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Damaged thread at engine case oil return fitting

lndwarrior

Well Known Member
Engine is an O-235. I finally traced an oil leak to a damaged thread inside the case at the oil return fitting.

Is the best solution to run a tap down the thread? If so, any tips on doing this? Since it's inside the engine case I'm concerned about screwing this up.

Any suggestions you have would be appreciated.

TIA
Gary
 
Running a tap to clean the threads is what I would do. Do it slowly and coat the tap with copious amount of grease to catch any metal filings. Go in a couple of turns remove, clean the grease off. recoat, and go in again. Wrap the male threads liberally with teflon tape and tighten. If it will not tighten, the only alternative I know of is helicoil. Get your local mechanic to do the job. Good luck, Dan from Reno
 
heli-coil for an NPT thread designed to seal?? Maybe this recommendation should be reconsidered.

Minute - - -sorry

My case had one helicoil installed by crankcase services in a boogered oil return hole at overhaul. A little thread sealant and it is fine. NPT threads don?t seal without some sealant.
 
My case had one helicoil installed by crankcase services in a boogered oil return hole at overhaul. A little thread sealant and it is fine. NPT threads don?t seal without some sealant.

Good to hear. I deleted my post then a little research turned up some claims but "with sealant" was not very definitive. Your first hand knowledge is reassuring.
 
Wrap the male threads liberally with teflon tape and tighten.

Teflon tape? Really? Maybe if you are super super experienced in its application.

Otherwise, Locktite 567 is bullet proof and idiot proof....and personally, I resemble that remark.....
 
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