Intermittent Whine

[hanleyclifford]

A problem has developed with Destiny's engine about which I want to get opinions from the forum. An intermittent whining or crying has developed, most noticeable running in neutral. I have eliminated the alternator bearings by running with belts off. I eliminated the accessory drive by changing out with another unit with new front bearing and drain hole modification. This seems to leave main bearing or pilot bearing but I would appreciate any comments from the forum. The main bearings were not changed in the last tear down because they were within specification and looked good. I did note, however that crankshaft end play was .016". Perhaps this is the problem? Does anyone have any experience with this sort of thing?

[Mo]

Hanley,
Do you have a camera that takes video. When Hanley comes looking for answers this must be something different for sure.

[hanleyclifford]

Mo - I have a Fuji FinePix camera model A345 which I think can do that. My computer whiz daughter is coming for the week end so I will see if I can get an audio on this sound. I have some suspicions about the problem but I thought I might get some objective reactions from some of the Afourians who have experienced this noise.

[ndutton]

Having zero experience with such an issue I have very little I can offer of substance BUT (there's always a BUT, isn't there?) I think I'd check one more external component hoping for an easy fix or at least eliminating the possibility: the distributor. Do you have a spare you can swap out for a test?

Dumb question because I've never been into this area but can the engine be run with the reversing gear removed? You see where I'm headed.

Beyond that, I can't explain why but I'm thinking camshaft or it's drive gears rather than crank but (Heaven forbid) if you're getting into her that deep you may as well address both.

[Mark S]

An intermittent whining or crying has developed, most noticeable running in neutral.

"Intermittent" meaning what exactly, it comes and goes, there one minute and gone the next with no apparent rhythm?

Mark

[hanleyclifford]

Neil - I had not considered the distributor, but yes I do have a spare and will eliminate that possibility. Cam bearings are all brand new. I have enough stuff to whip a short block together quick and a whole month to do the swap. It occurred to me that I'm being punished for going to that 3:1 alternator drive (last trip I ran 2:1) with same alternator. Also, I do a lot of charging in neutral - tough on pilot bearings, but I could do that job in the boat. Just wondering if anyone has dealt with a similar noise.

[ILikeRust]

Dumb question because I've never been into this area but can the engine be run with the reversing gear removed?

I don't see why it couldn't. Open up the rear housing, pull the reversing gear out, close the rear cover back up (so you don't have oil splashing out or anything falling into the crankcase). The rear end of the crank shaft is supported in a main bearing forward of the reversing gear.

The only thing I wonder is the extent to which the engine was designed to make use of the flywheel effect of the rotating mass of the reversing gear housing. The reversing gear housing rotates in unison with the crankshaft when the engine is in neutral. That's a few pounds of steel spinning at, say, 1000 rpm. I wonder if that spinning mass enables the actual flywheel itself to be slightly lighter - i.e., might the engine run slightly rougher with that rotating mass removed?

No idea.

But as far as can the engine physically run without the reversing gear in place, I don't see why it couldn't.

Interesting idea...

[ILikeRust]

While we're isolating external components, have you eliminated the water pump as a possibility?

We're trying to help you out here to not have to open up the engine...

The other thing I can think of is gear whine somewhere. You've got the camshaft gear meshing with the crank and the idler gear meshing with the crank and accessory drive. If there is excessive lash in between the mating gears, or if they are not aligned quite right, you can get whine. Seems kinda doubtful, though...

[Dave Neptune]

Whiner?

Hanley, a whine is usually either from gears or a bad "ball bearing" going out. It can also be developed by the prop but for that you would have to be in gear and this is not the case. I really don't see how the distributor could whine at low RPM's and it is driven by the accy' drive.
I suspect unfortunately that the "end play" of .016 could be the culprit. I don't know the spec on the A-4 off the top of my balding head but .016 seems a bit much. And that could as the load changes be running the gears on a spot that hasn't been run on and a harmonic whine developes.
Have you tried a stethascope? Could it be someting in your trans as you have the reduction unit?
I'm sure you checked this but I'm going to through it out anyway~~one of the "electric" pumps?

Dave Neptune

[Don Moyer]

Hanley, following Dave's suggestion regarding the potential for gear noise, we sometimes suggest taking a piece of wood (a short piece of 1 by 4 works well) and prying against the alternator drive pulley of the accessory drive. If the idler gear or the two adjacent gears (or even the bushing of the idler gear itself) are "singing", the noise will usually change rather profoundly.

[hanleyclifford]

Thanks for the replies. Mark - By "intermittent" I do mean random and unpredictable. The noise can start unexpectedly and continue for as long as a minute or as little as a few seconds. Bill - I have never run an A4 without the gear unit in but that would certainly eliminate the pilot bearing and the planetary gears and gearcase bearing. Now that you mention this, while on the hard I ran the engine a lot but with the gearcase in forward and did not notice the noise...hmm. Dave - Yes, the .016" end play weighs on my mind now (spec is .002"-.003"). I thought I could get away with this because the engine did not have the noise last trip. Clearly the crankshaft gear could be changing position and thus it's interface with both camshaft and idler gears or even the oil pump drive gear The electric raw water pump was changed and eliminated.. Don - Thank you for that test idea; I will do it next.

[jpian0923]

Hanley, the A4 (of which you are an expert) is much more complicated than the camera.

Figure out the camera first!

We want to hear and see the problem. Nobody wants to wait for the weekend.

[Mark S]

Hanley,

I would think that noise from the crankshaft endplay would be constant, not "random and unpredictable," which to me sounds like bearing or gear noise. I'll bet Don's test will be instructive.

Mark

[ILikeRust]

I hear an intermittent whine only when my wife and daughters are on board.

[Don Moyer]

Hanley, hearing that you only ever hear the noise in neutral is a bit perplexing and renders the side load test I mentioned earlier rather irrelevant, since the idler gear and its neighbors don't have any way of knowing whether you're in neutral or forward.

In that same regard, I don't know how the crankshaft would know whether or not you're in neutral or forward (let alone care), which would seem to sooth your concern over crankshaft end play, main bearings, etc.

It appears to me now that one of your earlier instincts is coming more into focus, which was to suspect the pilot bearing and/or the pinion gears within the gear cage assembly. Can you get to a "now you have it, now you don't" spot as you slowly and sequentially ease the shifting lever against and then away from engaging the forward clutch assembly (not quite to the latching mode) when the whole reversing gear assembly begins to turn as a solid piece of steel?