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MG Midget and Sprite Technical - Midget 1500 engine rattle

Any ideas on what could be causing an annoying engine rattle on a recently acquired 1500 midget?

It is not there all the time, but comes under load - worse when hot and seems to go when you back off the throttle. Noise is metallic and rather tinny . .

Also noticeable if you rev at idle - it comes when you lift off. If you turn the engine off it rattles as the engine slows. .

Timing chain has been mentioned, but shells also (as these engine are prone to them failing)??

Oil pressure good when cold but drops to round 30-40 and 20 ish at idle.
C Burley

Check your engine mounts. The mounts on the 1500 are easily damaged, and can allow the engine to slump to one side or the other and touch things. It sounds like the noise only occurs when you back off, so perhaps the engine is twisting and contacting something.

Take a look all around your engine and see if any engine component is unusually close to surrounding structure, too.

On the off chance that this is an internal noise, you may be hearing the results of a failed crankshaft thrust washer. If this is the case, deal with it right away, since it can cause a loud and expensive engine failure if neglected.

Whatever the case, you might be able to localize the noise by revving the engine by rotating the throttle linkage manually and listening for noises with your head under the bonnet.

Best of luck! There are several of us here with 1500s, and we've seen it all. Sigh...

-:G:-
Gryf Ketcherside

If failed cranshaft thrust washer, then noise would be worse when clutch pressed?

You can get metallic-sounding noises from blowing ex manifold and gasket.

Big ends are easy to check by dropping sump; easy to replace too (make sure you get the right size). If high-mileage (or unknown) engine, replacing the b/e and thrust washers with engine in situ is a good insurance policy, given the history of these engines.

2 hours should do it, incl a cuppa!

A
Anthony Cutler

exhaust manifold gasket??
Nigel Atkins

Ignition timing?
Dave Rhine ('78 1500)

Condenser?

Sorry...

;-)

-:G:-
Gryf Ketcherside

It sounds like it might be pinking which should just need some adjustment, what colour are your plugs, has the car been tuned recently?

Good luck Carl
C Bintcliffe

Thanks for replies;

I took the fan belt off to isolate alternator and waterpump. Noise still present.

Sounds as if possibly coming from timing chain area, could the chain wear and be the cause of the noise?

Other than noise runs fine, does not overheat and pulls well through the gears. .
C Burley

Hi,
Approx 3yrs ago I had a strange metallic rattle from the engine of my 78 Midget 1500 and my first thoughts were that it was a loose 'tappet' - silly me!!!! I couldn't pin it down! However I had an occassion to visit my local mg spares supplier for some parts that I had ordered and as I drove into the fore-court of their premises and got out of the car a passing'mechanic' remarked " that has got to be the noisiest timing chain that I've heard in a long time!". He was spot on! They were also resposible for the replacement! I was impressed.
Bill.
W Wood

It helps to use a "mechanics stethoscope". A long screwdriver or metal rod with one end to your ear - or better, against the bony bit just behind your ear, and then touch the other to various (stationary!) bits of engine - block, timing cover, rocker cover etc. Or get the proper stethoscope - I got a real cheapo off a market stall for about £1.99 but it works well. Either is good for isolating engine noises.

But from what you describe I would suggest piston slap - which may not be what you want to know! See what Deborah has to say - she's the real expert!

Guy
Guy Weller

I have a tinny rattle in my 1500. I know where it comes from though and it's nothing critical. Mine comes from the carb pre-heater. It's that little device in the air intake line that looks like a blow-dryer....It has a spring operated flap in it to allow more air when warm. Well, the spring is no good and that little flap rattles up a storm when I idle too low or am shutting down....

Paul
Paul W 1976 1500

Paul -

That pre-heater was only fitted to US-spec 1500s. The home market cars had twin SU carbs, and a more conventional intake system.

And yes, mine rattles too. Argh... I was able to muffle it a bit by sticking some foam tape along the inside edge of the valve opening.

Cheers,

-:G:-
Gryf Ketcherside

Taken for MOT today - noise still there, and I am bemused as to whether it is indeed the timing chain or shells/bearings . . but although oil pressure drops when warm it is still 40-50 under load.
C Burley

popped down to see Chris this evening after work, I know naff-all about 1500s but it sounds like timing chain to me. Front of engine, definite 'jangly-rattle' not pinking or popping or blowing.
David Smith

This thread was discussed between 11/08/2010 and 08/09/2010

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