Bent push rod, a birds nest and now missing fuel

[k9medic]

Some strange things going on lately with my plane. Cherokee 6/260

Got to the plane on Friday and loaded it up to head out on a trip that was to be around 2.4 hours.

Checked the fuel in the plane and found that the left wing tip tank was completely empty. I thought that was odd but figured maybe the refueler missed that tank on the flight a week earlier (flew 4.2 hours that week.) Called for fuel and didn't think twice about it.

On approach into the airport, I pulled the power back to initial a descent and the engine stumbled just a bit. I figured I maybe leaned it a little too much so I enriched the mixture and the stumble went away.

Fast forward to today - I arrived at the airport and started my preflight. Found the left wingtig tip tank again empty! No fuel drained on the ground to speak of but the right main tank was now REALLY full!

I continued the preflight and saw some grass in the air intake. As I reached my hand in there, I found more grass so I pulled the cowling off and found a whole darn bird's nest between the #4 & #6 cylinder!

While cleaning the grass out of the cowling I happened to notice that one of the push rods on the #2 cylinder was bent! Now I know what the stumble was. Darn stuck valve.

Some thoughts here for the group:

• The fuel draining from the tip tank into a main tank seems to correspond with the fuel selector. Whatever tank the selector is set to, it seems to drain into.
• Why would I stick a valve when reducing power? It was flying great at 4500' for 2.3 hours. Fuel flow was leaned to 14.5 gph and power setting was set for 75% since we have a new %1 cylinder.
• Any chance that running straight mineral oil would cause the stuck valve? The oil has 8 hours on it.
• Good thing for a solid preflight for the bird's nest. We landed round 1930 Friday night and so the nest had be built in 2 days.

Now to find a mechanic in the Jefferson, GA area that can take a look at this thing...

 

[MauleSkinner]

Good thing for a solid preflight for the bird's nest. We landed round 1930 Friday night and so the nest had be built in 2 days.

I’ve seen them built in an afternoon. I’ve seen a good start over lunch. Birds are pretty industrious this time of year.

 

[k9medic]

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[PaulS]

That sucks, I doubt the valve is anything you did, just bad luck pretty much. The only comment I have about the fuel is eyeball each tank before you start up, every time. That's what I do, maybe you do too, but you didn't mention it. Nothing a bunch of cash can't fix.

 

[k9medic]

We typically fly with full fuel so it is common for us to verify what we have.


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[Lindberg]

I continued the preflight and saw some grass in the air intake. As I reached my hand in there, I found more grass so I pulled the cowling off and found a whole darn bird's nest between the #4 & #6 cylinder!

Is opening the cowl not a part of your normal preflight?

 

[Skip Miller]

On all PA-32s that I have seen, you don’t open the cowling, you remove it. Two person job.

-Skip

 

[k9medic]

On all PA-32s that I have seen, you don’t open the cowling, you remove it. Two person job.

-Skip

Correct. Big upper cowling that does not get removed as part of preflight.


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[RyanB]

Any prior symptoms of a sticking valve before this discovery?

 

[k9medic]

None and that makes zero sense.

No shaking during start up. No rough running.


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[PaulS]

We typically fly with full fuel so it is common for us to verify what we have.


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I just looked at your ratings in your sig, you've been around the block, lol. The only other suggestions I have is cowl plugs if you don't have them. Birds suck, but good thing you caught it. Let us know what happens with the engine.

I started a pretty new sr 20 ( about 400 hours on the engine) a while back and it sounded like someone smacking the engine with a ball peen hammer for about a minute, then the noise stopped and it ran fine, it was a training mission. We shut it down, looked for holes, nothing was amiss. Talked to the mechanic, he said do a full power run up, if it ran ok it should be ok. The airplane was going in for it's 100 hour the next day. So we did the run up, it was fine, we flew. The airplane goes in, turns out a valve was burnt and must have begun sticking, which caused the noise. The plane had 3 jugs replaced. You just never know.

 

[MajorTurbulence]

I’ve seen them built in an afternoon. I’ve seen a good start over lunch. Birds are pretty industrious this time of year.

Yes, startling but true. Happened to me in Michigan after landing and departing the next day. It was one hell of a mess in the cowl.

In springtime, I always check for any remnant of twigs or dried grass in the lower rear engine opening and, even though I have cowl plugs in place, carefully look through the oil dipstick door which is difficult in bright sunlight. Anytime I see anything suspicious. I remove the upper cowl (Pa28) by myself, although I suspect the bigger Pa32 cowl may be too difficult alone.

 

[Lindberg]

Correct. Big upper cowling that does not get removed as part of preflight.


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Interesting. Is there another way to inspect the engine? On all the little birds I fly, it's not too difficult to peek inside, so I do. And I've been told it's overkill, but after reading your story, I will continue to do it. I wonder how you would have discovered the bent pushrod if not for the bird nest? Maybe someone was looking out for you.

 

[Velocity173]

I had a bent a pushrod running straight mineral oil. It was just after the break in period. Overhaul shop fixed the stuck valve free of charge and said there was a tiny bit of corrosion on it. Guess it’s important to fly it regularly just after break in period.

 

[k9medic]

Yep, been flying for a while both personally and professionally. First time I have EVER seen this happen on an aircraft that is normally inside. Aircraft is in a hangar when at home so I know it didn't happen there.

I do believe things happen for a reason. I also believe in doing a good preflight so I take time to look into all the little spots. One of the aircraft I fly for work only gets a look under the cowling every 10 flight hours or 14 days - and that is by a mechanic.

I can't help but wonder if the mineral oil caused some carbon to break off and lodge in the valve, sticking it open.

 

[AKBill]

I can't help but wonder if the mineral oil caused some carbon to break off and lodge in the valve, sticking it open.

I would say the mineral oil is not the cause. 8 hours on the oil IMHO would not cause that.

 

[FastEddieB]

From the O360 in my Tiger:

Had “morning sickness” in Hartford, CT. Valve stuck over Long Island Sound, leading to VERY rough running and a declared emergency.

 

[k9medic]

Got the plane pulled into the local shop first thing this morning.

They pulled the cowling and the damn bird has built another nest!


2 hours later the cylinder was pulled and the above photo shows the results.

A new push rod and tube arrives tomorrow and it should be back up and running by tomorrow afternoon.


Thankfully no piston, valve or spring damage. The valve was stuck solid according to the mechanic. He’s reaming out the valve guides and doing some other things to the engine.


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[FastEddieB]

A mechanic on Long Island spent quite some time repairing mine. But he did so without pulling the cylinder. He pushed the valve into the cylinder, reamed the valve guide and then fished the valve back out with fishing line - I think. I picked up the new pushrod, guide and associated parts at nearby Mattituck. When all was said and done, when I asked him what I owed, he said, “Maybe an hour yesterday, an hour today, say $50?”

Those were the days!

 

[bkspero]

How many hours on the engine? Enough to trigger Lycoming's SB388c valve wobble test (400 hrs with standard metallurgy guides or 1000 hrs with hardened metallurgy guides)? See this link:

https://www.lycoming.com/content/service-bulletin-no-388c

As I understand it, this is Lycoming's way to catch either excessive guide wear or carbon build up before they cause valve problems. Did the shop ream all the exhaust valve guides? If not, then you might consider having the wobble test done on the other cylinders as a precaution.

 

[DesertNomad]

How many hours on the engine? Enough to trigger Lycoming's SB388c valve wobble test (400 hrs with standard metallurgy guides or 1000 hrs with hardened metallurgy guides)? See this link:

https://www.lycoming.com/content/service-bulletin-no-388c

As I understand it, this is Lycoming's way to catch either excessive guide wear or carbon build up before they cause valve problems. Did the shop ream all the exhaust valve guides? If not, then you might consider having the wobble test done on the other cylinders as a precaution.

Indeed. I had a valve stick open I'm IMC at 10K near El Paso. Not a fun experience but we landed safely.

 

[k9medic]

We rented a car and drove home yesterday since there was a big unknown with the repair time frame. I didn't want to sit around another two days and find out it needed a cylinder.

Since this is not my home base, the mechanic is doing what needs to be done to make sure I get home safely. The bulletin is something I will look into though.

As luck would have it, the weather is crap for the next couple of days. I fly enough in the stuff for a living so no need for me to do it when I'm flying for fun.

 

[Doug Reid]

If you are going to own an airplane, cowl plugs are a must. Even though I keep my planes in an inclosed hangar, birds still are a problem at times. Always look for grass or straw under your cowl and look inside prior to flight. Check your fuel vents on a regular basis as well. Sorry to see your bent push rod...hope you get back in business soon.

 

[bkspero]

One other thought about birds nesting. With the nest being on top of the cylinders it means that the birds entered through the cooling air inlet openings (or the plane has really bad baffling <G>). But for those of us without closeable cowl flaps, entry through the bottom is a potential issue as well. There is a 172 tied down opposite my hangar and one or more birds fly into and out of its cooling air outlets regularly. They are almost certainly nesting. The owner of the plane tied down next to that one put a note on the plane and told the airport owner what is happening in an effort to alert the operator/owner.

From my dim memory of preflighting a 172, there is no easy way to see what is going on in the cowling beneath the engine, so nesting there would be easy to miss. On the positive side, I'm also not sure if a nest there would cause anywhere near as serious a problem as one on top blocking cooling air to the cylinders. Maybe if the nest blocks the outlet opening?

It's easy for me to see underneath the engine when preflighting my Tiger? If I had a plane with fixed outlet openings and a difficult to open cowl, I would probably make or buy plugs for the bottom air outlets as well as the inlets.

 

[flyingron]

From the O360 in my Tiger:

Had “morning sickness” in Hartford, CT. Valve stuck over Long Island Sound, leading to VERY rough running and a declared emergency.

I had one like that (I'm not sure where the pushrod and tube is now), but I've got the cylinder and piston. In my case the valve broke off and bashed around inside the cylinder for the rest of the flight.

 

[MajorTurbulence]

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Dumb me. I was about to ask how a non-mechanic would even know what to look for to determine if a pushrod was bent. I did not know that those rod looking things were pushrods (I thought they were structural support bolts for the cylinders). But now that the picture clearly shows a bent looking rod near a straight one, I see what the pushrod fuss was all about. I now, from this, have learned to inspect those rods when the cowl is off.

 

[flyingron]

Well, the rod looking things are the pushrod tubes (the pushrods are inside).

 

[weirdjim]

There is a redneck guide and seat process. As you said, push the valve back down into the cylinder with a WELL SECURED safety wire. Soak the valve guide with an approved solvent (the initials are MMO) for a day, then refish the valve up into the guide, put a medium speed drill on the tip of the valve stem and "lap" the valve, guide, and seat for a few minutes.

Of course, **I** would never do such a thing, but I have this old time mechanic friend Ernie ...

JIm

 

[Dan Thomas]

I kept birds out of my cowl by wrapping some mothballs in a rag and tying it shut with lockwire. Make a long twist in the wire and cut it long and form a hook. Hang it where you'll see and remove it when you check the oil. Birds hate mothball stink. So do mice. Plug the cowl inlets too, as it prevents any breeze clearing those fumes out. Leave the outlet open.

Birds also build nests in the structure anywhere they can get in. Horizontal stab is popular. In the wing too, if they can get in past the flaps and ailerons. Wheel wells sometimes have openings into the wing structure.

 

[Capt. Geoffrey Thorpe]

I kept birds out of my cowl by wrapping some mothballs in a rag and tying it shut with lockwire. Make a long twist in the wire and cut it long and form a hook. Hang it where you'll see and remove it when you check the oil. Birds hate mothball stink. So do mice. Plug the cowl inlets too, as it prevents any breeze clearing those fumes out. Leave the outlet open.

Good thing you are in Canada...
"It is a violation of Federal law to use this product in a manner inconsistent with its labeling."

 

[weirdjim]

How do you smell mothballs. Do you hold them by the wings?

Jim

 

[iflyvfr]

I kept birds out of my cowl by wrapping some mothballs in a rag and tying it shut with lockwire. Make a long twist in the wire and cut it long and form a hook. Hang it where you'll see and remove it when you check the oil. Birds hate mothball stink. So do mice. Plug the cowl inlets too, as it prevents any breeze clearing those fumes out. Leave the outlet open.

Birds also build nests in the structure anywhere they can get in. Horizontal stab is popular. In the wing too, if they can get in past the flaps and ailerons. Wheel wells sometimes have openings into the wing structure.

Mothballs in the cowl absolutely work. I used to have an open T in farm country so I've had the opportunity to experiment. Do like @Dan Thomas does and you don't need to worry about cowl plugs.

 

[Silvaire]

When I had a stuck valve I had flown from San Fran Bay Area to Amarillo without a hint of trouble. Stopped at Tradewind for gas and when taxiing to the end of the runway for takeoff that’s when it happened, just like that from fine to not fine. Had to leave the plane there and take a Southwest flight back home.

 

[MajorTurbulence]

Outside of a rough running engine that would make one carefully inspect the engine, how often do bent valve tubes appear on a routine inspection. Most I’d guess are probably missed until after a serious event has occurred.

I recall one incident where a stumble on descent happened to me. I saw the egt rise on a particular cylinder but otherwise engine seemed normal until engine run up the next day- it was rough. Turned out one of the Champion plugs had fouled. No problems after changing to Tempests later on return from my cross country, but the symptoms could have been a valve hanging up or a bent valve that might have been able to be diagnosed by looking at the valve tubes. Food for thought.

 

[flyingron]

Birds also build nests in the structure anywhere they can get in. Horizontal stab is popular. In the wing too, if they can get in past the flaps and ailerons. Wheel wells sometimes have openings into the wing structure.

On the Navion, they like to get either right where the elevator carries through or go in that hole and then through the lightening holes into the vertical stab. I had several nests before I put a "Scare Eyes" ball hung from the rotating beacon with a piece of safety wire. Of course, moving to a hangar fixed the problem for good.

 

[Domenick]

I kept birds out of my cowl by wrapping some mothballs in a rag and tying it shut with lockwire. Make a long twist in the wire and cut it long and form a hook. Hang it where you'll see and remove it when you check the oil. Birds hate mothball stink. So do mice. Plug the cowl inlets too, as it prevents any breeze clearing those fumes out. Leave the outlet open....

Unfortunately, birds have virtually no sense of smell. The olfactory sense involves too much heavy, juicy, gooey tissue for compatibility with flight.

Old-fashioned mothballs are either naphthalene or paradichlorobenzene. Both solid substances slowly sublimate into vapor. If the mothballs work at all, I'd guess the engine compartment fills with vapor which actually irritates the bird's eyes.

Cowl plugs and wire screening would also work. Whatever you do, hang a "Remove Before Flight" indicator.

 

[Dan Thomas]

Old-fashioned mothballs are either naphthalene or paradichlorobenzene. Both solid substances slowly sublimate into vapor. If the mothballs work at all, I'd guess the engine compartment fills with vapor which actually irritates the bird's eyes.

Whatever it did to them, it did it well.

 

[MajorTurbulence]

One other thought about inspection of the valve tubes. Undoubtedly, the reason a tube bends is because of excess heat. Unfortunately in the OP’s photo, the condition of the other visible valve tube shows flaking paint, similar to that on the bent tube. If your airplane engine has a nice uniform paint job, can flaking or discoloration of paint on the tube be a telltale of increased frictional force or slop with a resultant heat buildup on that tube giving an early indication of a problem with that valve before bending and failure?

 

[Hang 4]

I suspect if the pushrod tube is bent enough to be visible, you'd know it from the engine running like crap. Pretty sure the bend is from the pushrod having an impact between the cam and a stuck valve. Kind of like hitting it with a hammer.

 

[Doc Holliday]

One other thought about inspection of the valve tubes. Undoubtedly, the reason a tube bends is because of excess heat.

Uh.....excuse me, but WTH?

Unfortunately in the OP’s photo, the condition of the other visible valve tube shows flaking paint, similar to that on the bent tube. If your airplane engine has a nice uniform paint job, can flaking or discoloration of paint on the tube be a telltale of increased frictional force or slop with a resultant heat buildup on that tube giving an early indication of a problem with that valve before bending and failure?

No.

Those tubes contain a pushrod. If the valve sticks, the force of the tappet will push and bend the rod, which in turn bends the tube.