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Reflex

Well Known Member
This evening, I misread my torque wrench and torqued an Antisplat engine heater to almost double what it should be on my IO-390 There are no stripped threads, no bad "feel", and all appears to be OK. Incidentally, it's 1/2" NPT.

My question is, what should I do about this? Should I replace the heater, remove and re torque properly, or something else? This can't possibly be OK as I believe that as the unit heats up it will expand.

Thoughts?
 
You could get an NDT inspection to determine if there is something not good. NPT Pipe threads taper. The taper is 1⁄16 inch per inch of threading. So the additional torque applies expansive force Into the material it is threaded into. The biggest issue would obviously be if it is cracked.
 
What torque value, what lubrication (sealant), how many turns past finger tight? IMO up to two turns is OK, maybe three but that scares me.

You could remove, inspect sump for cracks with loupe or cellphone camera, re-install 1 to 1-1/2 turns past finger tight.

Lycoming SSP-1776 says 1/2-14 NPT 160 - 176 in lbs.

Heater will expand but so will the sump it is intimate with, both aluminum.
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I would remove the paint around the hole and apply liquid penetrant.
If no cracks are found, apply new paint. Install the heater.

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Good luck
 
Just a follow-up. While I can't be sure, I believe my worry was all for not...

I figured the first thing I needed to do was to remove the heater. My concern was that the threads could be to the point that it would twist apart when trying to get it out. To my relief, after about a 1/2 - 3/4 turn the heater came out very easily. So easily in fact that I feared it had broken off inside the sump. However, the entire unit came out intact.

After thoroughly cleaning up the dope, inspection of the threads on both the heater and the sump revealed no issues. I also had three folks that work with this type of fitting in sensitive applications also inspect the sump and found no issues. I Again doped the heater and installed it. This time making sure the torque was proper. The heater tightened up and "felt" very normal for 160 in/lbs.

I have a CDI torque wrench with a dial on it. Ultimately, I believe that I must have bumped the lazy arm on something during my original installation.
 
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