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Why Am I Hearing Gear Noises?

RV7ator

Well Known Member
What could cause this? A whirring, whining noise sounds from the accessory case of a new 375.

Knowledgeable individuals who've heard this say it's not right; I couldn't agree more. Offhand, bearings are dismissed since it's not so much a screeching metallic howl from the engine as gears that aren't properly messed. Frequency modulates with RPM (as you would expect), lowest easily imagined as the teeth engaging - a very fast buzzing - progressing to a smooth whirr then steady whine above 1500 rpm. Think noisy automotive differential.

It's not the ignitions, governor, or alternator; there's no vacuum pump. One fellow says he "feels" it when touching the oil filter and left ignition (P-mag), nothing on the right ignition. We've yet to put a stethoscope to it. Interestingly, the mag gears only engage .15 inch - that's less than half a tooth width - yet I'm told within spec.

From what I read, there are no mesh or lash adjustments in assembling the accessory case. So far, the only thing we can conjure is a canted bearing counterbore that puts the unfortunate gear slightly out of the rotation plane.

Since the engine builder must rely on our description, they're in no better position than the VAF Brain Trust. What do you think I'm dealing with?

John Siebold
 
What do Bart and the boys who built it say?

A true gear whine can come from more than mesh depth. The machined face of the gear is just as important.
 
Interesting...so far

For those who pose questions..

The boys at ASP don't know. Guess so far is " excessive backlash" and "idler gear for movement". No quantification of these metrics. The boys, BTW, doesn't include Bart; he retired early this year. Doug Hamerton takes his place.

What's the concern with an ECi gear? One is, the other isn't, and removing either P-mag doesn't affect the noise.

The engine has only been ground run (other than the test cell) a few minutes four times, oil never getting above 70F. Nonetheless, such as I'm hearing is abnormal and shouldn't be. The hundreds of engines I've operated don't whine at any temperature.

Keep scratching your heads. I think it's a part manufacturing defect, but what.

John Siebold
 
Tach Drive

I had a "whine" that turned out was the tach generator. The drive pin was too long and put internal stress on the guts of the generator.
It was confirmed when my tach gen stopped working(in short order) and the replacement didn't whine. Not sure if you're using the vans tach gen or not but just in case.
Mike
 
Where did you get the gear that you have on your P-mag?

Some of the gears Emag Ignitions distribute were not heat treated properly and wear out prematurely.

Also, when we were developing the EICommander we cut the back half off my old O-290 and used that to spin the P-mags. Only one problem, it was too loud to stand close to. This force us to develop a custom rig to spin the P-mags.
 
If it were my engine it would already be disassembled.

I would second that. While "the boys" have a good reputation, it is not flawless. The accessory case is pretty easy, so why have it in the back of your mind during phase one...take it off and check everything over.
 
Still Interesting, so far...

Noisy oil pumps. Who'da thunk it.

The engine's going to get a good going over with a stethoscope, but unless something definitive is found, it will get flown enough to heat the oil and gather baseline vitals via the engine monitor. 1 1/2 hours in a test cell pretty much eliminates the likelihood of instant failure. ASP is going to get the engine back, nonetheless. I'm not going to touch the internals, nor have a local wrench dig in with parts and labor paid by ASP.

No tach generator involved and the mag gears are not E-mag's.

Any other hunches?

John Siebold
 
Your description of feeling buzzing on the left P-mag is perhaps telling you something... not sure what.

BTW as a data point for those experiencing oil pump growl: Prior to removing the inverted oil system, my pump would growl until oil was something like 60-70F. It most closely resembled the sound a car's power steering pump might make when low on fluid. The sound always was gone during the taxi out, as it only took 10 or 20 degrees F increase in oil temp to quiet it down. I've not heard the growl since removing the inverted system; presumably it is much easier to pull the oil into the pump now. I suspect the noise was from cavitation.
 
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I would not fly it

without confirming and fixing the root cause. After totaling our Mooney in an almond orchard due to an accessory gear failure, I set very high standards on resolving any engine sqwauk ON THE GROUND.

Please learn from my experience.
 
Run this test...

My IO-320 makes the same noise when cold. I preheat my oil with a sump heater before flight and it minimizes the ground run/warm up and 'thuh noise'...

You could repeat this by simply draining your oil, heating it up, and then refill it before starting. (Alaska bush trick). If the noise continues with warm oil, then you've eliminated the likelihood of the idiosyncrasy that many of us in the field are experiencing. It would be time then to give Aerosport a call...
 
That's sorta what I'll be doing today, Joe. The 50-weight goo, even though 60F at start-up, is going to be drained and 15W-50 poured in.

We'll see. (Hear?)

John Siebold
 
Get real John.



Then do it now.

I've got to second Dan's advice here. It only takes a second to end up on the evening news. Quantify everything ASP wants, get a sound recording with data, pull the engine and send it back. New engine,New airframe,known problem = Don't leave the ground in my mind. Plus you bought a $25K+ engine that has a problem = "Right back to the store".
 
A friend's 540 in his -10 whined after each cold start. It sounded like gear noise coming from the accessory case but would only do it on the first start of the day. Subsequent starts would be quiet.

After the first oil/filter change the noise went away and has never returned. While we'll never know for sure what caused the noise we do believe it was the oil filter by-pass valve that was causing the noise.
 
A friend's 540 in his -10 whined after each cold start. It sounded like gear noise coming from the accessory case but would only do it on the first start of the day. Subsequent starts would be quiet.

My friends' RV-10 IO-540 also has a gear mesh whine on cold starts, suspected coming from the oil pump as well. Once warmed up, it sounds like normal. They have nearly 400 hours on this engine now.

My buddy's AT-310 Air Tractor with a freshly rebuilt R-1340 P&W also howled like a banshee with gear meshing noise when cold too
 
That's sorta what I'll be doing today, Joe. The 50-weight goo, even though 60F at start-up, is going to be drained and 15W-50 poured in.

We'll see. (Hear?)

John Siebold
I already use 15-50 and as Alex stated it best it sounds like a power steering pump wine.
 
I've got to second Dan's advice here. It only takes a second to end up on the evening news. Quantify everything ASP wants, get a sound recording with data, pull the engine and send it back. New engine,New airframe,known problem = Don't leave the ground in my mind. Plus you bought a $25K+ engine that has a problem = "Right back to the store".

We don't know that the engine has a problem, let's wait for the "warm oil" test first. :) You might even install a new oil filter, too.

Yes, power steering pump growl is exactly what I was describing in my earlier post. I don't hear it on first start if the engine has been on the heater.

I hope this will solve your "noise problem". Keep in mind you are going to hear a lot more mechanical stuff going on in an uninsulated RV than a certificated plane with the cushy stuff installed.
 
The 50-weight goo, even though 60F at start-up, is going to be drained and 15W-50 poured in.

That's a smart test. It sidesteps the possibility that the noise will go away because of case dimension change due to temperature change.
 
I have heard a noise like what is described coming from the Prop Gov. especially with cold oil and also was always was a Hartzel governor.
Good Luck,
Mahlon
 
Oil pressure relief

I wonder if what is thought to be the oil pump is the oil pressure bypass buzzing. Gear pumps don't produce a linear output, and the bypass sees and reacts to each "bump" or wave of oil when cold.
For sure at least cut the filter open and inspect the sump screen before you do anything else.
Good luck, hope its minor,
Tim
2013 dues paid
 
ASP IO -540

My whines loudly on the first cold start up.
Whine goes away after the oil heats up. I can't tell where the noise is coming from other than to say from the engine compartment and from the sound of it, gear accessory case.
During summer I hardly notice it but now in winter it is very noticeable.
Running 100 Aeroshell and BTW around here it only gets near freezing, never really below.
Not telling you what to do just another reference.
 
Same noise

I've had 2 IO-540's and they both make the same noise on cold start-ups when I haven't been able to preheat the oil. Nothing in the summer.

Vic
 
Interesting. I hear something like the power steering type noise in my IO-540 occasionally. Ive wondered about it but I only get it while taxing back after landing. i dont recall hearing it when cold, but my oil is always preheated in the hangar.
 
Sure Is Noisy Out There

Changing to 15W-50 did not help, and everything was 70F or more before start. Now, goo's still on the gears at start since all I did was drain the sump, but after four minutes of ground run and oil reaching 80, no joy. No change in sound character during the run as the oil morphed grade and temp; frequency variable with rpm as always.

I'm truly surprised by the amount of racket out there. I've never encountered this phenomenon before and I've started many a freezing cold engine. Four previous -7s and a bunch of other RV rides were stone silent (except exhaust, propeller, the usual stuff:rolleyes:).

Mahlon, I've considered the governor. Until we can stethoscope the engine, no telling. I did have it run through our local prop shop to assure it was adjusted and clocked for the horsepower and position of the installation, so not overly suspect. It's a Jihostroj.

For you "hot oil, noise went away" crowd, how hot is hot? Some say ambient variation (winter/summer) was sufficient, but did anyone have to wait until close to normal 180 operating temps?

Next announcement after scoping the engine, which may be many days. Do a search if not among the daily posts.

John Siebold
 
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Changing to 15W-50 did not help, and everything was 70F or more before start. Now, goo's still on the gears at start since all I did was drain the sump, but after four minutes of ground run and oil reaching 80, no joy. No change in sound character during the run as the oil morphed grade and temp; frequency variable with rpm as always.

I'm truly surprised by the amount of racket out there. I've never encountered this phenomenon before and I've started many a freezing cold engine. Four previous -7s and a bunch of other RV rides were stone silent (except exhaust, propeller, the usual stuff:rolleyes:).

Mahlon, I've considered the governor. Until we can stethoscope the engine, no telling. I did have it run through our local prop shop to assure it was adjusted and clocked for the horsepower and position of the installation, so not overly suspect. It's a Jihostroj.

For you "hot oil, noise went away" crowd, how hot is hot? Some say ambient variation (winter/summer) was sufficient, but did anyone have to wait until close to normal 180 operating temps?

Next announcement after scoping the engine, which may be many days. Do a search if not among the daily posts.

John Siebold
Ya, the problem is that none of us are there to hear your engine in person, I know mine will wine on the firs start on an 80F day, I can exactly say at what temp it goes away. One thing, I hear my wine while wearing an ANR headset; I don?t think it is audible without the headset.

To stethoscope your engine all you need is a long screwdriver, put the tip against the place you want to listen to and put your ear against the handle, this works very well.
 
engine whine

My IO 360 C1E6 whines, noisy, on cold startup, whine/ noise builds and then goes quite and sounds perfect. Been doing this for over 250 hours. My mechanic is stumped even with stethoscope. Could not isolate it. Pulled #2 cylinder today and will look inside tomorrow. Wondering if hydraulic lifters could be it. Mystery!
Tim
 
Fresh News

Stethoscoped the engine today. The governor seems the source. The buzz/whirr/whine certainly emanates all along the body and most loudly from the housing aft end. Not so much around the engine. But this doesn't necessarily exonerate the driving accessory gear until the governor itself is checked out. It's a PCU5000 (aka Jihostroj).

It was put on a test stand prior to installation to assure proper performance. Prop shop gets a call Monday.

BUT! Oh, my goodness! #1 and #3 each have loud tappet noises, seemingly one each judging by the tempo. ASP still isn't out of the woods. Oil temp was 80F and CHTs were well into the 200s at shutdown after five minutes with up to 2000 rpm. Plenty of time to pump up lifters (and they shouldn't have been flat, anyway).

Aaarrgh!

John Siebold
 
Some times what you think is tappet noise is really normal piston slap. If you take the rocker covers off and the valves have 0 lash, the lifters are pumped and it might have been piston slap you heard. Normal piston slap can be pretty loud, especially at idle speeds. If the governor is the whine, it is probably ok and not defective. They all seem to whine a bit some louder then others.
Good Luck and Happy New Year,
Mahlon
 
Thanks, Mahlon,

I'll dig deeper on the governor noise.

The valve train noise is only 1 and 3; 2 and 4 are quiet. Also, it's half the rpm. Piston slap would be the same as rpm, no? I'm going to have better educated ears listen.

John Siebold
 
Any more on source of gear noise?

I also seem to have gear noise on cold oil. My engine is an IO-360 A1B6. Any more information on the source?

Thanks,
Jay Martin
 
A friend with a 10 had a gear noise on startup, but only on startup. Once it was warmed up it went away and did not happen till the next cold start. We checked everything but came up with nothing.

Then the first oil/filter change occurred and the noise went away. It was the filter!
 
Straight cut gears

The S2-B i fly makes the same noise. All the gears in the accessory case are straight cut gears. Ever notice in a manual transmission car the reverse gear whines? They are straight cut gears. The rest are helical cut gears like the ring and pinion. Designed that way to be quiet.
I'll bet thats what your hearing.

Eddy
 
Also, it's half the rpm.
John Siebold

I am curious how you determined this. At 600 RPM, there are 10 revolution events per second. Can you really count that fast?

Further, I don't believe that piston slap will always occur on each stroke. Some times it will only slap on the power stroke (half the RPM). It really depends on what is causing it. I once had a noise at idle on a big block chevy. I was pretty sure it was valve train related. Sure enough, it was piston slap. In my case, the piston pin was tight in the piston bore, causing slap on each stroke. I was led to believe that slap caused by excessive clearance will only occur or be more noticeable on the power stroke.

Larry
 
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