Random Buzzing at Higher Revs

AKimball92

AKimball92

True Classic
My car seems to run great. There are definitely things I plan to work on to continuously improve it. One item that does bother me is a intermittent buzzing noise coming from behind and towards the passenger side. It sounds like it could be a relay clicking really fast. The sound comes in for a few seconds at a time even during the same high rpm acceleration. I can sort of recreate a similar noise by shifting into neutral. My car does have the neutral switch on the transmission with a wire almost loose. I am fairly certain the system doesn't feed anything else on the car. None of the relays on the fuel tank/spare tire wall are warm from over use after a good drive.

Another possibility would be something in the dizzy area? That at least is in the general direction of the noise as heard while driving. I have not heard it in the garage to place it. This weekend I will try to get the lady to help in locating the noise. Lets see how well she likes high revs in the garage...

I know vibrations are very hit and miss between different vehicles so I know this is a slim chance others have experienced the same exact issue.
 
I will have to sort through a fair amount of go pro footage and see if its audible. A lot of other noises came into the video that were not really prevalent while driving. I also think the camera was tapping against the back glass. <face palm>. High quality production right there.
 
If it happens at the same rpm then probably a section of sheet metal buzzing. I know that does not tell you much but look for any metal panels that are attached in a way they could vibrate.
 
I had a noise similar to what you described that turned out to be a rear brake shield. One of the metal mounting tabs had fatigued to the point where it was no longer connected to the shield other than by touch. At certain engine speeds it would resonate.
 
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AK, can you differentiate it as being either a electronic buzzing (e.g. signal noise) vs a mechanical vibration (e.g. loose item)? And you said it is RPM dependant, not speed dependant? So it is the same when at a stop vs driving on the road?
 
dllubin said:
I had a noise similar to what you described that turned out to be a rear brake shield. The one of the metal mounting tabs had fatigued to the point where it was no longer connected to the shield other than by touch. At certain engine speeds it would resonate.
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I will tap around this weekend and see if I notice anything loose.

carl said:
If it happens at the same rpm then probably a section of sheet metal buzzing. I know that does not tell you much but look for any metal panels that are attached in a way they could vibrate.
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I haven't been able to lock in an RPM. I don't know if that's just me not recording every RPM and plotting it on a bell curve yada yada yada. I just get the feeling its very intermittent. I would be driving at steady state and it could buzz on and off a couple times for only a few seconds at a time.

Dr.Jeff said:
AK, can you differentiate it as being either a electronic buzzing (e.g. signal noise) vs a mechanical vibration (e.g. loose item)? And you said it is RPM dependent, not speed dependent? So it is the same when at a stop vs driving on the road?
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My first thought is it's the physical sound of a relay opening and closing. The same sound you hear when you first power on the headlight motors. I also hear something very similar shifting into neutral; that's a singular click. The buzzing is that click just many times really fast. same pitch and sound frequency just maybe at 10-20 hz.
 
My crusty exhaust manifold heat shield likes to buzz between 4100 and 4300rpm. It's my X1/9's way of nagging me to fix it.
 
I have the exact issue that @kmead described and it makes me crazy... The quick simple solution was to use a zip-tie on the U-shaped spring hooks where they connect to the body. It holds them together and reduced the buzz by 80%... I still have the buzz but now it just sounds more raspy than annoying..
 
kmead said:
My exhaust mount springs make all manner of loud noises. I know your exhaust is custom but it might be an area to look into.
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Exhaust hangers sounds very plausible, I could certainly see how it's intermittent. I will purchase some safety wire and tighten all 3 up and see what noise changes. The distance from me, through the engine bay and muffler area could dull the sound to more of a click than what you would expect the metal spring rattle to be.

Cratecruncher said:
My crusty exhaust manifold heat shield likes to buzz between 4100 and 4300rpm. It's my X1/9's way of nagging me to fix it.
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I hand shaped a new shield due to the new manifold/intake combination not matching anything that I could find and know works. It's bolted and pretty tight in there. I don't think it's the cause but some ball-peen tap tapping might verify this.
 
I have had a vibration buzzing noise at 3000 rpm to 3500 for a few months. the sound resonated all around the top of the motor. I went as far as doing a valve adjustment because it sounded like it was coming from the cam box. I even thought maybe it was some internal damage to the motor. It was driving me crazy. Yesterday I put the rear up high in the air and started it to look again. The noise was a lot more pronounced. My alternator bottom mounting bolt was gone. It was held on by just the tension adjuster. New bolt and sound is gone. These vibration noises travel all around and are hard to locate. It's so much more enjoyable to drive now.
 
Maybe one of those mechanic stethoscopes would help to locate the source of the noise?

AK, any news on this issue?
 
Unfortunately I havent had a chance to drive the car in a while. Between my Mazda3 on jackstands in my 1 lane driveway and it seeming to rain on the weekends the car has stayed parked.

I might have found the culprit though. There is a plastic female thread clip on one of the engine bay shields to the wheel wells that was able to rattle. Given the irregularity of the buzzing noise this might be it. All it needed was the correct excitation and then could buzz for a few seconds.

Given winter is coming here soon in Michigan, this thread might be on hold until spring. :( Also, I am taking some classes through the winter and spring taking up much of my free time.
 
Are you referring to the plastic splash shields? Can't imagine that causing a buzz. So you must mean a different type of shield. Keep us posted when you get a chance to get back on it.
 
Dr.Jeff said:
Are you referring to the plastic splash shields? Can't imagine that causing a buzz. So you must mean a different type of shield. Keep us posted when you get a chance to get back on it.
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My new passenger side splash shield that protects the timing belt from the wheel well is metal. It has the plastic female threads clipped in. One clip is a tad loose and when tapping it with my finger creates about the same noise.

As long as its not dizzy or valve train related I'm not too worried.
 
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