Annoying knock

[Peetee]

When the engine is on tickover I hear an annoying knock. It seems to dissapear as the revs rise and I suspect it is the LCB manifold rattling against the bulkhead aperture. It's not easy to see that area as it is on the inner lip so can anyone suggest a temporary way of moving/tilting the engine towards the passenger side a bit whilst still allowing me to run the engine to check? Just a half inch or so would do.

[Declan_Burns]

If the exhaust is rattling against the aperture you can fit an adjustable bracket similar to the one I fitted as in the photo below. It is bolted to the backplate.[frame][/frame]

[Peetee]

If only it were that easy. Its a 3 into 1 system, oversized for the 1275 engine so it's pretty reluctant to be adjusted to suit.

[chrisryder]

have you considered replacing the front engine mount rubbers? fresh ones could raise the engine up enough if your current ones have sagged.

[Peetee]

Thanks, but they are brand new.
Had a good shufty now and found the exhaust is not the culprit. It's coming from deep in te bowels of the engine. it's very obvious on tickover and less pronounced as the revs rise. Depressing the clutch definitely reduces the noise. I'm thinking the worst. Whats the general consensus?

[stephenpolhill]

Sounds familiar . Although mine only knocked when accelerating...

[bmcecosse]

How is the hot oil pressure?

[Peetee]

No pressure guage fitted but no illuminated oil light either.

[C6Dave]

No pressure guage fitted but no illuminated oil light either.

You need to put a temporay guage in to check the pressure.

It's no good relying on a warning light as by the time that comes on (if it's even working) you could have serious damage

[Peetee]

OK. So what do these temporary guages look like and where do i connect it?

[bmcecosse]

Best just buy a full time gauge - it's the MOST important accessory for any minor - way head of anything else......... Connects via a T piece where the oil pressure switch is fitted at the moment.

[twincamman]

If the noise goes away when you depress the clutch, I'd start looking at the gearbox. Obviously I haven't witnessed the noise, but it sounds like your mainshaft/layshaft bearings could be the problem.

[Peetee]

it sounds like your mainshaft/layshaft bearings could be the problem

I do hope so. I have a couple of spare boxes but no spare modified 1275 !
If it was the prob you mentioned would you expect the noise to be significantly improved whilst in gear? I'm not aware of the noise at all whilst driving - but then, with modified engine and exhaust, it's not exactly hushed.

[twincamman]

it sounds like your mainshaft/layshaft bearings could be the problem

I do hope so. I have a couple of spare boxes but no spare modified 1275 !
If it was the prob you mentioned would you expect the noise to be significantly improved whilst in gear? I'm not aware of the noise at all whilst driving - but then, with modified engine and exhaust, it's not exactly hushed.

It may well improve when in gear and under load as other noises will drown out the bearings. If you've got a spare box, then swapping it will only cost you time, and assuming the spare box is good, then that should prove or disprove my theory.

[Neil MG]

Clutch in reducing the noise does not necessarily point at the gearbox. Pressing the clutch puts some end load on the crank and that might be reducing the noise.

[Peetee]

Pressing the clutch puts some end load on the crank and that might be reducing the noise.

The noise of ...............?????

[Neil MG]

Thrusts? Mains? Big ends? Can't really even make an educated guess without hearing the noise...

[bmcecosse]

It will suppress timing chain clatter - as it moves the crank forwards and puts the chain under slight side loading. Could also be that the bronze bush in the tail of the crank is worn/missing and the gearbox shaft is not supported. Really hard to say without hearing the noise......

[Peetee]

As for possible cause, I believe it has come about as a result of a slight mishap involving an un-removed spanner on a pully nut that rapidly came into rapid contact with bodywork when the starter was turned.
Does that make it any clearer?

[Neil MG]

Loose pulley? Bent fan? If the fan is bent out of balance you will get a lot of vibration and strange noises! Or if it's bent far enough to touch something it will make even more. Dent in the timing cover? That might also cause fouling and lots of noise. Otherwise the errant spanner can't have done any damage inside the engine or gearbox!

Have a good look and report back...