Loose Crankshaft Pulley?

It is not unusual for owners to notice a growing rattling noise from the front of the engine. If all is well with the timing chain and its tensioner, the chances are that the noise is coming from the crank pulley. It is equally common for owners to assume that the noise is happening because the pulley has worked loose. However, when they check the dognut it is fully tight. It is actually quite unusual for this nut to come loose.

In fact, the noise happens because of the stretching of the rivets that hold the two halves of the pulley together. The answer is to remove the pulley and re-tighten the rivets. However, that will probably only provide a short-term fix, so the pulley halves can be welded together or re-assembled with machine screws. The latter should be fixed with Loctite or, better still, wired together.

An alternative is to fit a later MGB harmonic balancer pulley, with the matching timing cover. This brings the additional benefit of the lip-type oil-seal that is far superior to the original felt ring.

To remove the pulley with the engine in situ, the radiator has to come out. The engine mounts need to be undone on top so that the engine can be jacked up to get clearance above the front lower cross-member. It is best to disconnect the accelerator linkage at the rear of the carburettor and ensure that no other connections are being stressed with the engine raised. The lock washer has to be freed off. Then you will need a long-reach socket extension and probably a long bar on the handle to get enough torsion to unscrew the nut. If it refuses to budge, it can sometimes be freed by positioning the bar against the floor and spinning the engine briefly on the starter. If the pulley is tight on the shaft, it can usually be edged forward using appropriate matching levers on opposite sides to keep the movement even.

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