Intermittent spinnging/grinding noises, sometimes leading to stall (video)

[gregjansen]

Hey Afourians,
I'm looking for advice on my Tartan 34c's A4 issue. It began after an overheating episode when something got caught in the water jacket last year.

Here's a short video.

The noise seems unrelated to throttle/rpm, just kicks in randomly.
I've already replaced the starter, so I don't think that (or Bendix) is the problem. What are your theories and diagnostic tests?

Flywheel gear bent?
Electrical?

thanks in advance for any and all advice,
Greg Jansen

[Mo]

Hard to tell without being there. Need to get the camera down there and try and see where it's coming from. Sounds like a bearing to me.

Things I'd try.
1. Remove the alternator belt and start the engine. If the sound ins't there shut it down and try spinning the alternator fan blades and see if it is rough. You could try grabbing the fan blades in your hand and move it laterally as well. Any play would indicate bearing wear.

2. Once you have that belt off there is a second thing you can try. Take a piece of 2x4 or something and with the engine running, alternator belt still off, press against the accessory drive and see if the noise either stops or gets worse.

That's where I'd start.

[joe_db]

My last odd sound adventure ended up being a bad alternator bearing. Removing the belt was the key to finding it.

[gregjansen]

Testing bearings...

Thanks again Mo,

I did tests (1) and (2) and both were unable to change the sound. In removing the alternator belt I was able to smoothly rotate the fan blades and I was unable to wiggle it laterally. The sounds came and went independent of lateral and frontal pressure with a piece of wood on the accessory drive.

Being down near the engine I could tell that the noise was closer the middle / front near the flywheel, than to the side where the alternator hangs.

It comes and goes until eventually it gets too frequent and the engine looses momentum and stalls out.

Please note, I visit this boat from another state and I'll be on site today and tomorrow. If there is anything else I can try while here, let me know. I've had trouble finding mechanics in the DC area that are willing to work on the A4.

thanks again y'all,
Greg

[Surcouf]

this sounds very strange. You have ruled out alternator.
I know you have replaced the starter, but it sounds like a starter that engages randomely. Do you have a visual access to the starter gear from the flywheel side, to make sure it doesnot try to engage? (removing the flywheel cover?); could be an intermittent short inside your ignition key, sending intermittent close orders to starter?

outside of that, not sure what it could be

[gregjansen]

That intermittent short theory is very interesting and seems promising. Thanks for the feedback!

[Mo]

I'd go to starter next as well.

[gregjansen]

Follow up... Fixed it!

Hey all,
Thanks for your tips on my issue. After performing those tests I removed the flywheel cover plate again and listened to the sounds, intending to observe the starter gear and see if it's engaging etc. When I started it, the sounds were... different.. more of an occasional pinging from metal contact than that grinding sound I had. I figured, okay, these moving parts are getting more familiar.. It's not grabbing the flywheel anymore, just careening off it once in a while, perhaps due to wearing down or the cover being gone.

In any case the sounds was definitely in that starter neighborhood and the gear was no longer engaging. I figured I'd try my spacer scheme, so I removed the starter and inserted two metal hoops around the bolts in between the engine and the starter. (These are from my electrical kit, thin flat hoops for connecting wires to larger battery terminals.)
Anyway, I realize this is not engineering exactly, but the engine started and ran just fine after that. When I sail this engine home to NC, I will machine a plate to put in there or something. (Was there supposed to be a gasket in between?)

So thanks again for all the help. I think I have it "good enough" to get it out of DC without that problem.

Greg