The MGA With An Attitude

At 12:58 PM 8/27/04 -0700, Ron Engelhardt wrote:
>" I've been hearing a light jangling noise from my engine (58 MGA 1500) for a short while. .... the crankshaft pulley is composed of two halves riveted around a central hub. The rivets have loosened ever so slightly allowing the two halves to jangle. .... Is it in danger of separating completely (doesn't look likely) or can I "grapes of wrath" it somehow until driving season slows down enough so I can get to it?"

The answers are yes, maybe, and if I was you I'd FIX IT IMMEDIATELY.
crankshaft pulley welded

The picture here shows one that had failed in the same manner. This is a fairly common failure. Once the rivets are loose enough that it makes noise that you can notice, the time left to total separation may be as little as a hour at highway speed. Attempting to reset the rivets will usually not hold for much longer after the holes in the flanges have started to wear larger. This one has the sheet steel pulley flanges MIG welded to the forged steel hub. Such welding or brazing is a good functional repair, as long as it is done early enough that the flanges are still concentric on the hub, and the pulley flanges still run true.

Unfortunately this particular pulley had to be retired because of slightly bent V-groove flanges. When the flanges are bent the groove will wobble and will vary in width as the pulley rotates. This will chew on the flanks of the belt to eventually wear it out, making it thinner and fraying the edges. The first sign of this type of belt wear may be a loose fan belt, accompanied by rising coolant temperature and/or failing charge in the battery. After retensioning the fan belt it may get loose again in just a few hours of running time. About the third time it gets loose you may run out of adjustment range on the tensioner bracket, or the belt may simply break by that time. If your fan belt will not stay tight or wears out prematurely, it's a good sign that the pulley flanges may be bent.

You might be able to straighten the flanges by fixturing the pulley in a lathe and pressing against the flanges with a roller as it rotates slowly. Otherwise straightening pulley flanges is exceedingly difficult, so you are likely better off replacing the pulley.

The same rivet failure problem can happen to a generator pulley, which is riveted in the same manner. But the MGA generator pulley has an aluminum hub with steel flanges, so it cannot be welded or brazed. One time in a pinch I managed to repair a generator pulley by replacing the rivets with #10-32 hardened steel machine screws and hex nuts. I then heated each screw in turn to glow a dull red, followed with an additional half turn of tightening, and allowing them to cool for a very tight shrink fit. This lasted for several weeks until I could procure a replacement part, but I wouldn't recommend running it forever in such condition.

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