A Tale of Two Projects

This past weekend I spent time digging a giant hole in my front yard looking for a water main break. Fortunately I found the problem on my first hole as there were two likely places the leak could have been. Once I found the problem but before fixing it, my son decided he would try and resolve a problem with his car. In the process he learned that you never start another project until one is complete. As the water was off in the house, he couldn't wash his hands after working on the car until the first problem was completely solved. He also managed to break both his car and my other son's car in the process and so at the end of the afternoon, we went from having one project to three.

My son's problem was actually fairly simple. In the process of replacing the cylinder head on his 1996 Jeep Cherokee, we broke one of the temperature sensors that screws into the the engine. My son wanted to replace it with a new one and so he went to the auto part store. He immediately broke that sensor in the process of trying to put it in. Naturally that was the only one the store had. Fortunately he was able to bring it back, get his money back, find another sensor at a different auto parts store, and break the new sensor. Another trip to the second auto part store and he got another one. Yes, the temperature sensor is incredibly brittle and breaks easily. One would think they would make them a bit more resilient.

The 1996 Jeep Cherokee actually has two engine temperature sensors and the one my son kept breaking is the one that sends information to the temperature gauge on the dashboard. Unfortunately the new one told my son that his engine was overheating and so my son couldn't go out with friends that evening. He was pretty bummed. When we popped the hood and checked the engine, it didn't seem any hotter than normal and didn't have the usual signs of the radiator boiling over. So we needed to determine if the engine was really overheating or if the temperature gauge was bad.

I'm a firm believer in the saying that "A man with one watch knows what time it is, a man with two isn't quite sure." In 1997, the engineers at Jeep decided the second temperature sensor in the Jeep Cherokee was superfluous and removed it. Fortunately for us, our job was to tap into the second sensor on my son's Cherokee and see if it was giving the same high-temperature results. All we needed to do was to tap into the car's OBD-II computer. Fortunately my son has a code reader that is a little more sophisticated than mine and it reads various parameters that include the engine temperature. The only catch is that the car has to throw a check-engine code first. My son tried unplugging various sensors only to have the engine keep running without any problems. He even tried unplugging one of the spark plugs with no luck. Finally he pulled the plug on one of the fuel injectors and the car threw a code immediately. He checked the code and the engine parameters and discovered that the engine was in its optimal operating temperature. That means the gauge sensor was wrong and his car really wasn't overheating. We now know why the engineers at Jeep took out the separate gauge sensor and just use one now.

The weekend is over and the hole in my front yard is now filled in. My son's Jeeps is running fine and the erroneous temperature gauge seems to be fixing itself. My son has also fixed the problem that arose on my other son's car. It took a couple of days, but things seem to be back to normal. At least until the next weekend.