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Chicagoland MG Club: Driveline
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  Chicagoland MG Club:Driveline
Just a Simple Wrench

by Ann & Jake Snyder

A Strange Cold Night

The weather was working its way around to the fall season in the Rust and Frost Belt, and the 741/2 GT was showing its age. Warmups are not something we do if there is no snow yet, because the owner's manual intructs the driver to begin moving immediately at 1500 rpm and to return the choke home as soon as backfiring is no longer imminent. It was not late at all, just into the third week of September, and the GT had sat at the home of friends while we went to the F1 races with them in their sedan. But now it was time to sew our shadows back on and to go home and sleep so that we could get up and go to work to get paychecks to buy more MG parts. And the GT started with difficulty, as defined by not on the first three revolutions. Even with the choke full out, starting probably took twenty revolutions. This made us think it was time to check the choke adjustment, just to be certain that when the choke handle was pulled all the way out, the choke linkage was fully rotated. (We did not neglect that we had fitted HS4 carburetters in place of the HIF4 that should have been on the car. It was just that the HIF4 pair was in need of a rebuild, and we had a set of HS4 carburetters ready to go for another car. We did not really work on the linkage, which is a little different, enough to guarantee easy starting.) We discussed the problem, and decided that it was just the time of the year, and we had hit the magic temperature at which proper adjustment of everything became a little more important. But, we assured each other, the GT would run fine just as soon as it got warm.

By the time we had made the few miles to the tollway, the temperature had almost reached normal. But the car continued to balk and miss, and we had only a few hundred yards of 'all four firing' to enter traffic from the acceleration lane. Then the miss started again, and continued. We were concerned that the GT would lose enough power to make an emergency stop necessary, and we did not like the idea at all. Then we had full power for a while, and every thing looked a lot better. The GT was just taking its time warming up. This wishful thinking continued until the misfire began again, and we wondered how long we could continue. Stopping on a toll way is not a good idea unless there are very serious mechanical problems, and a steady miss that would still let us move at the speed limit was not one of them. It is just that we missed being in the fast lane, and were very worried that we would end up on the shoulder of the tollway trying the 'AAA' speed-dial button on our telephone for the very first time. And we were tired and wanted to be home.

Finally, we made it to the exit that would take us home on a series of secondary and suburban streets. Since we needed to stop for groceries, we took the opportunity to check the 'it is just a loose wire' scenario. We shined the little Maglite over the right side of the engine, and noticed a distorted reflection from the distributor cap. The various lines and indentations we expected to see were bright and twisted in places. It took us a few seconds to realize that the strange reflections were from liquid on the distributor cap. The puzzle resolved when we noticed the hanging drops from the heater valve above the distributor cap. Closing the valve with the control inside the passenger compartment caused the dripping to stop. We made it home, changed the valve, dried out the distributor cap with WD-40 and air, and continue to drive happily, and we hope, ever after.

In retrospect, every thing is simple to recount. The weather had gotten colder, and we had turned on the heater valve with the control to the left of the steering column. The heater valve leaked when it was opened, and the coolant dropped from the valve down to the distributor cap, where it leaked into the cap. The water in the coolant caused arcing inside the distributor cap. In fact, even after the engine became warm, water condensed inside the top of the distributor cap, resulting in the spark going to more than one of the plugs. This communization of distributor action (the opposite of what a distributor is supposed to do) resulted in very long warm-ups.

The comforting thought is that if the problem had not showed up as a slight leak in the fall, the valve may have failed with a much larger leak in the summer, perhaps resulting in a roadside emergency. The lesson here is that many of the parts on twenty- or thirty-year old MGs are twenty or thirty years old. Buy new ones, and be prepared to change them before they fail.

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