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Chicagoland MG Club: Driveline
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  Chicagoland MG Club:Driveline

Just a Simple Wrench
by Ann & Jake Snyder
Out of Warranty

Ann and Jake Snyder Someone who reads these pages once commented that more things happen to us (i.e. mechanical problems) than to anyone else they knew. Thats only logical- we probably drive our MGs more than anyone else they know. And, had our MGs come with ten year, 100,000 mile warranties, none of them would be still covered at this point. There is a reason for mileage and duration limits on warranties: parts wear out with use or deteriorate with age. Eventually even some parts that one would expect to be immune to failure, do just that. Almost all of our repairs are accomplished as preventive maintenance in the comfort of our own garage. Occasionally these repairs are prompted by visual, audible, tactile, and yes, even olfactory cues that the car graciously provides in advance of the actual failure of a part.

A rare exception to this usual scheme of things occurred just recently, courtesy of our 73 MGBGT. Its first request for attention came as we were driving as a caravan of two cars from Lake Bluff to Marengo, to put away the 74 1/2 BGT for the winter. When one of us driving the 73 heard a belt squeal, the conversation on the family radios was something like this: I just heard a belt squeal and smell hot rubber. Yes, Im sure its this car. The alternator light just went on, lets pull over. One fan belt replacement on the roadside, no problems, except that the probable cause was frozen bearings in the air pump. So thats why the car had been a little slow cranking, a recent phenomenon that we had attributed to the colder mornings. Well, not entirely...

The next week the car still did not crank as well as it might, and one evening we noticed that the headlamps were not their usual halogen brightness and that the turn signals were very slow. Sure enough, after stopping for petrol, we had to push the car to get it started. Upon returning home, we checked the fan belt. The spare that we had used the previous weekend was a used belt, and it had stretched. We put on a new belt and set the battery charger on the 2 amp automatic setting overnight. In all probability, this should have solved the problem. Well, not entirely...

The car still did not crank well, and over the next few days we began to suspect that the starter was at fault. One day after work, it would not crank enough to start the car. The battery did not seem to be at fault, because the headlamps were bright and did not dim during the attempts to start the car, and the turn signal frequency was normal. Another push start enabled us to get the car home, and that evening we replaced the starter with a used spare. Is this the end of the story? Well, not entirely...

The following evening after work, the car started fine- but immediately revved up to about 4000 rpm. Everything under the bonnet seemed fine, except for the throttle cable- it was frozen within its sheath. We always carry a spare. It is the part that we have most frequently loaned to others (even more frequently than a fuel pump). So we changed the cable and got to Natter n Noggin only 15 minutes later than usual. Problems come in threes, and we had replaced a fan belt, a starter, and a throttle cable in just over a week. But the throttle cable still left us with an uneasy feeling, and when we returned home that evening we visually checked that the engine ground strap was in place.

engine ground strap and fractured bolt
Grounding strap and snapped bolt. Note the reflection from the shiny surface of the fitting on the left and the dull surface of the fitting on the right.

The following morning the car barely cranked at all. After repeated attempts to start the car, a wisp of smoke was seen escaping from under the bonnet at the rear of the engine bay. Oops! Key off and fire extinguisher ready before opening the bonnet! All appeared well- whatever had been smoking was smoking no longer. The battery charger was put into use again, this time to start the car. But something was very strange- the throttle pedal would not move. So we have finally reached the conclusion of this shaggy dog story. Later that day, the ground strap was replaced with a heavy-duty version from the local NAPA store, and the car has run perfectly ever since. The reason for this ground strap is that the drive train is electrically isolated from the chassis by various rubber mounts. Without a functional ground strap, another path to ground will be established, and this usually involves the brake lines, the fuel line, or (you guessed it) the throttle cable. This bad ground had been the source of all of our problems except the fan belt. The headlamps have their own ground, and thus, when the battery had not been drained, functioned perfectly even when the starter would not crank.

When we removed the old ground strap, we found a few frayed strands. More telling, we think, was the fact that during the removal, one of the mounting bolts snapped off with a mere 3/8 inch drive socket. This bolt is actually one of the engine mount bolts and is a stressed part. Examining the fittings on the ends of the strap, we found the surface on one end to be shiny, indicating that it had been in tight contact with the bracket. But the surface of the other was dull. We suspect that, with time and wear, the bolt had stretched and the physical contact between the grounding strap and the chassis was no longer tight enough to provide a good or consistent electrical contact. We chose a new grade eight bolt to replace the broken one. It should last another quarter of a million miles before we need to replace it.


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