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Sudden new engine sound help
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EVfun
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PostPosted: Tue Mar 09, 2021 4:25 pm    Post subject: Sudden new engine sound help Reply with quote

I can't figure out what it is but it started suddenly today when I started the car to head home from work. Others didn't notice it, it's not loud but a sudden new sound is concerning. The engine is a stock 36 horse. Making the sound harder to track is that the pea shooter on the right blew its guts out earlier this winter (not the heat riser exit side.) I also have a small exhaust leak at one of the j-pipe clamps. Things to fix when it's more fun to work in the driveway.

The sound happens when I let off the throttle, and is kinda a growling sound. Perhaps a little of a metallic growl. I shut the engine off and verified the oil pressure light was on before cranking and off after starting. When I got home I grabbed the pulley to check end play, unchanged at about 6 thou. The engine seemed to start and drive fine. I'm pretty sure it was worse when cold an quieter when I got off the freeway (but still present) but might be more about being a sudden change and in a quieter place. Your ideas are appreciated.
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PostPosted: Tue Mar 09, 2021 6:13 pm    Post subject: Re: Sudden new engine sound help Reply with quote

I had something similar, just a different tone. It ended up being leaves in cooling fan. Just a few changed the normal sound. Also check the integrity of the cooling fan nut, sometimes right before a fan lets go it makes a noise
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PostPosted: Tue Mar 09, 2021 10:14 pm    Post subject: Re: Sudden new engine sound help Reply with quote

Check the nuts holding the rocker on, I have seen that make a weird noise.

eQ
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PostPosted: Wed Mar 10, 2021 5:31 am    Post subject: Re: Sudden new engine sound help Reply with quote

These “Sound” threads always remind me of a book that I used to read to my kids called ‘I See A Sound’. 😊
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EVfun
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PostPosted: Fri Mar 12, 2021 3:37 pm    Post subject: Re: Sudden new engine sound help Reply with quote

anthracitedub wrote:
These �Sound� threads always remind me of a book that I used to read to my kids called �I See A Sound�. 😊

Searching for sound threads is no fun either. Everyone describes it differently, making searches mostly futile. I did find a John Muir collection on the internet.
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PostPosted: Fri Mar 12, 2021 4:19 pm    Post subject: Re: Sudden new engine sound help Reply with quote

If you can get it to make the sounds in your driveway, use a "redneck stethoscope" (hose in your ear) to localize it. It's actually amazingly useful!
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PostPosted: Sat Mar 13, 2021 5:57 pm    Post subject: Re: Sudden new engine sound help Reply with quote

EVfun wrote:
... sound happens when I let off the throttle ...


So, RPMs would presumably be decreasing; does the sound's pitch also decrease? If you downshift, then letting out clutch would increase RPM's; does the sound's pitch also increase or maybe dissappear?

If the sound changes pitch with engine RPMs, then fan and shroud are suspects, and they're easy to investigate. With engine set on high idle, grab the shroud and sort of muscle it around. Should be able to rule it out or nail it as being the culprit. Hope it's the latter, 'cuz that's easy to fix.
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EVfun
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PostPosted: Sat Apr 10, 2021 3:22 pm    Post subject: Re: Sudden new engine sound help Reply with quote

I got a chance to replace the exhaust tips so sounds were not drowned out by the pea shooter on the right side. Its guts were rattling around inside making enough noise up close that I couldn't pick anything else out. I got some new stainless pea shooters from CIP1 and they sound nice. Not much "freem" but quiet with just a light exhaust note in that higher frequency range. With that, and better light, the tacky exhaust leak took seconds to find.
Image may have been reduced in size. Click image to view fullscreen.

That leaves with with 1 "new" (not likely, now I can pick it out) sound of concern. It sounds a lot like lightly tapping a knuckle on a countertop. It seems more likely at idle or as the engine is losing rpm. It is almost random and sometimes may be twice back to back, or may not happen for several seconds. It is not crank end play, that's about 6 thou. Could it be camshaft end play in a 36 horse?

When I grabbed my phone I accidentally shot this picture of the '66 Pigalle seats in my '57 oval. Included just for fun.
Image may have been reduced in size. Click image to view fullscreen.

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66brm
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PostPosted: Sat Apr 10, 2021 3:36 pm    Post subject: Re: Sudden new engine sound help Reply with quote

Get the exhaust leaks sorted then listen again, I'm betting you are hearing decell backfiring due to the leaks
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PostPosted: Sun Apr 11, 2021 3:56 am    Post subject: Re: Sudden new engine sound help Reply with quote

Release bearing? How much peddle free play do you have?
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EVfun
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PostPosted: Tue Apr 13, 2021 3:20 pm    Post subject: Re: Sudden new engine sound help Reply with quote

Since changing a j-tube on a stale air heat engine is a bit involved I wrapped the leak loosely in fiberglass and managed to get a decent recording from the drivers seat. It was pretty loud this morning. Here is a link to a less than 20 second video where the metallic tapping can be heard coming and going. Pushing in the clutch doesn't seem to effect the sound, maybe a slight reduction.

[underlined link]
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Last edited by EVfun on Wed Apr 14, 2021 4:19 am; edited 1 time in total
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66brm
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PostPosted: Tue Apr 13, 2021 3:49 pm    Post subject: Re: Sudden new engine sound help Reply with quote

Have you checked with the generator disconnected? While the belts off check the fan, pulley and bearings
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EVfun
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PostPosted: Tue Apr 13, 2021 5:26 pm    Post subject: Re: Sudden new engine sound help Reply with quote

66brm wrote:
Have you checked with the generator disconnected? While the belts off check the fan, pulley and bearings

Thank you for the test. Unfortunately, removing the fan belt results in no change in engine racket. That tap-tap-tap continues, and like before it doesn't happen in all conditions. It seems to show up for idle, when the engine rpm is declining, and at higher rpms with light load.

I supposed I could just run it and let her blow, but it seems a shame to do that to a Feb. 1957 36 horse engine. It runs pretty strong (as it I think I can match the Road and Track test results of 0-60 mph on 42 seconds.) If I can't fix that sound I don't think it will run long!
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66brm
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PostPosted: Tue Apr 13, 2021 11:40 pm    Post subject: Re: Sudden new engine sound help Reply with quote

Might be time to pull the engine and have a look, check end play
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mukluk
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PostPosted: Wed Apr 14, 2021 12:27 am    Post subject: Re: Sudden new engine sound help Reply with quote

Are you certain the noise is coming from the engine? It sounds like it could be something else loose that's responding to the vibration of the running engine, say, maybe the shifter rod, coupler, or a loose transaxle mount.
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PostPosted: Wed Apr 14, 2021 5:15 am    Post subject: Re: Sudden new engine sound help Reply with quote

Unfortunately it sounds like a loose flywheel.
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PostPosted: Wed Apr 14, 2021 6:15 am    Post subject: Re: Sudden new engine sound help Reply with quote

I'm with Raydog on this one! Sad

Fix it NOW!
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EVfun
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PostPosted: Wed Apr 14, 2021 6:52 pm    Post subject: Re: Sudden new engine sound help Reply with quote

The old Bug is off the road! I have other priorities so I suspect it will remain off the road until this winter. As I fixed the other 2 sounds, and as this sound grew louder, I suspected it was a loose flywheel -- it was the best sound match (but still quite different) to the loose flywheel recording from Muir. I linked to his sound recordings above. I've never experienced that one before so I want to thank "raydog" and "oprn."

Since this thing already has the '66 Pigalle interior and a 40 horse gearbox perhaps the best use of it is to update it and drive it. It already has a well done color change from diamond green to black by an earlier owner (well done meaning the repaint includes the trunk, engine compartment, and interior.) Maybe I should update the engine and go 12 volt and toss in some old school custom with wheels, T-bars in place of bumpers, and a mild front lowering. Not necessarily a fast old Bug but a driver updated in looks and drive train with some Cal-look attitude.
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