Spent 2 years using the wrong torque wrench setting on cylinder heads

I had this 1980s Cessna 172 and kept getting weird compression readings after top overhauls. Turned out I was using the torque spec from a manual for a different engine model the whole time. A senior mechanic noticed my readings were off by about 15 ft-lbs and pulled the old manual out. Felt pretty dumb when I saw the right number was way lower than what I had been doing. Anyone else ever mix up specs from different service bulletins?

2 comments

2 Comments

uma_baker881mo agoMost Upvoted

That coffee spill story reminds me of a time I saw a guy at a regional airline who was using the wrong torque on spark plugs because his service bulletin binder had pages stuck together from a soda spill, so he was reading the values for the oil filter adapter instead. He had been putting 50 ft-lbs on plugs that were supposed to be at 30, and they were cracking in the heads like crazy, causing all sorts of oil leaks and misfires. It took them like three months and a whole engine teardown to figure out the real cause, and he felt pretty stupid when the supervisor just flipped the pages to the right spec. Now they laminate all the critical pages in their shop manuals, which seems like a cheap fix for a problem that can cost you a whole weekend and a lot of money.

cole_hall1mo ago

I had a buddy who torqued his landing gear bolts on a Piper Cherokee to the spec for the flap brackets once. He couldn't figure out why the gear felt stiff until we found the manual pages were glued together from an old coffee spill. Ended up stripping two bolts and had to drill them out on the hangar floor. Ever have a bad manual or cross-reference chart cause you a headache like that?