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MG MGA - Buzzing noise at about 1,500 r.p.m...


Hi everyone,
My 1600 Mk1 Roadster, no. 84647 ,is running well at present(touch wood)but nevertheless has a problem that is driving me up the wall !
At around 1500 r.p.m. there is a loud buzzing noise from the engine compartment.
My first impression when I heard it was that the fan blades were coming into contact with something.
However, inspection of the fan has not revealed any damage
or any indication that it is touching anything.
The other day I ran the engine with the bonnet up and juggled the pedal to maintain 1500 r.p.m. while someone stood beside the car to see if he could tell where the noise was coming from.
He said he thought it was from the left hand side of the engine bay.
Have any of you encountered something like this before ?
Any suggestions will be most welcome.
Season's greetings to all,

Ray.


RC Brown

Ray,

I have the same problem and am searching for a solution. I though it was the hood vibrating against the body but.....

This drives me CRAZY as I spen most of my time around that RPM as the speed limit is 30 km/h, or right about 1500 RPM.

I'm interested to see what plays out.

Tom
Tom Baker

Ray

I had a similar noise although mine was more prominent at about 2200RPM. Turned out to be worn innards in the starter motor bendix. I presume the disturbed air and/or vibration caused by the spinning flywheel made the assembly rattle. Sounded like a tinkle.

Steve
Steve Gyles

Ray,
I've had this sort of vibration from the carby overflow pipes touching the chassis. Check what they are near.

Mark
Mark Wellard

Ray, look closly at all the engine & trans mounts and exhaust system. Any thing from the drive train that may be touching the body can transmit noise you would not hear otherwise.
John H

Some years ago I had a buzzing noise when I upshifted through the gears. I finally found the problem. My after market pancake filters had inner wire mesh to keep the foam filters in place. At just the right RPM they would rattle (buzz) against the air filter cover.
I fixed the problem by glueing cork material on the inside of the cover. Then later switch to K & N filters.

Ray

Ray Ammeter

Check the Carburettor heat shield clearance from objects in the vacinity such as the overflow tubes.
BOL,
Doug
D Sjostrom

Check the hood release rod. It should have an anti-rattle spring attached to a friction eyelet on one end and the lip of the fresh air inlet mounting tube on the other. If the spring is loose or missing, the rod has a tendency to vibrate against the fender.

Steve
Steve Brandt

A further thought for you...
I had an annoying engine noise for ages on my "1600", sorry can't be specific about certain revs. After changing the dynamo and water pump I then found the crankshaft pulley was starting to fall apart as the rivets had gone all loose. That made a worrying noise, but once fixed, I still had something else up the front of the engine, the only thing left was the timing chain. So I had the timing chain, tensioner and sprockets replaced (when U/head fitted). The sprockets had become worn into slight "hooks" which can sort of pluck at the chain and cause it to slap the timing chain case. Am fairly certain this is what was happening, certainly annoying. All seems much better now. Now how do we shut those tappets up?
Good hunting!
Pete
Pete Tipping

I have it too. Replaced the hood bumpers, checked all lines and hardware and stil it buzzes! One day I'll figure it out... I hope!
Steve Simmons

I had a crank pully that was loose on the crank causing the key to wear a bit and cause a low rpm buzzing noise. A new key and thread lock fixed the problem.
John B

Ray

You could check the bonnet hinge mounting bolts. Also at various times I have had a buzzing sound caused by the inlet vents vibrating. One is still glued down with chewing gum after I finally nailed the problem on a long run on a very hot day.
Cameron
Cameron McIntosh

Identify the frequency of the vibration, then you will have an idea of the physical size of the offender. If it's a high buzz, it will be small. A deep sonorous buzz is something big. etc.

If you can identify the location roughly, then it's just a step by step process of elimination. It's not like a modern car where all is hidden behind some sort of cover - all is bare and accessible.

It may be better that YOU stand outside the car and listen. You will probably have a better idea what you are looking at / for. At least if it buzzes when standing still, you can rule out a lot, and use a stethoscope if necessary to nail the offender.
dominic clancy


Thanks,everyone,for your ideas.
You have given me some good leads...
Tom,I hope this has been a help to you too.
Cheers,
Ray.
RC Brown

Hi Ray

Check your bonnet hinges, I had a vibration which disappeared when the bonnet was up, at first I thought it was the hinge pins, it turned out to be the the curved parts of the hinges vibrating against the bulkhead, I could see where the paint had been rubbed away. As mentioned, the heatshield can also vibrate. Is it a bee ? No, its an 'A'

Terry
Terry Drinkwater

This may be off the mark but I had what I would describe as a "buzzing" noise coming from the left side of the engine bay as well. The noise would be sporadic. Sometimes there sometimes not. What it turned out to be was a noisy tach cable. Once it was located the noise was really up under the dash but somehow transferred thru the firewall to give the impression that it was coming from under the hood. I removed the inner cable, lubricated it and the noise disappeared. Likely not your problem but then again might be worth checking.
Michael Hosier


Thanks also,Terry and Michael.
I am pleased to be able to tell you all that the problem has been tracked down and rectified.
Despite seeming to originate in the LH side of the engine bay the noise was actually coming from the front and centre....
I had given up on finding the source of the noise and as the car had to go in to the mg specialists for one or two other things I decided to hand the problem of the noise over to them.
Turns out that the bonnet latch return spring , part no. ADA466,Moss no. 329-175 was touching the bonnet locking platform . Not a problem except,when the engine was turning over at between 1500 and 1600 r.p.m.when the spring rattled against the platform( or cross brace as I used to think of it.)
A little tweaking of the spring and a sheath of " spiral wrap " around it to make sure...
The worst part of it all was getting the grille and piping neatly back in place but then I hardly need to tell you guys about that...
Thanks again.
Ray.

RC Brown

This thread was discussed between 05/12/2005 and 10/12/2005

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