From my experience when an engine thru bolt fails, it’s typically caused by one of two things: Under torque or over torque.
Ask Paul: Troubleshooting engine problems requires specific information
Anytime you are asking a question regarding a Lycoming engine, it’s much easier for me to respond if I have a specific engine model and serial number. Any maintenance history on the engine is also helpful, especially when troubleshooting a condition that has recently changed in the operation of the engine. I will never fault anyone for providing too much information.
Ask Paul: What’s behind the high oil temperature in my Mooney?
Question for Paul McBride, the General Aviation News engines expert: I have developed a high oil temperature issue in my Mooney. I have thrown time and money at this with a mechanic and so far can’t seem to make improvements.
What should I do with an engine that’s making metal?
Our engines expert helps troubleshoot a Piper Pacer’s engine, which just starting making metal.
What’s the harm in turning the prop by hand?
Why does our engines expert advise aircraft owners not to turn the prop by hand?
What’s the problem with my #4 cylinder?
When it comes to older aircraft, anything is possible so, as you can imagine, it also makes troubleshooting more difficult.
Is it worth it to upgrade this Cessna 177’s engine?
Question for Paul McBride, the General Aviation News engines expert: Good day Paul, we are looking at a Cessna 177 with a 150 hp engine. Wish it was a 180 hp, but the plane only has 988 total hours.
Ask Paul: Can I convert my narrow deck engine to a fuel injected engine?
The basic answer is yes, but converting an O-320-B3B engine to fuel injection may be a bigger mountain to climb than you’re up for.
Ask Paul: How can I improve my engine’s cruise oil pressure?
During my second test flight, I noticed cruise oil pressure at 55 PSI. As it has the longer housing regulator, I added three washers and replaced the check ball. The result was oil pressure at cruise around 65 PSI and 40 PSI at idle. It’s within spec, but I’d like some more room over minimums.