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MG MG Y Type - bad vibrations

Finally Y5888 has it's APK (=MOT), after first failing on the missing makersstamp on the licence/numberplate (*#@%!).....

I bought Y5888 in June but "domnestic priorities", holidays, problems with old tyres, leaking exhaustflange gasket (it took hours to scrape of the old rusted gasket with the exhaust and manifold more or less in situ), leaking brakeline coupling, unclear chassisnumber, unwilling dynamo/regulator/rear lights/carburettor etc. prevented earlier MOT, so now I am very happy.

It's a shame that the weather isn't helping to clock up some miles, but in the miles driven I already noticed a rather bad vibration in the driveline/engine(?). I suspect the enginemountings or -steadybars, but don't really know what to look for.

Any suggestions?

Willem
Willem van der Veer

Fist check the universal joints at each end of the propellor shaft, these are the most likely culprits. It only takes a tiny bit of waer for the shaft to run out of true. An easy way to check is to put the car out of gear and 'coast' along when the vibration occurs. If it goes away you need to suspect gearbox bearings or an out of balance clutch.

Such vibration can ruin the rubbers on the engine steadt bar, this is a symptom not a cause, so if they are ruined find out why.

The rear anchor-bolt under the gearbox, that holds the gearbox down onto the cross-member, can break. The little rubber washers can also rot away due to oil contamintation. There is a good picture of this in the workshop manual. Sometimes the bolt breaks away taking a lump of the gearbox casting with it, my booklet on the gearbox shows a repair for this.

A common fault is the incorrect assembly of the prop-shaft. People do not realise that BOTH universal joints must be in-line, and not off-set. The shaft has to work at an angle and if the joints are out of line, the shaft has to run untrue to cope. This causes vibration and ruins the joints. The shaft comes appart at the splined sliding joint at the forward end, alas there is no master-spline.

Also, if the shaft has been removed and refitted, but not in the same bolt holes on the diff-flange, it can run out of true. The trick here is to undo the bolts and rotate it 180 degrees. An old cure for a shaft out of true, but with no obvious faults, is to fit two large Jubille-clips ait the centre, and move them appart by about 1/4" until the vibration ceases. You are crudely balancing it.

Gearbox rubber mounts are easy to replace with the cover removed.

Neil.
Neil Cairns

Willem - Congratulations on finally hitting the road! My car, Y5095, suffers from what sounds like the same vibration problem, and I have yet to find the cause. I have had the universal joints replaced and the entire shaft balanced, but that didn't fix it. Is it speed dependent? My vibration starts at about 30-35 mph and is prsent at all higher speeds. Sometimes the road surface seems to affect it, but not always, and on rare occasions, it doesn't happen. There was one occasion where I drove to town for something, about 10 miles, and she ran as smooth as glass. When I came out of the store to go home, not 15 minutes later, the vibration was back. Very frustrating!
Paul Briggs

Another thought has occured, are your wheels running true? Are the tyres sitting in the wheel rim square? You might have a slightly buckled wheel, or a tyre tread that 'writhes' as it rolls along.

A rare fault is an out of balance clutch, but this is engine-speed dependant, and quite violent at times.

Neil.
Neil Cairns

Neil,

How can a clutch be (or get) out of balance? My cluth judders on take off (hopefully badly adjusted clutch fingers but probably a leaking rear engine oil seal, we'll cross that bridge when we get there).

The reason why I suspected the steady-bars is that in the article "know your Y" they warn that "unless the steadybar is correctly adjusted the engine will vibrate badly"

http://www.mgcars.org.uk/mgccy/pdf/modernmotor.pdfe
Willem van der Veer

The correct hyperlink is http:www.mgcars.co.uk/mgccy/modernmotor.pdf I think!

Paul
Paul Barrow

This thread was discussed between 26/11/2003 and 28/11/2003

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