Bent push rod?

T

t-cart

Active Member
I've got a question for you mechanic types.

I've just started flying an Aztec with IO-540's. Developed a pretty substantial oil leak on the left and found a cracked tube. Pulled the rod and it was bent. What are the possible causes of this? The mechanic said back fire was a possibility. The engine had no vibration, missing, popping or anything un-normal prior to this that I am aware of.

I'm new with this particular engine and want to know if I did or am doing something wrong. Takeoff at full power then back to 25 square and then to 23-2400rpm. I don't get over 400 feet agl with this airplane, does this make a difference in the book power settings?

I've asked the owner about retrofitting a couple of PT-6's, but it's not in the budget. :)
 
I can't think of anything other than a backfire short of a catastrophic timing problem. I've only dealt with bent automotive pushrods due to things like mechanical overrevs (downshifting way too early), riding the rev limit fuel cutoff, or a timing chain breaking. Just going out on a limb, have you ever known the engine to over-speed?
 
OhioStatePilot said:
I can't think of anything other than a backfire short of a catastrophic timing problem. I've only dealt with bent automotive pushrods due to things like mechanical overrevs (downshifting way too early), riding the rev limit fuel cutoff, or a timing chain breaking. Just going out on a limb, have you ever known the engine to over-speed?
Click to expand...

No, I really know very litle about the engine other than when I started flying it a few weeks ago. The engine in question has 950 hrs SMOH.

Thanks for the reply!
 
No worries, but I can see why you're asking... it's very odd. Pushrods don't just bend out of the blue. At least I've never heard of that happening. As far as when it happened, it might have happened all at once when it started leaking, or I'd think it possible that it could have happened awhile ago and continued to run just fine with a minor bend. That would have weakened the pushrod and it wouldn't necessarily have taken a major force to finish the job.

I'd really like to hear if anyone else has some other idea on what might have happened.
 
Bent pushrods are nearly always the result of a stuck valve. Valves generally stick when a piece of carbon or other debris gets stuck in the valve guide, sometimes they take care of themselves, other times they stick hard and you have to pull the cylinder to repair them.

It probably has nothing to do with how you are operating the airplane, so no worries there.
 
trafficinsight said:
Bent pushrods are nearly always the result of a stuck valve. Valves generally stick when a piece of carbon or other debris gets stuck in the valve guide, sometimes they take care of themselves, other times they stick hard and you have to pull the cylinder to repair them.

It probably has nothing to do with how you are operating the airplane, so no worries there.
Click to expand...
:yeahthat:
 
You must log in or register to reply here.
Back
Top