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MG MGA - Strange Noise......

My MGA has a strange noise. It sounds like something rattling against something tubular like the exhaust or driveshaft making a 'ding-ding-ding' high pitched bell sound. It happens around 2800 rpm and it does not seem to change with the revs of the engine or with the speed of the car.

I have inspected the exhaust for loose bolts/hangars/brackets and rapped it with a soft faced hammer but can't replicate the sound. The area around the driveshaft seems free and clear as well.

At this point I have no way to raise the car to inspect so I am hoping one of you has had a similar issue.

Any ideas?

Thanks!

Tom Baker

Check the front pulley to ensure that the rivits are still holding everything tight. When these are loose it tends to make that kind of sound. Catastrophic failure if it goes un treated.
Robert (Bob) Midget Turbo

Hi Bob,

I have installed a supercharger and it has a solid front ribbed pulley. I wonder if it is working loose....

I'd hate to have a pulley failure kilometers from home!
Tom Baker

Have you installed any seatbelts lately? when I installed mine the bolt was sticking out enough were when I went over a bump it would touch the drive shaft and make the same noise.
WMR Bill

No new seatbelts, but I did have the driveshaft out recently to replace the rear gearbox seal (1500). You know, come to think of it, what if the dome shaped stamped press fit sheetmetal cover on the driveshaft has worked loose?? If so, short of welding it, what could I do? Could this pose a danger or an annoyance?

Thanks for helping me rack my brain!
Tom Baker

Tom, I had a similar problem a couple years ago. It turned out that a piece of the clutch plate had deteriorated and broken off. The car ran fine for about 50 miles until the rest of the clutch plate came apart. Hopefully this isn't your problem...Dennis
Dennis Suski

Tom

Sounds to me like a severe case of Gyles Bendixitus. I currently have a similar sound and have had it once before. It's a worn and partly jammed starter bendix - starter probably not returning to its fully at rest position. The bendix then starts rattling in the disturbed air of the fast spinning flywheel. Like your symptoms, my rattle starts above 2500rpm, and its resonance remains constant regardless of any higher RPM.

I discovered it by chance one day when I inadvertantly pulled the starter knob when the engine was at idle. The rattle I heard in amongst other whirring and teeth meshing (or not) noises zeroed me into the cause of the hitherto unknown tinkle.

Steve
Steve Gyles

Well, first of all, whenever you do figure it out, you need to post the answer. That being completely unhelpful, I will offer this. My dad had a similar problem and it turned out that one of the little springs in the clutch plate had fallen out and was bopping around free in the bell housing. It is too bad you can't post a WAV file on this page so we could hear the noise too.

Dennis, Arizona
rtoys

If it only rattle when moving, check the bell shaped dust cover on front end of the mid-1500 type propshaft. It is a press fit and may come loose sometimes. Just tap it back into place and add a couple of tack welds, like this: http://mgaguru.com/mgtech/propshaft/ps101.htm

If it rattles with engine running while standing still, try depressing the clutch. If that makes the noise go away, it's something inside the bell housing, which would require pulling the engine to fix. It might be the clutch release bearing rubbing on the gearbox input shaft, particularly if the release arm pivot bushing or pivot bolt were badly worn, or if the release bearing retaining clips were loose. It might be one of the three clothespin springs holding the release thrust ring to the pressure arms come loose, or one of the three arms gotten out of adjustment.

If you have an MGB diaphragm type pressure plate, the heavy steel thrust ring that accepts push from the release bearing might be loose. This piece is held in place by a thin steel eyelet that is prone to work loose after high mileage, but might otherwise come loose shortly after installation of a new clutch (if it was poor quality manufacture. When it rattles the clutch still works. When it stops rattling the broken fragments might break chunks out of the sides of the bell housing. BTDT:
http://chicagolandmgclub.com/photos/gearbox_reb

If it rattles while running but is not affected by the clutch action, then it's something on the engine but probably not inside the bell housing. Check for loose rivets in the generator pulley, or loose nut on front of generator allowing the generator fan to rattle on the shaft.

Check for rattle in the starter pinion Bendix drive. On the MGA you should be able to poke this with a stick behind the bell housing while engine is running (if you do not have a starter drive cover in place). If that stops the noise it would be a loose pinion gear, quite likely a broken clock spring in the Bendix drive. R&R the starter motor for that fix.

Check mounting of the exhaust pipe where is should be attached to one or two bell housing bolts with a short metal strap or two. If one of these straps should break (common for original issue type parts), the stub end hanging loose could vibrate and make a rattling noise that might have a fixed resonance frequency.

Check everything around the carburetor heat shield (if you still have one). Anything made of sheet metal and attached to the engine would be suspect. Ditto for any tension coil spring, like a throttle cable return spring for instance.

Thump hard on the exhaust system with your fist. Any loose metal part there (even inside the muffler) might rattle with engine running.

Some time ago I had a strange rattling noise with car in motion, accompanied by a light squeaking like a spastic mouse. That turned out to be the rear license plate bracket (large plate) being cracked and squeaking when it would vibrate.

Very recently, after last July completion of my MGA body restoration and reassembly, I had a loud vibration noise at 1100-1300 rpm engine speed, regardless of vehicle motion or throttle load. The noise sounded like perhaps some sheet metal loose behind the dash. It turned out to be the tail end of the engine bonnet was a tad too high on the hinges and not properly nested against the rubber buffers, so the bonnet was vibrating strongly at that one resonant frequency.

If it rattles when running and stationary with the bonnet open, start poking at everything in sight with a stick. If you can get the noise to stop by poking on something, you're getting very close to the problem.
Barney Gaylord

Hi Barney,

Many, many great points as usual. I am not willing to rule anything out at this point but you bring up some interesting scenarios.

I believe that it only happens while the car is moving. I have tried to recreate the sound while bringing the RPMs up slowly, the I tried revving up while the car is parked and I haven't heard it.

I recetly changed the rear gearbox seal so maybe while the driveshaft was out it was bumped or the cover just decided to work loose.

I worked the clutch several ways and found no difference. Of course I did this while in motion and with the ding-ding-ding. I also shut the ignition off, tugged on the emergency brake (thinking the cable over the exhaust was loose).

I did add an alternator but I had to change the pulley and cooling fan. Maybe the nut isn't tight enough. While I'm there I will also inspect the starter bendix.

I still have a carb heat shield and I did check that and found no cracks, loose spring, bolts, clips, etc. There is no way I would run without one of these with the deadly stop-and-go traffic around here.

I took my dead blow to the exhaust and worked it pretty good. I did check the straps, one in front by the bellhousing, one u-shaped one in the middle, ond the read one. All were amazingly OK.

I strongly feel that this would be a loose dust cover on the driveshaft. I won't have time to get it welded by Saturday, but I can easily remove it. If that turns out to be the problem, can I safely run the car for a couple of days without it?

Tonight I will check the bendix and alternator. If I can't find it, then I'll start poking around until I do. Hope it's not in the clutch area but if it turns out to be then....

The last annoying noise I had would pop up at 2000 rpm and buzz away. It sounded like the bonnet was vibrating against the bosy, as your did but pressing down on it did nothing. I finally tracked it down to the hood latch return spring vibrating against the u shaped support just in front of the radiator. Popped a thin piece of rubber between the two and the noise is gone!



Tom Baker

After all THAT I can only say 'Thank God I'm a bit DEAF!!!!!!!!
Barry
BM Gannon

Sorry? :)
Wim Betzel

Barry

My method is to put earplugs in and turn the radio up! That, combined with windblast, usually takes my mind off it.

Steve
Steve Gyles

I once tried Barney's stick poking method and got terrible results. I used it to try and locate and incessant and irrating noise in my house. After about an hour of poking, the stick landed on my wife. The noise got worse and my stick and I are now living in the garage.
James Johanski

Yes James, it can be dangerous. Very dangerous.
Tom Baker

Tom
I had a similar noise that I (eventually) tracked down to the alternator fan which was brushing against the body at certain speeds. This was the start of terminal bearing failure so I would check that also. Best is to slacken off the alternator/dynamo and give the shaft a wobble. If there is more than a slight movement this could be your issue.

Neil
Neil Purves

This thread was discussed between 05/04/2009 and 07/04/2009

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