New EGT Probe Time

Approximately 630 hours

At approximately 630 hours, I had my first EGT probe failure.  It of course causes no operational problems, but makes you do a doubletake and look for engine problems when it happens.  I didn't know what to expect for a lifetime on the probes, as I've never had an engine for this many hours before, but after talking to a couple of companies that sell probes, it sounds like these types of 1/8" probes can of course have a varied lifetime.  Average may be something in the area of 1000hrs.  600 would be low-average, and 2000 would be pretty high.  I don't know that other method than experience with a certain brand though can give you a real average, as it does matter what type of conditions you put on the probe.  I run LOP often, in cruise.  That could be better, or could be worse on the probes.  That means I'm peaking between 1400 and 1425 usually, and running in the mid or high 1300's for long periods of times (my average flight leg is maybe 4 hours).  Operating ROP may be easier on probes, or harder...I guess it depends on what the peak temp is, among other things.

So when I replaced the bad one, I happened to have a spare on hand.  Mine were Grand Rapids Tech (GRT) probes, and I had the inexpensive, standard probes, that have black heatshrink on the upper end.  I didn't even know other probes were available, but coincidentally there were forum discussions on the Matronics RV-10 list about probes, and I found out that for $9 more, GRT offers "Hastelloy" type probes.  The same size, and everything but supposedly these are more durable.  They have white heatshrink on the ends.

After trying a hastelloy probe (I think I tried 2 of them) I decided to replace them all proactively, and got 7 new ones.  Out of the 7, one was reading about 50 degrees different than the others, so I sent that back.  Not sure why a probe would read incorrectly, but the new one worked well.  After inspecting the other probes, I found that I had others that were on the verge of failure.  Some probably could have gone any day, some maybe would have 50 more hours in them.

See the pictures below...the first pic is 3 probes.  The one on the Left is the standard probe (new), the middle is the hastelloy probe (new), and the one on the right is my bad probe.  The second pic is a close-up of the 3, and the 3rd is a close-up of the failed probe.  4th and 5th are close-ups of the others. 7 and 8 are views of another probe, showing the bulbous head on the end, where the probe shaft was wearing away.

RV20100613125327.jpg RV20100613125335.jpg RV20100613125345.jpg RV20100613125350.jpg
RV20100613125355.jpg RV20100613125407.jpg RV20100613125923.jpg RV20100613125945.jpg

Replacing the probes is very easy, and I did find that supposedly E.I. (Electronics International) has a great quality probe (for nearly double the price), but one thing to remember is that you have to wire them in again.  GRT probes have about a 2' lead on them.  EI probes I think were 12 or 16".  So, if I had switched to EI probes I would have had to order custom lengths, or add jumpers, and either way would add cost, and jumpers add one more failure point.  So, I stuck with GRT and bought their good hastelloy probes.  I don't know if you can go "wrong" no matter how you do it, but, if I were installing GRT probes again for a new install, I'd leave a service loop or slack so that I could go with shorter probes some day if necessary.  If the GRT hastelloy probes go 1000 hours though, I'll be plenty satisfied.  The cost isn't astronomical.

Site Home  |  N104CD Home