Unusual noise - please help diagnose

[tomfreo]

My 1961 beetle has begun making a loud unusual noise.

It appears to be coming from the generator although it could also be coming from the fan. Frankly I really can't tell where the noise is coming from.

I thought it might be the tappets but they all seem good at c.0.005-0.006".

I recently changed the fanbelt. I thought it might be the generator bearings although I doubt it would make the 'click-click' noise I'm hearing.

I can detect no difference in the running of the car.

The noise disappears when the engine warms up. After twenty minutes driving, with the engine at idle, I can detect no discernible noise.

This has me perplexed and worried. It is my daily driver. It started making the noise yesterday and continues to make the noise every time I start the car.

Here is a video of the engine running:


Link


And here is a video of fanbelt tension:


Link


https://youtube.com/shorts/gxsYzjFDC18?feature=share

Please help me diagnose.
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'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[EVfun]

Since it is a cold only problem give it a brief cold start without a fan belt. Shut the engine back down pretty quickly but you should be able to tell in 30 seconds if the noise goes away. The goal here is to split the problem in half. Fan belt up or the engine itself.

I couldn't hear it too clearly in the video. For a bit it sounded like and exhaust leak in 1 cylinder but then not so much. I'm wondering about a loose flywheel. Last time I hear that it was a kinda double click (cl-la, cl-la, cl-la) and most noticeable at idle. Mine didn't go away after warming up though.
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[mukluk]

It almost sounds like the voltage regulator body is rattling or maybe the contacts inside chattering.

I'd agree with EVfun, do a cold start with the belt removed to see if the noise is still present or disappears with the generator and fan not spinning.
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1960 Ragtop w/Semaphores "Inga"

[67rustavenger]

[tomfreo]

Ok thanks good thinking. I'll take the fanbelt off and give it a whirl. I'll report back once done, probably six hours or so.
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'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[Eric&Barb]

Wonder if some welds inside the muffler have given away. Then when really hot it expands and quiets down.
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In Stereo, Where Available!

[MrGoodtunes]

If test #1 (run without fan belt) gets rid of the noise, then test #2 might be:

• Re-install fan belt & start engine (expect noise returns)
• Grab upper left and right of fan shroud with both hands
• Push, pull, and twist the shroud, does noise change?

[rcooled]

[tomfreo]

I took the fanbelt off and the noise stopped. Put the belt back on and tried pushing and pulling on fan shroud. No change in noise.

Some notes. If I increase engine revs the noise fades away. The noise also disappears after only ten minutes of running (maybe sooner but that's how long it took me to run down to the shops yesterday).

Here's another video. In it I vary the revs. You can hear the noise going away and coming back. Although I got to say, the audio in the video is not as obvious as when you're standing behind the engine.


Link


I did fashion a 'stethoscope' from a piece of tubing but couldn't locate the sound.

[EVfun]

Move a couple of shims so the fan belt is quite loose and test again. That would suggest generator bearings, and it might be why it suddenly happened when you changed the belt.

I am very happy for you that the sound was not a loose flywheel, it often means the crankshaft and flywheel are garbage and the engine will be getting a full tear down and rebuilt.
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[tomfreo]

[Bill64]

With the fan belt removed, you could check for excessive play in and out and side to side of the armature. Also spin the generator pulley to check for noise, roughness, etc.

[tomfreo]

Belt off, engine off, spun generator/fan - no noise, nice and smooth. However, reaching behind to fan and pulling seems there's some play.


Link


Found another spare belt. Sizes different!! G'gld Dunlop V559 and got spec of 15.44×36.07". Don't know WTF the first number is but the second presumably is length and comes to 916.18mm. Measured the width of the belt with rule and got 9.5mm.

Replaced this Dunlop belt with the spare (no markings apart from 'Banda' and 'Japan') and noise is gone! Fucking ace.

Sorry for all the drama. However …

I read that fanbelt tension play should be 1.25~2cm. The Dunlop belt had play of 1.25cm. The new 'banda' belt has play of 1.25cm.

Also read that play should be as loose as possible without slipping. Any comments?

Also, please view/listen to video (above) for sound when I reach behind to fan and pull on it. Is this bad?

And this video pulling on generator pulley. Is this bad?


Link


Video spinning generator pulley.


Link


Video belt off.


Link


New 'banda' belt on - noise gone.


Link


I'm aware that audio is not great. Squatting behind beetle with engine runnign the difference in the sound is obvious. In the video, it is not. The video audio of me pulling on fan and generator pulley, however, the sound seems magnified and much louder than I remember.

(And, question is, why do links to 'shorts' youtube vids not render properly?)
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'77 Kombi 2L dual carbs
'61 Bug 6V 1600sp

[Bill64]

I checked the movement on my generator pulley with the belt off. It spins freely with no noticeable in/out movement at all. In your last 10 sec video with the clunking sound, if that is the in/out play, I would say that is excessive. That said, I’m glad your noise went away for now. I would be very suspicious of your generator as the cause of your noise if it returns. The brushes may be intermittently contacting areas on the commutator where they normally wouldn’t contact or the fan may be making slight contact on the shroud with that much movement. If the noise returns, I would also look through the big opening in the generator at the brushes as they contact the armature and see what’s going on as the noise comes and goes. Good luck.

[VW_Jimbo]

Get a mirror and have a peak inside, at the front of the fan. Do you see any rusty spots? Powered rusty spots? I am betting the fan has broken at the hub. Not uncommon.
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[Bill64]

I agree with your comment “loose as possible without slipping.”

[carcrazed]

Sounds like a generator bearing. I would rebuild it or get a new one.
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1965 Herbie Replica. 1776cc dual Kads.
1961 Beetle 33,000 Original Miles

"Just When you think you are getting ahead, you're always wrong."

[glutamodo]

When I've had odd sounds from that area I'll do a push-pull on the fan shroud at idle and see if the noise changes.

Now one thing that I'm surprised no one has mentioned is to ask if this engine has the original thermostat setup, the big-ass pivoting venturi ring that throttles down the air intake of the engine when cold. If that is out of adjustment it can rub against the fan. However I've only ever seen this sort of ting happen it was with a hot-open thermostat, not cold-closed.
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Andy T.


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[tomfreo]

Thanks for all you guys help. Swapping out the fanbelt has stopped the noise so I'm going to leave it for now.

[VW_Jimbo]

I believe that the fan is broken. It fractures under the nut and washer. Hard to see, but the tell tail rust trails are always there. The noise is a deep rumble noise with no pattern. Once you tune into it, IT is easily defined.

Pull the 4 6mm bolts, pull the alt strap and remove the assembly. Then remove the cooling fan nut and washer (probably installed wrong) and look for fractures.
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!