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Mon Jan 12, 2015 7:24 am

On my way to work this morning, I noticed my bug was making a different sound than usual...and since I'm at work, I won't have time to look at it until later today if lucky, or later in the week if I get busy.

For starters, it's a 69 with a 1641 engine. Here's what I experienced this morning on the drive. At idle, the engine sounds slightly different, but barely perceptable. When I get going, I begin to hear a helicopter type sound coming from the rear, with peak sound around 1500-2000 rpm. Since I didn't get too fast on the way to work, I was only in 1st and 2nd, and it made the same sounds in both gears. Also, when I parked, I checked to see if it still made the sound when the clutch was in and it continued making the strange sound...so I'd assume it wouldn't be anything with the trans?

I'm guessing maybe an exhaust leak? A hole in the pipe somewhere making a rythmic thudding sound? Any ideas?

Thanks for the help!

Mon Jan 12, 2015 7:36 am

First thing I'd look at are your tires, a slipped belt, a Bubble, missing tread...... Even a Flat!

Dave

Mon Jan 12, 2015 7:37 am

Doubt it would be the tires...I still makes the sound when stopped and revving the engine...could be the belt though I suppose, would love for it to be an easy fix like that.

Mon Jan 12, 2015 8:13 am

Classic description of holey muffler or possible loose cylinder head bolts - that is more of a popping sound though.

Tire noise ruled out by noise present when stopped.

Mon Jan 12, 2015 10:23 am

I had the same thing happen once. Kind of a "whop, whop, whop" sound.
It turned out that it actually was a helicopter overhead.

Mon Jan 12, 2015 10:32 am

Had time to take it out for another spin quick to better focus on what it was doing, and here's a bit more detailed account.

Again, it will make the sound, but only just noticable when stopped and out of gear. The sound is very noticable when driving it and it seems to be dependent on engine speed while in gear driving.

So with that being the case, I think I can for sure rule out tires, and maybe even the belt since I can barely percieve it while stopped and revving...maybe when I "heard" it this morning revving it was just my imagination.

So at this point, the muffler/exhaust hole idea may not even hold water since it appears to be tied to my car moving and in gear. I tried coasting in neutral and revving a bit but did not notice the sound like when it was in gear.

Hopefully that makes sense...

Mon Jan 12, 2015 10:51 am

Throwout bearing? Sounds related to the trans? Is the trans covered in oil? Might it be leaking?
I've heard people describing thumping sounds related to the CV joints too? Might wanna check those to see if some bolts are loose/missing. It'll be gnarley when it finally fails!

Mon Jan 12, 2015 11:07 am

ROCKOROD71 wrote: Throwout bearing? Sounds related to the trans? Is the trans covered in oil? Might it be leaking?
I've heard people describing thumping sounds related to the CV joints too? Might wanna check those to see if some bolts are loose/missing. It'll be gnarley when it finally fails!

When I have different clothes on, I'll crawl under and see how the trans looks. Wouldn't the CV joints still make the sound when coasting in neutral though?

On a side note, I checked the oil when I took my lunch break and noticed the oil is milky looking... like water had somehow gotten in. With most of my driving being 1-2 miles, I know the engine doesn't get warmed up like it should, but could this be a contributing factor to the sound? Last week we had colder than typical temps, so I'm guessing some extra condensation had led to the large amount of water in my oil...

This keeps looking worse and worse.

Mon Jan 12, 2015 12:14 pm

Wxman2000 wrote: ROCKOROD71 wrote: Throwout bearing? Sounds related to the trans? Is the trans covered in oil? Might it be leaking?
I've heard people describing thumping sounds related to the CV joints too? Might wanna check those to see if some bolts are loose/missing. It'll be gnarley when it finally fails!

When I have different clothes on, I'll crawl under and see how the trans looks. Wouldn't the CV joints still make the sound when coasting in neutral though?

On a side note, I checked the oil when I took my lunch break and noticed the oil is milky looking... like water had somehow gotten in. With most of my driving being 1-2 miles, I know the engine doesn't get warmed up like it should, but could this be a contributing factor to the sound? Last week we had colder than typical temps, so I'm guessing some extra condensation had led to the large amount of water in my oil...

This keeps looking worse and worse.

I know I keep adding things, but here's some more. On my way back to work from lunch, I took it out on the highway to get it good and warmed up. While driving, it seemed like a lack of power...similar to when I had the 009 dizzy where it would bog a bit.

Also, there was no heat coming through the driver side vent, so there must be something going on with the exhaust even if it is unrelated to this problem.

When I arrived to work, I checked the oil, and it looks like I was able to burn out the water as it looked normal once again. Still making the thumping/thudding noise as originally though.

It makes sense how an exhaust leak could make the thudding noise, but could this also be the culprit to the power loss/bogging I experienced?

Mon Jan 12, 2015 12:22 pm

Loose Heads?

No power
Noise with RPM variation
Cold Exhaust

Mon Jan 12, 2015 12:24 pm

You can rule out CV joints because it makes the noise when stopped. Does the noise change when you clutch in/out while stopped?

Mon Jan 12, 2015 12:32 pm

Abscate wrote: You can rule out CV joints because it makes the noise when stopped. Does the noise change when you clutch in/out while stopped?

Clutch in/out does not change the noise, though again, when stopped and revving, the noise isn't nearly as noticable as when moving and in gear.

From what I could tell, it is most noticable when changing gears and through about 5mph into the gear, so like 15-20 or so in second gear, 30-40 in 3rd gear, etc. As I get "further into" each gear, the sound diminishes...or perhaps is just masked by the increased engine noise.

Mon Jan 12, 2015 12:34 pm

djkeev wrote: Loose Heads?

No power
Noise with RPM variation
Cold Exhaust

The exhaust isn't cold, just the air through the drivers side vent (probably a bad heat tube or something). Passenger side vent still puts out hot air, and the muffler was hot when I checked the oil after the drive.

Mon Jan 12, 2015 12:42 pm

Most of your driving is 1-2 miles? Buy a bike. My guess is your crankshaft end-play is excessive cos your bearings or case are shagged.

Mon Jan 12, 2015 2:20 pm

Firewall insulation loose and getting sucked into fan opening?
Rag sucked in?

Mon Jan 12, 2015 2:31 pm

I think Dave nailed it with loose heads.

Mon Jan 12, 2015 2:40 pm

Seriously, check your end play there horse. Give it a good rogering in and out. I'd say it's your crank or bearings there, badly worn and the clutch action is kicking the crankshaft in and out and the whole thing is battering around under load, but probably gets quieter when you step off the gas, or when you're in neutral with little to no load.

If it was loose heads or something in the fan he'd hear it equally loud when revving it in neutral.

Mon Jan 12, 2015 3:19 pm

If it's less of a heavy thumping and more of a knocking then maybe you've spun a rod bearing - pull one plug wire at a time off the distrib while it's running and knocking or banging or helicoptering and if the sound goes away on one wire then you know what cylinder it is, then you can go and have a look at the valves and see if there's anything major wrong with the valves for that ncylinder. If not, drain the oil and look for silver bits. Tell us what you find.

Mon Jan 12, 2015 3:39 pm

djkeev wrote: Loose Heads?

No power
Noise with RPM variation
Cold Exhaust

This sounds very reasonable.

Try taking 2 rags and block off the pea shooters when its running. If it holds lots of pressure, might not be an exhaust leak

Mon Jan 12, 2015 8:02 pm

Odd noise that varies with engine rpm, lacking power, and lacking heat on the driver's side... I'm thinking #3 cylinder isn't firing. First thing I'd check for is a loose sparkplug on #3, followed by ensuring the valves on that cylinder are properly opening and closing.