Not a great day...help with diagnosis

hish747

hish747

Pre-takeoff checklist
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Hish747
First off, it's much better than it could have been as nothing happened while flying. Friday, I flew in my PA28-140 with a 160hp O-320-D2A, to a Class D airport about 37 miles away with no GA service (KORH) for some work . Worked in the area for a couple of hours and when I returned and started up to depart, the engine was vibrating stronger than before. It was also much louder than normal which may have contributed to the apparent higher vibration. I tried leaning the mixture, using carb heat and running on either mag. None of this made any difference. The vibration and noise continued through the run-up. A couple of A&P/pilots passing through stopped by to try to lend a hand and suspected a stuck valve on one of the Cylinders. I hoped against hope that the issue may clear up and so I started up again and of course no difference.

Wife drove out to pick me up from an hour and a half away. Embarrassing, not to mentions lowers her confidence in the safety of flying.

The next day I drove out with an A&P and we ran a compression check. Everything checked out with all Cylinders testing around 70/80 cold. Air was passing through properly when it should so there was nothing stuck closed. I tested power and it made 2400rpm on the ground so it seems that all cylinders must be firing at full power. But the noise and vibration persisted. Mag test at 1800rpm results in a drop of about 100 rpm on both mags.

Some background:
-Engine has 2400 hrs SMOH (Mattituck 2004)
-3 Cylinders are 900 hrs and 1 is 300.
-The is a sign of a slight exhaust leak out of the #2 cylinder as there is whiteness on the bottom spark plug and wiring harness.
-The day before a different A&P adjusted the mag timing although it wasn't that far off.
-Engine mounts seem good.

At this point the plane is stuck at an airport with no GA maintenance and each trip to get a mechanic out there is major ordeal. The most competent mechanic I know "doesn't do road trips anymore".

Can anyone suggest diagnostic steps or what might be happening? Could someone recommend an A&P not too far from KORH with good diagnostic skills? If it appears that it is an induction leak, I assume this would not be a flyable airplane until repaired but can this be repaired without being in the shop?

Thanks for listening.
Hish
 
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hish747 said:
First off, it's much better than it could have been as nothing happened while flying. Friday, I flew in my PA28-140 with a 160hp O-320-D2A, to a Class D airport about 37 miles away with no GA service (KORH) for some work . Worked in the area for a couple of hours and when I returned and started up to depart, the engine was vibrating stronger than before. It was also much louder than normal which may have contributed to the apparent higher vibration. I tried leaning the mixture, using carb heat and running on either mag. None of this made any difference. The vibration and noise continued through the run-up. A couple of A&P/pilots passing through stopped by to try to lend a hand and suspected a stuck valve on one of the Cylinders. I hoped against hope that the issue may clear up and so I started up again and of course no difference.

Wife drove out to pick me up from an hour and a half away. Embarrassing, not to mentions lowers her confidence in the safety of flying.

The next day I drove out with an A&P and we ran a compression check. Everything checked out with all Cylinders testing around 70/80 cold. Air was passing through properly when it should so there was nothing stuck closed. I tested power and it made 2400rpm on the ground so it seems that all cylinders must be firing at full power. But the noise and vibration persisted. Mag test at 1800rpm results in a drop of about 100 rpm on both mags.

Some background:
-Engine has 2400 hrs SMOH (Mattituck 2004)
-3 Cylinders are 900 hrs and 1 is 300.
-The is a sign of a slight exhaust leak out of the #2 cylinder as there is whiteness on the bottom spark plug and wiring harness.
-The day before a different A&P adjusted the mag timing although it wasn't that far off.
-Engine mounts seem good.

At this point the plane is stuck at an airport with no GA maintenance and each trip to get a mechanic out there is major ordeal. The most competent mechanic I know "doesn't do road trips anymore".

Does anyone suggest diagnostic steps or what might be happening? Could someone suggest an A&P not too far from KORH with good diagnostic skills? If it appears that it is an induction leak, I assume this would not be a flyable airplane until repaired but can this be repaired without being in the shop?

Feels like I'm rambling now so I'll stop here.
Thanks for listening.
Hish
Click to expand...

The voices in my head say exhaust. Manifold? Muffler?
 
PaulS said:
The day before A P adjusts mag, day after you have problem? I'm thinking that is the first place I would look for an issue.
Click to expand...

:yeahthat:

Did the mechanic you brought out re-check the timing? Or did you check if either of the mags can be moved (turned) even slightly by hand?
 
The mags are solidly attached and do not move at all. I could feel some excessive vibration before which made me suspect mag timing and so that's why I had that done. Also, the outbound flight to KORH was after the mag timing and seemed fine.
 
hish747 said:
The mags are solidly attached and do not move at all. I could feel some excessive vibration before which made me suspect mag timing and so that's why I had that done. Also, the outbound flight to KORH was after the mag timing and seemed fine.
Click to expand...


Good you checked that.

Is the presumed exhaust leak on #2 at the exhaust manifold flange where the gasket meets the head? If so, and it actually is leaking between the gasket and the head surface, it can erode that surface and you will have to pull the head ($$!). So even if the problem proves to be something else, be aware you do not really want to fly it too much more in that condition.

You might try changing out the gasket on #2 cylinder to see if you can seal the leak. Be careful as exhaust studs corrode and the nuts can be frozen, and you do not want to break a stud. So use plenty of penetrating oil if the nuts don't turn relatively easily - I prefer Mouse Milk for this.

Maybe @Tom-D will have some ideas as well for you.
 
I wonder if the A/C is in compliance with 70-16-05 PIPER:
 
Hi Tom,
Thanks for the suggestion. My PA28-140 has a serial number outside (above) the range specified in the AD. Do you think it's still worthwhile to remove the muffler and inspect?
 
Make sure the Primer is all the way in and secured. Once mine had backed out and gave me your symptoms.
 
Have you carefully inspected the propeller and spinner?
 
Primer was in and locked. Also just had the prop dynamically balanced a month ago. Hard to imagine something happening to the prop since then that isn’t noticeable on a preflight.
Thanks for sharing your thoughts.
 
hish747 said:
Primer was in and locked. Also just had the prop dynamically balanced a month ago. Hard to imagine something happening to the prop since then that isn’t noticeable on a preflight.
Thanks for sharing your thoughts.
Click to expand...
Check that the prop is in good shape. IIRC the dynamic balance involves installing weight. Washers on the prop bolts? I dunno. but either way, the spinner and prop were messed with recently. Would be worth a looksee.
Keep us posted as to what you find.
 
weirdjim said:
How could it be anything having to do with the ignition if the mag drop on both sides is within limits and identical?

Jim
Click to expand...

It sounds like a timing issue, misfiring, or partial combustion issue from the description, and given the fact that the previous day the mag timing was adjusted sure makes it seem like an ignition issue of some sort. You think it's a flat spot on his nose gear, instead? :)

I'm just curious if it could be a mag issue... something weird, like one of the mags is grounded when it's on "Both" and opens up when it's isolated, or someone switched the P leads when they retimed them the day before... I don't know. Just guessing. Like most everyone else in this thread. ;)
 
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No leads were disconnected or disturbed. The mags were only rotated for alignment. There actually wasn't much of an adjustment at all.
 
Seems to me that Tom has had the only real informative response to this. Looks to me like Mr. Piper had a bit of a problem with its mufflers around this time, aircraft serial number or not. Let's see now, engine produces normal power, mag drops are normal, engine (except for noise and perceived vibration) apparently performs as specified. Now let's think that the engine appears normal except for noise and perceived vibration. What could cause that? What on the airplane muffles the engine bark? And psychologically does way excessive noise sensitize some of our other perceptions into perhaps feeling "normal" vibration into abnormal? Or perhaps does a busted baffle or internal muffler weld shake around a bit and actually cause some elevated shaking? The only way to really tell is to do a full inspection of the internals of that muffler. This is the mechanic in me talking.

Me? I do a full runup and do an aborted takeoff run just before I lift the nose. If all is well, I taxi back to the runup area and do another runup, and if normal, a normal takeoff and climb to well above terrain altitude directly over the departure airport. Say, near the service ceiling of the airplane. Then I hopscotch to my home drome via airport under me to airport under me, land at the home drome and get the problem looked at by my own mechanic. This is the 5000 hour pilot in me talking.

If you ain't comfy with that, pull the wings off, put it on a trailer, and take it home that way. This is the cautious pilot in me talking.

I'd be happy with either of the last two solutions.

Jim
 
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Since the OP has not mentioned a cause, I'll throw another guess out there, engine mounts?? I believe I would do what wierdjim mentioned, but that's just me.
 
Jim,
You actually read my mind about doing a runup and aborted take off and then climbing up above the airport and following airports home.

As an update, I flew a different mechanic to KORH. We replaced a couple of exhaust gaskets that looked iffy. One of them clearly had a hole that you could fit a safety wire through. We inspected the exhaust system for leaks and none were found. He did a rudimentary inspection of the muffler but didn't take it off and look at the inside. He just removed some hose and looked in and thought everything looked okay. After replacing the gaskets, it seemed to quiet things down a little but still far from normal.

We inspected the engine mounts and they seemed solid. The mechanic commented that he was surprised at how soft the rubber was. I think that would ease vibration if anything.

Finally, I did carefully inspect the prop and saw no nicks. The mechanic who came with me was outside the plane and said that at full RPM, the prop and spinner were true and straight.

I don't know if it would be helpful but I took a video of the me running the airplane which includes hearing the sound. I could post it to youtube and provide a link if it would help.
Hish
 
hish747 said:
Jim,
You actually read my mind about doing a runup and aborted take off and then climbing up above the airport and following airports home. As an update, I flew a different mechanic to KORH. We replaced a couple of exhaust gaskets that looked iffy. One of them clearly had a hole that you could fit a safety wire through. We inspected the exhaust system for leaks and none were found. He did a rudimentary inspection of the muffler but didn't take it off and look at the inside. He just removed some hose and looked in and thought everything looked okay. After replacing the gaskets, it seemed to quiet things down a little but still far from normal. Finally, I did inspect the prop and saw no nicks. The mechanic who came with me was outside the plane and said that at full RPM, the prop and spinner were true and straight.

I don't know if it would be helpful but I took a video of the me running the airplane which includes hearing the sound. I could post it to youtube and provide a link if it would help.
Hish
Click to expand...

Did you replace the batteries in your headset? Did the mechanic say it was ok to fly? Seriously though, check your headset, make sure the cups are sealed and they are not cracked or anything. If the mechanic said ok to fly, then I would proceed as you said in your first sentence.

Edit: And Worcester is 1000 feet msl, maybe you are sensing that??
 
On closer inspection using an optical tach the mag drops were 120 left and 150 right. I guess the mechanical tach isn't accurate.
If anyone wants to hear what the engine sounds like I''ve uploaded a video here:

Engine & Mag Run Video

It may be hard to discern from the video but I'm wondering if folks think it sounds like exhaust or something else like mags perhaps?
 
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Oil looks ok? Don’t jump to conclusions, but a filter check is cheap to rule out oil side dis-integration.

I’d call that a bad exhaust leak or rod knock if it were on a car (or loose torque converter, automotively...could a loose prop cause anything similar airplanically?).
 
Remove and inspect the muffler as others have suggested. Sounds like a broken internal baffle to me. Look up the exhaust with a good strong flashlight may give a clue.
 
Sounds like an exhaust issue. I’m not familiar with this thing called a..... muffler? I have a veterman crossover straight exhaust system on my RV. Is it possible to remove the muffler and temporarily connect a straight exhaust pipe in its place and run it up again?
 
Just wanted to give a minor update. I flew the plane to another airport that I frequent for service. No issues at all with the flight. The plane made full takeoff power, I climbed to 6500ft above the airport and hopscotched airports over to 7B2 where it will be looked at. Aside from the higher than usual noise, it was a beautiful, smooth and uneventful flight. Thanks to all who chimed in and I'll update once we nail down the suspect.
Hish
 
hish747 said:
Hi Tom,
Thanks for the suggestion. My PA28-140 has a serial number outside (above) the range specified in the AD. Do you think it's still worthwhile to remove the muffler and inspect?
Click to expand...
Sorry for the late response, Yes I'd have a look. see if you have a loose baffle that may be covering exhaust port.
 
A compression check is not a good way to detect a stuck valve, which often occur around 300-500 hrs of cylinder time. There is a Lycoming SI (No. 1426A) on how to check and correct the situation, which folks often refer to as morning sickness. It often clears as the engine warms up but can eventually cause cylinder damage.
 
weirdjim said:
How could it be anything having to do with the ignition if the mag drop on both sides is within limits and identical?
Click to expand...

It doesn't make sense to me, but I was having an engine vibration too. Mags were overhauled at annual about 7 months ago, but after wearing things in they had drifted to 19.5º (they're supposed to be at 22º) Correcting the timing fixed the vibration.

Like I said, doesn't make sense to me, but there it is.
 
Well, the culprit has been identified...It turns out it was an intake leak! When the wrench took off one of the intake pipes, the gasket just fell apart. After replacing it, the A&P indicates the engine ran great. I plan to have them all replaced. Relieved and very thankful for everyone's input!
 
hish747 said:
Well, the culprit has been identified...It turns out it was an intake leak! When the wrench took off one of the intake pipes, the gasket just fell apart. After replacing it, the A&P indicates the engine ran great. I plan to have them all replaced. Relieved and very thankful for everyone's input!
Click to expand...

You gotta like a simple fix.
 
I was thinking it could have been in the OP's head until I heard the video. Nice to hear the "rest of the story". As a bonus, now everyone has an idea of what an intake leak can sound like, win/win!
 
iflyvfr said:
I was thinking it could have been in the OP's head until I heard the video. Nice to hear the "rest of the story". As a bonus, now everyone has an idea of what an intake leak can sound like, win/win!
Click to expand...

I was kind of thinking the same thing, I guess that is why a picture is worth a thousand words, a video with sound is worth a million words. Great job OP, glad it is fixed.
 
weirdjim said:
Seems to me that Tom has had the only real informative response to this. Looks to me like Mr. Piper had a bit of a problem with its mufflers around this time, aircraft serial number or not. Let's see now, engine produces normal power, mag drops are normal, engine (except for noise and perceived vibration) apparently performs as specified. Now let's think that the engine appears normal except for noise and perceived vibration. What could cause that? What on the airplane muffles the engine bark? And psychologically does way excessive noise sensitize some of our other perceptions into perhaps feeling "normal" vibration into abnormal? Or perhaps does a busted baffle or internal muffler weld shake around a bit and actually cause some elevated shaking? The only way to really tell is to do a full inspection of the internals of that muffler. This is the mechanic in me talking.



Jim
Click to expand...

That was a nice guess, @weirdjim, but you were off the mark. ;) Hlad to hear the OP got the problem taken care of relatively easily!
 
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