Resonance

[daren007]

My 30 A five window coupe (I gave that info because it may or may not be revenant) has a resonance at about 1200 rpm/25 mph that is similar to driving your car with the back windows down. It is loud and uncomfortable. Makes conversation difficult. It is a kind of buffeting you can feel in your ears. Help! Any help!

[WHN]

Need more info.

If car is not moving how does the engine sound? Also, did it just one day start making this noise?

What is general condition of car?

[Marshall V. Daut]

Does your coupe have an interior? Ones without interiors are like driving in a tunnel. I usually put some kind of sound deadener behind the interior panels and that helps a great deal.
Marshall

[wingski]

Daren, check your exhaust system. If you have any place on that tailpipe, muffler, or exhaust pipe that isn’t supported by flexible, rubber supports, the vibration will carry to the frame. Even if everything seem Ok, it’s possible that with weight in the car something is touching metal. The exhaust systems on my XKE Jaguars were supported by springs, and they would resonate at 3200 rpm. It was a wonderful sound, but on a model A, I don’t think it would be pleasant at all.

Mike

[daren007]

The car is in very good condition. The interior is real nice. I can get this sound with the car in neutral by just revving the engine. The exhaust is sound (no pun intended). I know that if you modify the exhaust on cars/trucks you can get this annoying affect The muffler is a tapered unit although somewhat noisy. Perhaps the insides are deteriorating.

[WHN]

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Disconnect exhaust. When I was younger we did all the time.

If your problem sound is gone. Job well done.

You might like how a Model A sounds without exhaust. Enjoy.

[Tom Endy]

if you have engine splash pans installed, check to see if the mounting taps that attach to the engine have broken. They are prone to breaking due to vibration and will create a loud noise, especially during deceleration.

Tom Endy

[Jacksonlll]

Make sure you have clearance to the exhaust pipe as it makes it's first bend after the manifold. Contact there would make a lot of noise.

[daren007]

Engine pans...Hmmmmmmmmmm. I have considered disconnecting the exhaust just to see. The engine has been through a major overhaul and I do not recall if the problem was there prior. I only had the car a short time with other issues before pulling the engine.

[Tacoma Bob]

MMMMM Might want to check the fan blades and hub for cracks. Look very carefully as the little buggers (cracks) can be hard to see. Sound waves can telegraph.

[Jacksonlll]

Be super careful with that fan. If it comes apart it can hurt you. Be sure it is tight to the pump shaft.

[1crosscut]

Very often the sound you describe comes from the exhaust pipe vibrating like others have stated earlier. There is a bracket that holds the tail pipe loosely and it will create quite a racket. To make sure that it isn't the source of your noise take a piece of shim stock or something similar and wedge it in between the tail pipe and bracket to see if that cures it. Be sure to remove it after you are done testing.

[Y-Blockhead]

Originally Posted by Tom Endy

if you have engine splash pans installed, check to see if the mounting taps that attach to the engine have broken. They are prone to breaking due to vibration and will create a loud noise, especially during deceleration.

Tom Endy

Boy ain't that the truth. It about drove me nuts (nuttier?) trying to find a noise. Turned out to be a broken tab on the engine pan as Tom suggests.

[daren007]

More ideas. Thanks.

[Synchro909]

As I read the OP, my first thought was "Exhaust clamp!" but when he mentioned hurting ears, I wondered whether winding up the window would help. Travelling with window down can cause a hell of a buffet. If that is the case, wind wings/deflector would probably be the answer.
If it is nothing to do with an open window, maybe have someone stand on the side of the road while you drive by in 1st gear with the vibration happening and see if they can pick at least which part of the car is the source. Maybe even someone driving alongside with their window down.
It's a difficult task to track down a vibration like that even if you are there. More difficult from here!

[SeaSlugs]

could be floor boards not sitting flat or somehting in the trunk/rumble not sitting quite right.

I know the noise your talking about. my 17 silverado does the same with the front windows down... jeep wranglers with a hard top are notorious for it as well. 18 tahoe i had as a loaner with the sunroof cracked made same annoying air buffering noise.

[J Franklin]

Have someone ride with stethoscope. Drive it with the fan belt off.

[daren007]

Windows up or down do not have an affect on it.

[TerryH]

I had a loud, terrible noise coming from my car, and I asked Tom Endy about what might be causing it, and it was 2 broken tabs for the engine pans. At certain speeds, it sets of a kind of resonance due to the vibration and makes a lot of racket. Easy to check just to make sure.....

[40 Deluxe]

NHV (noise, harshness, vibration) is still a problem on new vehicles and a lot of TSB's are issued to solve such complaints which can be hard to track down. Every engine has its own RPM range that sets up vibrations of one type or another. A collapsed motor mount or a replacement with harder rubber, sheet metal cracks, a broken bracket, slight engine or drivetrain imbalance, worn bearings, etc. can set things off. Happy hunting!

[Drive Shaft Dave]

A friend of mine with a 30 coupe had vibration at a certain rpm, it sounded to me that it was the wood around the rear window. Maybe worth checking.

[California Travieso]

Sychro99,

Your idea of having someone stand on the side of the road to listen for the noise reminded me of an old time mechanic when I was a kid. He used to ride on the running board to listen for noises! Not advisable these days but manybe a friend could open the door and lean out to listen for the noise.

David Serrano

[Y-Blockhead]

I recall a while back someone had loose radiator support rods that were causing an allusive noise.

[Big hammer]

Originally Posted by California Travieso

Sychro99,

Your idea of having someone stand on the side of the road to listen for the noise reminded me of an old time mechanic when I was a kid. He used to ride on the running board to listen for noises! Not advisable these days but manybe a friend could open the door and lean out to listen for the noise.

David Serrano

My dad put me out along a road to listen and look for a tire that was flapping
Middle child of five, I was wondering if he was going to come back and pick me up :-( he did :-)

[Jacksonlll]

Just a thought, those hood props can make a lot of noise if they are loose on the radiator support rods.

[BILL WILLIAMSON]

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I almost NEVER found Minervas' pesky rattle noise. It was a loose wood piece, behind the R/H quarter window. Punched a small hole & "injected" some Insulating Foam & QUIET!
Bill Lazy

[wingski]

Thanks guys, you’ve made my day by making me laugh. I’m surprised that nobody suggested insulting a bunch of kids on a street corner, and yelling out and asking if any of them heard a noise as they chased your car.

Mike

[BILL WILLIAMSON]

I "endured" a new rattle for 4 DAYS, until I discovered I didn't tighten one, (1) windshield adjusting KNOB---LOL
Bill Absentminded (I think my brain wuz absent, thet day???)

[Jacksonlll]

A rattle I finally found, ended up being a very loose gas tank clamp way under the dash rail.

[katy]

I can get this sound with the car in neutral by just revving the engine.

Check that the fan blades are all straight and even, and/or try running the engine w/the fan belt removed as suggested in post #17.