You didnt say what kind of vac you have. Grating noises are often caused by the motor bearings being worn out. On most pull along models (once you have got the plastic casing open) the motor housing can be removed and the motor can be dissmantled quite easily. It is worth switching the vac on once the plastic casing is open to confirm if the noise is indeed coming from the motor. There are a few screws and or circlips holding the motor together and on some models the cowel has to be (gently) prized off with a screwdriver. You dont always need a new motor, as bearings can be ordered online (google the suppliers) There are two sets, one at either side of the motor shaft. It may only be the top set that is worn (This set is subject to more dust and grit), however for the price of them its worth replacing both. Most bearings have the item code printed on them. The most difficult job is in fact the first one; opening the plastic casing! Depending on model the screws can be one way and hidden under the rubber cover seal.
Andrew P. Hungary, January 2010
