fun with cylinders

There I was, enjoying the day when Joe Pilot, Fly-boy extraordinaire, shows up with the following problem in his aerial transport (I quote this exactly the way it was written): There is a viberation that seems to be come from the engine.

So I track down the stick actuator in question and try to pin him down on some small minor issues with this.  Things like was it shaking on the ground or in the air?   Was the magneto drop check OK?  Any change in vibe with changes in power settings?  Those kind of things.   Anyway, I jump in the machine and drive it out to the end of the ramp to run the snot out of it.  Naturally, I can’t really feel anything untoward and any vibration is probably coming from the whole thing shaking simply because I have it at max.  Back to the ramp I go…

The engine section of the maintenance manual isn’t all that strong in the troubleshooting department so I give it a perfunctory glance to see if the word “viberation” shows up.  No surprise there.  Out comes the compression tester and the magneto timer.  By this time the engines good and hot and I can’t pull the spark plugs without catching the exhaust pipes at couple dozen times. The air’s still a bit blue…

Five out of the six cylinders are just peachy.  The bad one is, naturally, the middle cylinder in the left bank of three.  Probably the  hardest one to change.  I grab a whole new assembly; cylinder, piston, rings, valves, all the gaskets, and my trusty rusties, and sally forth to take this motor down to individual molecules.

The cylinder’s held on with eight nuts.  That’s it.   However, to get to those eight little threaded beauties, one must first wend their way through the entire exhaust system, two of three intake tubes, all the cooling baffles that direct air over the cylinders to keep things from melting down, half the heat system, the fuel injector lines, the spark plug harness, and a few dozen wire harness clamps some sadist engineer decided to put in for fun.  I get to pull the valve pushrods and rockers, their protective tubes, and the hydraulic lifters that make ’em work.  Takes about an hour and a half to get everything down to where I’m ready to yard the offending unit off the crankcase.  I get the cylinder off and sure enough the rings have been sticking a bit.  There are scratches on the cylinder wall and the piston’s a bit scored too.  Out comes the hammer and with a few tippy-taps, the piston comes off. 

Now for the fun part.  As most general aviation manuals read, installation is the reverse of removal  providing  the mechanic kept all the parts in some semblance of order.  I’m that guy.  (I know, Heltch. you’d never believe that from my high school days.)  Couple hours, a few skinned knuckles, several trips to the parts room across the hangar for replacement hardware, and badda-boom, badda-bing, one installed cylinder, complete with all the extras. 

The run up and leak checks were just fine and the bugmasher’s back up front ready to go again.  Long day out in the sun and the smoke, but these are the fun days.  Beats sitting at a desk any day….


1 Response to “fun with cylinders”

  1. 1 Da Goddess August 5, 2010 at 12:39 am

    “Viberation”…must remember that. In fact, I think I need to start a whole new blog and call it something created wholly of typos. Viberation Natoin, perhaps.

    Keep your O2 clean and yer powder dry, P2

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