bearing noise

[WAcat30]

My A4 has a bearing noise which is getting progressively concerning. Initially it was only detectable at low RPMs (low engine noise) but it gradually became loud enough to be heard constantly. Most recently it stopped the motor (under high load tests). I recently replaced the aux drive bearing (thanks to Moyer for the detailed notes on the drive and oil level issue). However, upon reinstallation of the aux drive - the noise persists. It seems difficult to isolate the location of the noise since the noise travels through the gear train AND since each component is necessary for running the motor. The noise occurs in all drive states (Rev, Neutral, Fwd). Searching the web/Moyer site, I found one comment that A4 gear train is unlikely the source of a problem. I'm contemplating separating the engine<>drive looking for the problem - but thought I should lean upon the vast experience of the community. Pics of that area of the engine might be helpful as well. Thanks in advance for any assist.

[msauntry]

Hate to say it, but you may have to revisit the aux drive bearing. Mine made a squeeling noise until I replaced it with a rebuilt unit. Maybe something got reassembled incorrectly. Its been known to happen... not to me, of course

Squirt some WD40 on the aux drive bearing and see if it goes away, then do the same for the alternator or remove its belt to rule it's bearing out.

Check your belt tension before hand. Maybe its too tight and is causing the bearing trouble?

[WAcat30]

Possible bearing noise - engine dies - overheating

I've read a few recent similar posts and thought I would update my initial post as well as expand the title; perhaps give reference info to others. I went ahead and pulled the head off my engine RE: I didn't have functional compression (i think that was the term provided in the MMI manual) in two cylinders (2&4; 70 and 80 respectively). The engine would run - bog under load - then eventually overheat and die (but would always restart). Pulling the manifold was a problem; center stud and manifold atomically bonded. Upon breaking the center stud, I realized how much better it would have been to remove the studs (tip for others). The head came off without a problem. Cleaning up the surfaces, I noticed corrosion on #2 and #4 chamber surfaces. Picture attached. I wondered if this is something typical - or if I need to pull the motor (its still in the boat) and have the block milled to remove the corrosion. I hate to remove block material if not needed. The exhaust valves have pitting; I've not yet removed them to determine if the seats have the same. Last note: I'm thinking I could have actually caused the water in the cylinders RE: When i bought the boat the water muffler had a leak at the neck (input). I added a sleeve - but wondered if this could have restricted the exhaust to the point it could cause excessive back pressure in the motor? Sad if true. Additional note, the manifold had a crack/corrosion in the #4 exhaust area. Thanks to any comments/assist in determining the next course of action.

Additional details; 80s late model engine - fresh water cooling - water ingestion seemed to coincide with poor engine performance. Prior to that the engine ran fine.. (sadly). Oh - ps, the bearing noise is still around.... but less concerning at the moment.

[rigspelt]

Pics of that area of the engine might be helpful as well.

Which area did you need pictures for?

[Dave Neptune]

Finding noises

WAcat30, I'm an ole' motor head and have many tricks up my sleeve from years of diagnosing problems. Probably one of the most useful tools I have in my arsenal is a "STETHASCOPE", wanna play doctor? You can buy automotive types in some performance shops and maybe a Pep Boys. You can listen through the "tube" or press a metal probe that is attached to a metal disc that's included against various areas around the motor until you can sort of isolate the noise. It can really help pin-pointing the offender espesially when space is at a premium.

Did you get the water out before tearing it down?

Dave Neptune

[WAcat30]

reference pics

Appologies, I neglected to successfully add the reference pics of my engine. I'm mostly interested in determining whether the corrosion seen in the last 2 pics requires milling of the block to eliminate the rust, OR is removing block material a very bad idea? Thanks for any inputs.

Neptune, I agree - the auto-stethoscopes are great - and I have one (or two?).. however, I wasn't able to isolate the sound RE: gear train. I noticed when spinning the motor by hand I may be hearing the noise in the tranny area. I'll have to open the gear cover and try determining the source again. Thanks for the idea..

Hopefully you can see the attached this time... :

[keelcooler]

Looks like that should clean up without milling. Valve job and some new studs.
Did the motor lock up during a high speed loading and then start turning again?

[Dave Neptune]

To remove or not to remove?

WAcat30, I looked at your pics and quite frankly your block and valves look better than mine did when I purchased the boat. I wound up borrowing a seat cutter and re-did the seats then had the valves ground. I did lap them in a little.
When putting the head back down (2 gaskets) I would recomend that you use Permatex "Aviation" grade. It is an excellent sealer for rough surface sealing. I did mine going on 26 years ago and she's still ticking. Use it on the intake manifold and studes as well, it really "stix" and stays where you put it.
I also took the oppertunity to chip away most of the crude in the block at the same time.
FYI, my block was actually siezed and I had to break the pistons loose with a dead-blow type hammer. The engine is now 40 years old and never been torn down other than when I bought her and that was just removing the head. These are truely an amazingly durable motors with oproper maintenance.

Go 4 it
Dave Neptune

[WAcat30]

tks.

Thanks for the input Neptune and cooler. I'll heed your advices; clean up the valves and reassemble - see if I can get life back into the motor. I'll try and keep an eye on the engine via sparkholes and dental mirrors..

Cooler is dead on RE: the engine locked up with loads (heating) and ran again once it cooled just a little. I didn't have a lot of time to investigate when it died; forced to sail back into the slip.

I'm new to the marine engine world and appreciate the inputs.. many thanks.

[Dave Neptune]

Heat

WAcat30, FYI the A-4 is extremely resistant to overheating damage. Just make sure you have good flow through the block!!!!!

Dave Neptune

[lat 64]

Wacat30,
That valve in pic #4 would make a fine coat hangar. Polish it up nice and paint it some pretty color and drill a hole in your garage wall just big enough to slip it it like a nail.

MMI has a nice new one that you can use in your engine and help stimulate the economy at the same time.

Russ