Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Dynon EGT probe failure (x4)
- Thread starter Jamie
- Start date
N8RV
Well Known Member
Update: After completing my condition inspection over the weekend, I went flying and noted that my #3 EGT was suddenly spiking to over 1500* and then down to 13XX* ... then back over 1500* ... and back down.
Of course, I didn't bother to pull the probes when I had my cowling off, but now I intend to. My initial thought is that it's just a bad connection, and replacing the connector will solve the problem. However, after reviewing this thread, I'll be very surprised if my probe isn't burned to a crisp! Yeah, it's #3.
I'm planning to pull them later this week and see what I find. Stay tuned ...
Of course, I didn't bother to pull the probes when I had my cowling off, but now I intend to. My initial thought is that it's just a bad connection, and replacing the connector will solve the problem. However, after reviewing this thread, I'll be very surprised if my probe isn't burned to a crisp! Yeah, it's #3.
I'm planning to pull them later this week and see what I find. Stay tuned ...
Scott Hersha
Well Known Member
Jamie,
My Dynon supplied probe on cylinder #1 indicated the same as yours did, and it happened a few times now, but then returns to normal operation. I pulled the probe out for a look when it happened the first time and the probe looks fine. It's solid and all there. I'll check my other ones today for comparison. That particular probe may be getting ready to come apart, so I'll see. That particular cylinder is my coolest (EGT) and the warmest (CHT). The highest I've seen on that cylinder is about 1320. My probes are mounted 2" down from the cylinder and I have 200 hours on them. When they go for good, I'll get those better quality ones made from inconel.
My Dynon supplied probe on cylinder #1 indicated the same as yours did, and it happened a few times now, but then returns to normal operation. I pulled the probe out for a look when it happened the first time and the probe looks fine. It's solid and all there. I'll check my other ones today for comparison. That particular probe may be getting ready to come apart, so I'll see. That particular cylinder is my coolest (EGT) and the warmest (CHT). The highest I've seen on that cylinder is about 1320. My probes are mounted 2" down from the cylinder and I have 200 hours on them. When they go for good, I'll get those better quality ones made from inconel.
N8RV
Well Known Member
Went to the hangar last night and pulled the cowling. Here's a shot of the #3 probe in place that has been giving bad info ...
I measured the placement of all four probes before doing anything else. The distance from the exhaust flange ranged from 1.25" to 1.6". Apparently, I only read the instructions where it said to place them on straight pipe not curves, and to be careful about getting the spark plugs out, totally ignoring the part about placing them THE SAME DISTANCE FROM THE FLANGES, in the 2"-8" range. Duh.
Anyway, the #3 probe was at 1.25" from the flange and I fully expected to find it burned to a crisp. However, when I pulled it out, it looked like this ...
So, following Mel's suggestion, I cut down a #6 SS screw and plugged the hole, securing it with a SS hose clamp and saftied it. Then, I remounted the EGT probe at exactly 3" ...
I then replaced the connectors, since that was apparently the source of the problem, not a deteriorated probe. I need to go flying now, to make sure that my fix indeed solved the problem, then decide whether to remount the remaining probes 3" from the flanges.
I measured the placement of all four probes before doing anything else. The distance from the exhaust flange ranged from 1.25" to 1.6". Apparently, I only read the instructions where it said to place them on straight pipe not curves, and to be careful about getting the spark plugs out, totally ignoring the part about placing them THE SAME DISTANCE FROM THE FLANGES, in the 2"-8" range. Duh.
Anyway, the #3 probe was at 1.25" from the flange and I fully expected to find it burned to a crisp. However, when I pulled it out, it looked like this ...
So, following Mel's suggestion, I cut down a #6 SS screw and plugged the hole, securing it with a SS hose clamp and saftied it. Then, I remounted the EGT probe at exactly 3" ...
I then replaced the connectors, since that was apparently the source of the problem, not a deteriorated probe. I need to go flying now, to make sure that my fix indeed solved the problem, then decide whether to remount the remaining probes 3" from the flanges.
Last edited:
N8RV
Well Known Member
Update:
After remounting the #3 EGT probe at 3" and replacing the connectors, I decided to do the same with the others. All EGT probes are now exactly 3" from the exhaust flange.
I took it up for a test hop and found that the #3 EGT reading is the coldest, but all are cooler. Seeing that there's a significant difference in readings now, I'm tempted to replace ALL connectors and see if the readings are more consistent.
The stranded wire from the probes is pretty fine, and I'll bet getting a solid crimp is darned near impossible. With the new connectors, I doubled-over the wire before crimping. Something to consider when initially installing EGT probes.
After remounting the #3 EGT probe at 3" and replacing the connectors, I decided to do the same with the others. All EGT probes are now exactly 3" from the exhaust flange.
I took it up for a test hop and found that the #3 EGT reading is the coldest, but all are cooler. Seeing that there's a significant difference in readings now, I'm tempted to replace ALL connectors and see if the readings are more consistent.
The stranded wire from the probes is pretty fine, and I'll bet getting a solid crimp is darned near impossible. With the new connectors, I doubled-over the wire before crimping. Something to consider when initially installing EGT probes.
Jamie Aust
Well Known Member
Hi Don thanks for your input, could you tell me how much cooler the temps are please. Im about to mount my probes, and hope 3 " will work for me.
N8RV
Well Known Member
Jamie, before I moved the probes the temps were running in the mid-1400* range when leaned to peak. Now, #s 1, 2 and 4 are closer to 1400* and #3 runs around 1350.
My guess is that if I replaced the connectors on the remaining probe leads, the other three readings would drop as well. Just a guess, but I can't think of any reason that only #3 is significantly cooler now since the probes are all at the same distance from the flange.
RV10inOz
Well Known Member
After seeing your photo of the probe, and reading the comments, you do not have a EGT probe or connector issue at all. Well from my reading your comments anyway.
I will bet you a few beers, the problem is spark plugs.
What I suggest you do and if you do not have an all cylinder monitor (I assume you do by the numbers posted) this gets a bit hard, run the endine at say 1200-300 rpm, and lean it aggressively, then switch to one mag, watch the EGT's, they should ALL rise together, then go back....let it all settle and do the other mag, they too should ALL rise.
Do this in flight while running LOP or as lean as you can get. It will uncover which cylinder has a crook plug. The crook plug is causing the random "rising" EGT just the same as when you do the test above, whil running with both mags the cylinder that effectively runs on one at times is the one with the rising and falling EGT.
Now pull all your plugs, have them cleaned and regapped to around 16 tho and pressure tested. Or just clean and gap them yourself. Do this every 100 hrs.
I just did mine today (after 135hrs) and the gaps were up to 20-22 thou not 15-16. Engine is back to smooth again when LOP.
Your D120/180 is your best friend when you learn to understand what it all tells you!
How old are your plugs and when were they serviced last?
DB
PS.....the actual EGT number is almost meaningless, its the trends that matter.
[email protected]
Well Known Member
suspect the connection...
hi Tony, the crimps on the sensor side have been pretty unreliable for me... the solid wire does not hold well unless it is doubled over and i have had to replace the supplied connections on three of the four probes... i used a butt splice rather than the spade connectors.
hi Tony, the crimps on the sensor side have been pretty unreliable for me... the solid wire does not hold well unless it is doubled over and i have had to replace the supplied connections on three of the four probes... i used a butt splice rather than the spade connectors.
apkp777
Well Known Member
Thanks Stephan, I suspect its the connectors. As you probably know by know, it's hard to work on the plane when there's so much flying to do. "Uh, let's see shall I go work on the plane or fly? Who needs EGT anyway!"
apkp777
Well Known Member
I poked around my connections and looked at the probe installation during an oil change and found nothing obvious. However, the next flight the probe was completely dead. A day later I received a replacement probe and again decowled and swapped probes. Op checked good.
I am wondering if anyone knows the expected out put voltage range for the probes. I would like to test the probe in boiling water. The probes looks perfect. I sort of suspect a bad connection at the spade connector, but the connection looked to be sufficient.
Thermocouples don't put out a voltage for a temperature. They put out a voltage for a difference in temp, so if you put them in boiling water you also need to know the temperature where the voltmeter attaches to the probe.
Assuming it's 75 degrees out and you're at sea level, an EGT thermocouple will generate 3.1mV (0.0031 V). You need a good voltmeter to have any accuracy at these voltages.
Thermocouples are very basic devices mechanically and just checking for continuity between the two wires with an ohmmeter will test for 99.9% of problems. They should look like dead shorts.
Assuming it's 75 degrees out and you're at sea level, an EGT thermocouple will generate 3.1mV (0.0031 V). You need a good voltmeter to have any accuracy at these voltages.
Thermocouples are very basic devices mechanically and just checking for continuity between the two wires with an ohmmeter will test for 99.9% of problems. They should look like dead shorts.
Flybuddy2
Well Known Member
Just an FYI--just had a Dynon EGT sensor probe fail (3rd one in 18 months-all different cylinders). Went to order from Dynon as I'm used to doing and found the cheapest to ship the $36 part was $29..There's a note that states that Dynon now has a $20 handling fee for all orders including small part orders. Are they having financial troubles or are they excessively inefficient on orders? What logic is there in chasing away large order customers when they make more profit on direct orders?
RV10inOz
Well Known Member
Buddy
Are you in business?
The typical invoice cost for many businesses, ( not Walmart ) is possibly like $70 so when you place an order for even $500 they are lucky to be making a profit.
If more folk actually realised what it REALLY takes to run a company, they would not think the way they do.
Do you like your purchases subsidizing others ?
Are you in business?
The typical invoice cost for many businesses, ( not Walmart ) is possibly like $70 so when you place an order for even $500 they are lucky to be making a profit.
If more folk actually realised what it REALLY takes to run a company, they would not think the way they do.
Do you like your purchases subsidizing others ?
Glas467
Well Known Member
EGT Probe Distance
I have an IO-360 with an original set of VMS probes, replaced one of them last year with just over 650 hours on it, the other 3 are still going strong now with close to 700 hours. My probes are located approx 4 inches from the face of the exhaust flange. I also routinely fly lean of peak with cruise EGTs in the ~1500F-1550F range.
In my experience, 2"-3" from the flange is too close to the exhaust flame for good probe longevity.
Reggie
I have an IO-360 with an original set of VMS probes, replaced one of them last year with just over 650 hours on it, the other 3 are still going strong now with close to 700 hours. My probes are located approx 4 inches from the face of the exhaust flange. I also routinely fly lean of peak with cruise EGTs in the ~1500F-1550F range.
In my experience, 2"-3" from the flange is too close to the exhaust flame for good probe longevity.
Reggie
shipping charge
Glad to know about new shipping cost its getting to be a big factor in building a plane Ive always thought that I would install Dynon and Im ready to order next week now Ill also take a look at other options.I like companys that stand behind there products .
Glad to know about new shipping cost its getting to be a big factor in building a plane Ive always thought that I would install Dynon and Im ready to order next week now Ill also take a look at other options.I like companys that stand behind there products .
I've left many a web page order form when I get to the payment page that has excessive shipping/handling charges. Some times it pays to shop around and and compare the total costs. I keep a running list in the shop for all the little items I need but can put off until absolutely necessary so hopefully I can combine what would have been separate orders into one. I sell on ebay and ship every day. I add a $2 handling charge to my actual shipping costs to offset the packaging materials cost (peanuts, boxes, tape, and fuel) which I consider to be fair. My guess is that Dynon really would rather you deal with their distributors/dealers.
Hi Guys
I just had #4 EGT probe fail after 76 hours, it too was a Dynon supplied probe with the same symptoms as others have described.
I have ordered a replacement, but would like to establish if its a connector or probe failure, if connector then I guess have a spare probe.
What resistance are people seeing when they measure a good probe ?
Cheers
Eddie
I just had #4 EGT probe fail after 76 hours, it too was a Dynon supplied probe with the same symptoms as others have described.
I have ordered a replacement, but would like to establish if its a connector or probe failure, if connector then I guess have a spare probe.
What resistance are people seeing when they measure a good probe ?
Cheers
Eddie
Last edited:
After checking my faulty probe today, I discovered that the supplied female spade connector was loose on the EGT probe cable, I re-crimped both connections and all is back to normal.
Found this by inserting the multi meter probes and jiggling the wiring, the caused the meter reading to drop in and out.
Cheers
Found this by inserting the multi meter probes and jiggling the wiring, the caused the meter reading to drop in and out.
Cheers
miyu1975
Well Known Member
Another dynon EGT probe failure to report. On my trip to Texas last weekend my number 3 EGT started going crazy with erratic changes. All CHTs and other engine gauges in the green, so I kept on going figuring I had a probe issue. Yesterday I pulled the probe and plugged in number 1 to 3 probe, thus determining what I already pretty much knew.. Before that I recrimped the connectors hoping maybe that would fix it...it did not.
I called Dynon and was told the the EGT probes they sell or of the "economical" kind and I should expect them to bad from time to time. Did mention I have 70hrs on these probes.
I am going to replace all the egt probes with ksavionics probes recommended by rocketbob. A little more expensive, but hopefully I will get more than 70 hours out of them.
I called Dynon and was told the the EGT probes they sell or of the "economical" kind and I should expect them to bad from time to time. Did mention I have 70hrs on these probes.
I am going to replace all the egt probes with ksavionics probes recommended by rocketbob. A little more expensive, but hopefully I will get more than 70 hours out of them.
[email protected]
Well Known Member
'failure' is more likely connection...
These are just two wire thermocouples with the tips protected for exposure to high temperature... probe failure is far less likely than connection failure. The wire used for these thermocouples is too small to make a quality vibration resistant connection. Both of the J and K type used are itty bitty wire but further frustrating the connection issue for the EGT wire is the challenge of getting a good connection to a single wire strand... at least the CHT wire has a few strands.
What we really need are probes with thicker stranded wire to support a quality crimped connection that resists vibration better. The current ones work fine if you can keep the connection vibration and movement free and make sure that the crimp is good (fold the single wire back on itself).
These are just two wire thermocouples with the tips protected for exposure to high temperature... probe failure is far less likely than connection failure. The wire used for these thermocouples is too small to make a quality vibration resistant connection. Both of the J and K type used are itty bitty wire but further frustrating the connection issue for the EGT wire is the challenge of getting a good connection to a single wire strand... at least the CHT wire has a few strands.
What we really need are probes with thicker stranded wire to support a quality crimped connection that resists vibration better. The current ones work fine if you can keep the connection vibration and movement free and make sure that the crimp is good (fold the single wire back on itself).
To add to this, i have folded the wire back onto itself onto the insulated portion of wire. You really get a nice thick body to crimp onto.
I have not had any issues with my factory probes so far. Factory crimps have held up fine. I did have early problems with the blade connection itself going flakey. The hot and cold cycle would loose the male and female blade connectors themselves. To solve that, i bent the male blade slightly to create some spring tension. I then put heat shrink over the whole thing.
Thus far, I have 230 hours on mine so far without a glitch.
I have not had any issues with my factory probes so far. Factory crimps have held up fine. I did have early problems with the blade connection itself going flakey. The hot and cold cycle would loose the male and female blade connectors themselves. To solve that, i bent the male blade slightly to create some spring tension. I then put heat shrink over the whole thing.
Thus far, I have 230 hours on mine so far without a glitch.
Last edited:
Smoke Master
Member
The answer to your problem is a company called Omega Engineering. They make probes of all kinds and have most in stock. They will also make custom probes at a very reasonalbe price. I've used the K-type probes for 35 years and they are good to at least 2200F. I would suggest you use an inconel sheath and spec the largest wire guage that will fit the ID of the probe you need. If Omega can't solve the problem it can't be fixed.
jjconstant
Well Known Member
not just Dynon
I just had a GRT supplied probe on #4 fail (burnt) at 250hrs. Fortunately, both Mattituck AND GRT supplied EGT probes so I had 4 spares. I had already given one to a friend with another GRT probe that failed, so I asked my friend Bruce, who was a partner in KS engineering whether I should use his probes and his response was "well, 250 hrs on those probes isn't unusual, just go through your existing stock and if you need one of ours when you run out we'll do it then."
I drilled my exhaust where the instructions suggested; somewhere between 2 and 3 inches IIRC. For what it's worth, when up high I run at peak, which in reality is 2 cylinders very slightly rich and 2 very slightly lean. This is up above 11,500ft where I'm definitely below 75% power. Down lower I run LOP and yes, I've balanced the injectors.
Have those folks who have had burnt probes and moved them further down the pipes shown any extra longevity?
I just had a GRT supplied probe on #4 fail (burnt) at 250hrs. Fortunately, both Mattituck AND GRT supplied EGT probes so I had 4 spares. I had already given one to a friend with another GRT probe that failed, so I asked my friend Bruce, who was a partner in KS engineering whether I should use his probes and his response was "well, 250 hrs on those probes isn't unusual, just go through your existing stock and if you need one of ours when you run out we'll do it then."
I drilled my exhaust where the instructions suggested; somewhere between 2 and 3 inches IIRC. For what it's worth, when up high I run at peak, which in reality is 2 cylinders very slightly rich and 2 very slightly lean. This is up above 11,500ft where I'm definitely below 75% power. Down lower I run LOP and yes, I've balanced the injectors.
Have those folks who have had burnt probes and moved them further down the pipes shown any extra longevity?
