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Dynon EGT probe failure (x4)

Jamie

Jamie

Well Known Member
On the way home from Sun-n-fun I noticed my #2 EGT went down to 600F. The temp would then fluctuate wildly and eventually it just dropped down to -99F, so obviously the problem was a bad probe.

I ordered a new probe from Dynon and when I pulled the old one, I noticed that the probe had actually burned off. At first I thought it was broken, but upon closer inspection it was burned through and only two little wires were sticking out of the nub.

I pulled the other three to see what they looked like, and all of them were burned off with only little wires hanging off of them and a little piece of metal holding the two wires together.

I did take pictures of the probes but I left my camera at the airport. I will get the camera tomorrow and upload photos and post them to this thread.

Has anyone else seen a failure like this? I asked around here and no one around here has EVER seen a failure like that in EGT probes, including two IAs I know that are top-notch guys.

I always lean to about 1400F. Probe holes are drilled approximately 2 inches from the top. I have 250 hours on the plane.

I have done a search on Dynon's forums and apparently they say that failure after 200 hours isn't unheard of. They say that any K-type EGT probe will work. Does anyone have any recommendations for some different probes that may last a little longer? I'm all about minimizing maintenance items if possible.
 
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almost same problem with EGT

Hi Jamie,

Had almost the same problem here in my RV7. After 80 hours TT in the hobbs, in the middle of a 1.5hours flight all my EGTs started reading about 700F degrees, as all other parameters in my dynon and backup instruments(including CHT oil pres and temps) seems ok,so i finished my flght into home, when landed, took the probes out and everything seems ok. A friend of mine who was a mechanic sugested me to check wires and connections. Everything is ok. He says that the only possibillity was a Dynon malfunction. As i am from brazil and far away from dynon support, i continued flying ultil had opportunity to take the unit to usa myself. Suddenly, after 6 hours after the problem begins, the EGT starts operating normally, again in the middle of a flight, and reading the temps around 1400F. I never know what the problem was. Now i have 22 hours after the problem happened and its working like a swiss clock.

Ghost things.....

Henrique
 
Burned off?

I would almost say this is a joke right?..Wow never heard of such a thing happening.

Where is 1400F out of interest..i.e how many degrees F rich of peak is that?..Are you gettiing into the detoation zone possibly and the resulting pressure pulses maybe eroding the probes away?

50F ROP is the risky area I believe.

Yeah its a long shot theory!

Frank
 
No Frank, no joke at all. They are literally burned/eroded away. Peak for me is around 1520F.
 
Years ago, when single-cylinder EGT's were the new-fangled rage, I remember that people failed/burned up EGT probes all the time. It was just assumed they were disposable/consumable.

I figured that today's reliability came about through years of engineering tweaks - I have 900+ hours on mine, and they are fine...well, I haven't actually LOOKED at them...!
 
Webb said:
Installation manual warned that installing too close to the engine would shorten the life of the probes.
Click to expand...

I just looked at the latest EMS installation manual and they recommend a position 2 to 8 inches down. I see no admonitions in the manual about installing the probes too close to the cylinder.

I believe that my probes are actually a little more than 2 inches away. I'll measure again tomorrow to get a more accurate number. Still, it doesn't make sense that the probes being too close would be causing them to burn due to temps. Again, look at my EGT #'s...they're not that high. Seems like if the probes were getting too hot....that would be reflected in the instrumentation on the EMS.

At what distance do other folks have their EGT probes mounted?

Just trying to think a little outside of the box here...

I get the popping when I throttle back aggressively. My understanding is that the popping is occurring because unburned fuel is getting in the exhaust and igniting. I am curious if this could be burning up the probes?

I guess if this WERE true....I could throttle back aggressively and watch my EGTs. They should actually climb when the popping is occurring if that is causing the problem, right?. I have to admit, I don't really watch the EGTs when throttling back.

Who knows...maybe I'm waaaay off base here.....
 
Jamie said:
...I guess if this WERE true....I could throttle back aggressively and watch my EGTs. They should actually climb when the popping is occurring if that is causing the problem, right?. I have to admit, I don't really watch the EGTs when throttling back.

Who knows...maybe I'm waaaay off base here.....
Click to expand...

Jamie,

Try downloading the data from the EMS and take a look at your EGT's. You might find something interesting in there. Then again, maybe not.
 
N941WR said:
Jamie,

Try downloading the data from the EMS and take a look at your EGT's. You might find something interesting in there. Then again, maybe not.
Click to expand...

Good idea Bill. I always fly with datalogging enabled. I will take the laptop tomorrow and give it a try.
 
KS Avionics (www.ksavionics.com) makes the best EGT probe, and have a very low failure rate. The probe tip is made out of Inconel, which is an excellent nickel alloy for high temp applications. A few of the EFIS vendors provide these probes with their units. I used to have Westach probes in the -6, and kept burning them up until I switched to these.
 
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Bob:

That's sort of what I was looking for. Dynon says that their EMS will work with any "K-type" probes...whatever that means. I will have to do more research to see if these probes are compatible.

As promised, here are some photos of the probes:

Of course this is a new probe:
DSC00027.JPG


This is the probe that was on exhaust for cylinder #2:
DSC00030.JPG


This probe was on one of the other cylinders:
DSC00029.JPG


Note that the outer shell is completely gone. The remaining probes still work....BUT...the temps are different from the new probe. The older probes will read higher temps than the newer probes and they are much more "sensitive". In other words, with the older probes it takes very little mixture change to effect a large change in displayed EGTs.
 
Jamie,
Check to see if the nuts are tight on your intake tubes (the ones on the cylinder head) These often need tightning (again) after OH/new.
 
How timely

Jamie, I just had my Dynon probe on #1 do the exact same thing. Mine are also located 2 inched down. I'll pull the other 3 out and have a look see.
 
As a point of reference, I measured mine yesterday to see how far down they are and the holes are 2.75" down.
 
J and K refer to the type of wire used in the probe. So if memory serves me K wire produces a signal in the range of temps found in our exaust and J wire produces a signal in the temp range of our cylinder heads. There is a wide range of thermocouple wire most all with a letter designation for uses in such things as furnaces and kilns and other uses such as refridgeration. An interesting point is that it is entirely possible to make our own probes using wire that is fairly easily gotten, the wire is just expensive as all get out. Also exaust gases are fairly corrosive and depending on how long yours were run it's not unreasonable to expect to change them once in a while. You got them from Dynon but is it really fair to Dynon to say it's a problem with a Dynon probe, I doubt they actually put the thing together.
 
Would it be possible for someone with Dynon-supplied (note that I didn't say Dynon-manufactured) probes to pull them when you get a chance? Only takes a couple of minutes once the cowl is off. I would be especially interested if you have 225+ hours on the plane.

Dynon basically believes that I am the only person with this problem. My personal belief is that this is happening on other installations but people don't realize it because the probes are continuing to function. I mean really, how many people do you know that pull EGT probes at annual to check them out?

I can't believe I would be the only person with this problem.

Thanks,
Jamie
 
Jamie said:
Would it be possible for someone with Dynon-supplied (note that I didn't say Dynon-manufactured) probes to pull them when you get a chance? Only takes a couple of minutes once the cowl is off. I would be especially interested if you have 225+ hours on the plane.

Dynon basically believes that I am the only person with this problem. My personal belief is that this is happening on other installations but people don't realize it because the probes are continuing to function. I mean really, how many people do you know that pull EGT probes at annual to check them out?

I can't believe I would be the only person with this problem.

Thanks,
Jamie
Click to expand...


Jamie, you are not the only one....I just had the same problem. It happened last week with less than 100 hours total time. My #1 egt suddenly started reading -99 then did as yours. and did as yours, would read back up to a normal egt then drop down to 600-700. My probe looks exactly like yours. My probes are mounted according to their install instructions. I run my egt's under 1400. I'm wondering if Dynon just got a bad batch of probes.
 
BlackRV7 said:
Jamie, you are not the only one....I just had the same problem. It happened last week with less than 100 hours total time. My #1 egt suddenly started reading -99 then did as yours. and did as yours, would read back up to a normal egt then drop down to 600-700. My probe looks exactly like yours. My probes are mounted according to their install instructions. I run my egt's under 1400. I'm wondering if Dynon just got a bad batch of probes.
Click to expand...

Very good info, Dana. Did you happen to check your other probes to see if they are doing the same thing?
 
Jamie said:
Would it be possible for someone with Dynon-supplied (note that I didn't say Dynon-manufactured) probes to pull them when you get a chance? Only takes a couple of minutes once the cowl is off. I would be especially interested if you have 225+ hours on the plane.

Dynon basically believes that I am the only person with this problem. My personal belief is that this is happening on other installations but people don't realize it because the probes are continuing to function. I mean really, how many people do you know that pull EGT probes at annual to check them out?

I can't believe I would be the only person with this problem.

Thanks,
Jamie
Click to expand...

I just replaced # 3 with ONLY 85 hrs TT . I will check the the others this weekend .
 
Just ask any AFS owners if they've ever had to change EGT's...they OEM the KSAvionics probes with their systems. All EGT probes are K-type.
 
rocketbob said:
Just ask any AFS owners if they've ever had to change EGT's...they OEM the KSAvionics probes with their systems. All EGT probes are K-type.
Click to expand...

That's good to know, Bob!

I basically just want to make 100% sure that it really isn't something unique to my install before I go and spend $300.00 on probes! I'll definitely be giving KS avionics a call.

Jamie
 
From my perspective, this failure is something of an anomaly. I think we've sold hundreds of Dynon EGT probes and I can count on my fingers the number of failure's we've seen over the years. In fact, across all of the mfgrs, failures are extremely rare....

Naturally it's not unheard of, but it's far from common. Our experience with the Dynon products have been very good from a reliability perspective, but so have most of the products we sell!

Just my 2 cents as usual.

Cheers,
Stein
 
Stein:

I appreciate the input. Seriously, I value your experience and perspective on the issue.

I have been incredibly happy with my Dynon products and they haven't skipped a beat since first flight (well, other than the AP, but that's another topic entirely. :)).

Anyway...

In this thread Dana has said that he has seen the same problem. The guy on my home field has had a failure in the same manner. The support fella at Dynon, after telling me multiple times that they've never had a failure like that and that EGT probe failures are almost unheard of, tells me that he's holding an EGT probe that a customer sent in that failed in exactly in the same manner as mine :confused:. So obviously it's not a complete fluke. Rare, perhaps but not a one-time occurrence.

I will reiterate that I believe it is happening a lot more than is being reported simply because the probes are continuing to work because the thermocouple weld is holding up. Perhaps if this thread gets enough attention and/or circulation people will be apt to pull their probes and check them out.

Perhaps I got a bad batch. Perhaps it's something particular to my install (although I've not heard even one suggestion on here regarding what exactly that problem could be other than the probes being mounted too close to the cylinder, which they're not).

Also (to me this is the most troubling part), after reviewing my records I see that I purchased my Dynon products in August 2006. The warranty period is supposed to be three years.

The last word I heard from Dynon is that they will not honor their warranty on their probes because "there is something wrong with my install", even though they can't tell me exactly what is wrong or what could possibly be causing the probe failures. The probes are installed per their instructions. Oh well. I have to admit that for the first time as a Dynon customer I'm a little disappointed that they would even consider a refusal of a probe warranty claim.

I have ordered $300.00 :)eek:) worth of probes from KS avionics. To me knowing that I have the best probes in there is worth the money. THEN if I burn them up...well....ok now I have a real problem. These probes have a two year/1000hr warranty. Hopefully they will work with my install and my EMS harness.
 
Hi Jamie,

I understand your frustration, and agree that it's might not necessarily be an isolated incident. I just wanted to give people the other side of the coin from my standpoint. We have replaced probes, yes - but rarely.

Did you buy your Dynon from me? If so, we'll take care of it and sort out the details with the mfgr later.

I can't speak for Dynon in this instance, only my position. Perhaps there are more than I realize and like you said we may see more, but at the moment I haven't seen many. I guess time will tell.

Ahhh, the joys of owning an airplane!

Cheers,
Stein

PS, the KS probes are darned good - just so happens I fly behind a set myself.
 
SteinAir said:
Did you buy your Dynon from me? If so, we'll take care of it and sort out the details with the mfgr later.
Click to expand...

I did give you a fair amount of business during my build, Stein, but unfortunately the Dynon units actually came from somewhere else.
 
Today I got out and installed the new probes from KS avionics. Although the install wasn't terribly difficult in a problem-solving kind of way, the probe leads are about 4-5 inches shorter than the Dynon-supplied probe leads. Therefore, I ended up having to reroute Dynon probe harnesses which of course meant removing and re-installing of those cushion clamps! Fun times. Also, I had the solder the new connectors (smaller quick connects) that KS avionics provided to the EMS harness.

Anyway, I didn't have a chance to run the engine up (I need to do unrelated things before cowling back up) but it does appear that the probes are working and reading ambient temp properly on the EMS.

I plan to keep an eye on the new probes and will report back here when I have some time on them. Hopefully these will hold up better.

Also, I wanted to note that my distance from the flanges are closer to 4 inches once I put a ruler on them! So obviously my Dynon-supplied probes were absolutely not too close to the cylinders.
 
probe photos

Jamie:

I have 140 hours on the Dynon probes and plan an oil change right after I return from DRO. Will remove and photo at that time.

Barry
Tucson
 
We had similar symptoms on #3 EGT, and the 4 probes here:
EGT_Probes.jpg

#3 was the bent one. ~210hrs TT.

Will contact our Dynon UK agent and discuss warranties / defective parts / maybe a bad batch? Installed iaw instructions 2" below cylinder.

Have "borrowed" another set from a builder for now :)

Andy & Ellie Hill
RV-8 G-HILZ
 
Probe condition after 150 hours

After 150 hours, mine look OK (to me). I use ethanol free mogas 90% of the time & try to keep the highest EGT below 1475. Here's a sample photo.

probes.jpg


Hope this helps.
 
Dynon Probe Serial / Batch #s

In case of relevance, the probes that burnt out were labelled:
100405-000 (Dynon Part #) and G383529 0634 (Batch?)
Click to expand...
Our D-180 and Probes were supplied in ~Sept 2006.

The "borrowed" probes are G425927 0750 and seem to (all) read 20C (~30F) lower under the same conditions?

Any associated info, especially from those who also have burnt probes would be appreciated...

Andy & Ellie Hill
RV-8 G-HILZ
 
With only 50+ hours on my engine, I haven't even played around with leaning to peak yet. However, I have leaned a bit to get the fuel flow down to a reasonable flow rate. Because I apparently didn't pay attention to the instructions well enough when drilling the mounting holes in my exhaust pipes, they are not all the same distance from the exhaust flange -- within an inch, but not all the same. Plus, they're closer to the flanges than most other peoples' probes.

Consequently, my EGTs are pretty high. If I lean to around 9.5 gph at 24 squared, for example, my EGTs are all around 1400. Lean to 9.2 and a couple of them shoot up to 1425 or so. I know it's all relative, but my guess is that when I lean to peak, my temps will be really high (compared to most others).

Is there a way to remount the probes farther from the exhaust flange without having to weld the old holes closed? Has anyone successfully done it with stainless steel and clamps, for example?
 
Someone with a TIG can weld them puppies up in a few minutes.. Ask around the local machine shops.

If you know a process piping welder or a maintenance man that works in a food plant, they can do this with their eyes closed!!!
 
DavidLowy said:
I have had a similar failure on my #1 and will report when I pull the probe.
Click to expand...

My #3 EGT just went also. I pulled a probe to have a look and it looks pretty much the same as Jamie's picture above (i.e. burnt completely revealing the stubs of the two wires. )

I have 410 hours on them over about 4 years.

I called Dynon but they said they are out of stock. The replacement units are $36 each. I am thinking of replacing all 4.

Dynon said they are not eligible for warranty replacement.
 
[/QUOTE]Is there a way to remount the probes farther from the exhaust flange without having to weld the old holes closed? Has anyone successfully done it with stainless steel and clamps, for example?[/QUOTE]

Just use an extra stainless clamp to cover the hole. Ain't pretty but works fine.
 
[/QUOTE]Is there a way to remount the probes farther from the exhaust flange without having to weld the old holes closed? Has anyone successfully done it with stainless steel and clamps, for example?
Just use an extra stainless clamp to cover the hole. Ain't pretty but works fine.[/QUOTE]

Cut most all the threads off a flat-head stainless steel screw and place it in the hole. Then put the clamp over it.
 
Brantel said:
Someone with a TIG can weld them puppies up in a few minutes.. Ask around the local machine shops.

If you know a process piping welder or a maintenance man that works in a food plant, they can do this with their eyes closed!!!
Click to expand...

I've welded a few stainless exhausts and its a little more difficult than it sounds. First off the pipes have to be clean, I mean surgically clean, to start with. That means scrubbing the carbon and lead deposits off of the inside. Then you take a scrap piece of copper and back the hole up. 347 rod wont stick to the copper. Then you tape off the ends of the pipes and purge the insides with argon. To close up four holes it would take about an hour and a half and most of that is prep time.
 
rocketbob said:
I've welded a few stainless exhausts and its a little more difficult than it sounds. First off the pipes have to be clean, I mean surgically clean, to start with. That means scrubbing the carbon and lead deposits off of the inside. Then you take a scrap piece of copper and back the hole up. 347 rod wont stick to the copper. Then you tape off the ends of the pipes and purge the insides with argon. To close up four holes it would take about an hour and a half and most of that is prep time.
Click to expand...

Thanks, RocketBob -- but I think I like the sounds of Mel's idea better. ;)

Seriously, to fill the hole with a SS screw and cover with a clamp -- or even to clamp a piece of SS over the hole and mount the probes farther from the flange -- seems reasonable. It would do two things: Lower my EGTs to more reasonable readings and prevent the probes from premature destruction.

Any downside that anyone can think of?

BTW, Bob ... LOVE the 'fro. :D :D :D
 
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N8RV said:
Seriously, to fill the hole with a SS screw and cover with a clamp seems reasonable. It would do two things: Lower my EGTs to more reasonable readings and prevent the probes from premature destruction.
Click to expand...

I did this to mine when I installed the EI engine analyzer several years ago and it hasn't shown any signs of leakage.
I cut almost all the threads off the screw so it doesn't stick into the exhaust flow.
 
EGT Prob Failure

Stein,

I know this is an old thread but last night I lost #1 Prob exactly as others. My EGT's are rarely in the 1400's. I pulled all 4 and the other 3 are just about ready to fail. I purchase all my equipment from you back in 2005 and only have been flying for 2 years with 350 hrs on the engine. Would the prob's be covered by you or am I out of luck and on my own?

Let me know,

Thanks
 
I am almost in the same situation. The ceramic (???) is almost all gone on 3 of my Dynon EGT probes. I run my engine rich of peak and also rarely have them indicate more than 1400 deg F. I keep my plane in a hanger near the Gulf Coast. Just guessing but maybe this has to do more with corrosion or vibration than temperature.
 
Thinking out loud....

Just for my personal knowledge, how far away from the flange are your EGT probes? I drilled mine at 2".

I have 220 hours on my Dynon probes. I run 1450 egt usually, & no wear detected.

But I also run ethanol free mogas so I'm wondering if that plays a role in their life span?

Thanks for the info.
 
KS or EI probes?

I've been waiting to see how long mine would last. 170 hours and 2 1/2 years and the first one (#3) went yesterday.
Think I'll try the KS ones $75 each. The EI ones sound good but expensive at $94 each, are they worth the extra??
Mine where normally run indicating 1450 and never over 1500

Peter
 
Just as another data point, I just completed my annual...pulled the KS probes and they are still pristine after 180 hours.
 
Prob distance

Mine are 2 3/4" from the flange. There must have been a material deffect around that time since nothing else seems to be the cause.
 
Mine are exactly 2" from the flange. The only installation variables I can think of are the distance from the flange and the hole size. I am pretty sure both are right.

I just ordered new ones of different brand (Falcon) from Spruce. My Dynon probes lasted 230 hours.
 
I've only got about 30 hours on mine and my #3 EGT probe failed also. Dynon immediately replaced and everything working fine. Interesting that there are several folks mentioning a # 3 EGT probe failure. Can't even guess what the correlation might be.
 
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