If you have an IO 550 - please read - oil temp probe failure!

[tomn]

Its been a little while since I've posted but I wanted to pass along some critical information that might help prevent an engine failure.  I have not read anything about this here so sorry if it is old information to some.

 

I've been reading quite a lot after purchasing my Bonanza (no comments please - still missing my Mooney) and ran across an article from 2006.  The pilot, who is actually based at my home airport, had an in-flight engine failure because of a broken oil temperature probe that was installed improperly when an engine monitor was added to his plane.  His plane had an IO550 and the oil temp probe was installed just above the vernatherm in the oil cooler housing.  It was installed in a port using reduction bushing to take the 3/8 NPT hole down to 1/4 NPT to fit the probe.  The probe was installed deep enough in the port to be hit by the vernatherm each time it opened.  It eventually broke the probe in two and all the oil was pumped out through the wire passage hole.  The result was a seized motor - luckily he was able to dead stick it into an abandoned private strip and walked away with nothing more than a hole in his motor where the rod had come through.  

 

After reading this, I quickly checked mine expecting it to be fine since the motor had been replaced about 90 hrs before I bought it. The JPI had been installed years earlier.  I was surprised to find that the probe was installed in the same location as his.  We removed the probe and found a deep nick in the tip and a slight "V" bend in the barrel.  There is a crease midway down the length of the probe barrel that is 180 degrees opposite the nick. The vernatherm was obviously pushing it pretty hard - enough to actually bend it against the inside bore of the reduction bushing.  

 

There is a 1/4 NPT plug in the front left of the motor just behind the prop that is a much better location for the probe.  Mine is in the process of being relocated there with the oil cooler port now plugged and safety wired.

 

Here are two pictures of his broken probe, one showing the damage to mine, and one showing where it was installed on my engine before it was removed.

 

If you have an O with an engine monitor installed and have not heard about this, check to see that the oil temp probe is not installed like the one in the picture on my engine - NOW!  Both the IO520 and IO550 have this same configuration so pass this along to anyone else you might know with either of these motors with an engine monitor installed.  

 

Tom

[Marauder]

The name sounds familiar, Tom, right? Plane just doesn't sound familiar Give us a PIREP on the Bonanza. Love to hear how much more you are spending on fuel, maintenance, parts, etc. Seriously, let us know how it working out. BTW -- the part you made for me "fabulous". It's red now! Sent from my iPad using Tapatalk

[Seth]

Thank you.   Will check next time I'm at the hanger.

 

-Seth

[tomn]

Chris, the plane is working out great so far although I do miss the Mooney - find myself looking at them where ever I go...  I only have about 20 hours on it so far so I don't have much history with it yet.  I just got back from Allentown PA today - flew over your neck of the woods with ATC giving me the scenic tour of the bay due to storms west of DC and Baltimore.  I am still playing with it but it looks like I can cruise 10K ft in the 170kt range burning about 13 gph at peak.  Faster with more fuel if I want to, at little less speed and around 11.5 to 12 gph LOP but I have not played with that much.  

 

This oil temp probe issue is not good.  The failure of mine was eminent - most likely sooner than later due to the bend in the probe and the depth on the nick in the end.  I can't stress enough that anyone with a IO550 with aftermarket monitor installed check the location of the oil temp probe.   

 

Fly Safe,  Tom

 

Glad the knob has worked out and is now red!

[M016576]

Thank you. Will check next time I'm at the hanger.

-Seth

Mine isn't located there (checked today). I'm interested to know if all 550-A's have the sensor located elsewhere, or if it's a case by case basis kind of thing.

[tomn]

This was an oil temperature probe for a JPI engine monitor - not the factory probe.  You only need to check if you have a JPI or other monitor installed with its own oil temp readout.  Look at the bottom of the oil cooler where the vernatherm is located.  If you are not familiar with that, just look at the bottom of the oil cooler (behind last cylinder on pilots side) and see if you have a probe with wires coming from it - if it looks like this picture investigate further. Let me know if you have any questions, I can give anyone more details.  

 

Tom

[M016576]

This was an oil temperature probe for a JPI engine monitor - not the factory probe. You only need to check if you have a JPI or other monitor installed with its own oil temp readout. Look at the bottom of the oil cooler where the vernatherm is located. If you are not familiar with that, just look at the bottom of the oil cooler (behind last cylinder on pilots side) and see if you have a probe with wires coming from it - if it looks like this picture investigate further. Let me know if you have any questions, I can give anyone more details.

Tom

Looked again today . I have an EI CGR--30P installed. There is a hose and oil press transducer coming from there.

For reference:

Mooney M20J Missile w/ IO-550A