a 1500+ degree airstream.
Rich Posted March 19, 2014 Author Report Posted March 19, 2014 Yes, I'm okay with that but my failures were at approx. 110 hrs. TT and again at 145 TT. Much different than the 400-450 / 5&6 year period And both on the same cylinder. That can't be the norm. Burning 93 octane mogas. They always operate in cruise around 1350-1400 degrees F.
Anticept Posted March 19, 2014 Report Posted March 19, 2014 It's probably a fluke that it happened. I still have not been informed if your probes are still intact, or melted away. The important thing with EGT placement is that you position them evenly from the exhaust valves. EGT is not a direct measurement of performance, it's relative. Having two of them is a good thing on the dual carb ULS because it helps determine if the carb balance is drifitng.
Rich Posted March 19, 2014 Author Report Posted March 19, 2014 Anti, Mentioned in my previous post that all are 100mm from the heads and it was in tact. No melting or abnormal look. I hope your right in that it's just a fluke. There are four EGT probes. Two CHT probes on my engine. 912ULS. Tru Trak sent another probe which I received today.
Anticept Posted March 19, 2014 Report Posted March 19, 2014 Oh, yeah you did say they are intact. Sorry (:
GlennM Posted March 20, 2014 Report Posted March 20, 2014 Bad batch of TCs? There are numerous ways they can fail. I can't remember if they have a brazed joint on these. I have had many fail at brazed joints on other types of TCs.
Runtoeat Posted March 20, 2014 Report Posted March 20, 2014 My right side EGT temp readout became intermittent and then went to zero. My mechanic removed the probe and checked connections and reinstalled it. It then started working again. Notice that it is now intermittent again and needs to be inspected. Don't seem to have this problem with the left side.
Anticept Posted March 20, 2014 Report Posted March 20, 2014 Runtoeat: the wires are loose or burned up which lead into the mating surfaces of the two metals. This can happen. Speaking of which, Rich, maybe that's the issue? Poor routing and anchoring of the wires leading to the EGT?
Rich Posted March 20, 2014 Author Report Posted March 20, 2014 Anti, The routing follows the previous routing through a sleeve so I'm almost sure that's not the problem. The connection at the junction of the probe is something I'll look at. I'll see if I can cut it open without damage to inspect the junction of the wires at the probe. Thanks for the idea and thanks to all for your input.
Anticept Posted March 21, 2014 Report Posted March 21, 2014 The engine vibrates quite a bit, I leave the last couple inches of my probe in free air, and anchored in a way that lets the wires flex.
Runtoeat Posted March 22, 2014 Report Posted March 22, 2014 Kurt, good info. Will take apart the probe and it's leads to have a look. Thanks. I know that there's a post elsewhere here about the correct replacement EGT probe. Anyone recall what the correct probe replacement is and best place to buy? Recall Aircraft Spruce was recommended.
Anticept Posted March 22, 2014 Report Posted March 22, 2014 I should take a picture to show what I mean. The wires are secured from vibration, but I leave a *small* loop at the end to keep tension off the probe.
gisurvey Posted March 22, 2014 Report Posted March 22, 2014 EGT, 0.75-1.25" Hose Clamp 10-01844 https://www.aircraftspruce.com/catalog/inpages/dynonsensorsdynon.php
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