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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 12
by Bob Hagin
Q. I have a 1997 Dodge Ram pickup truck with the Cummins diesel engine. When I'm driving the truck and it is warmed up, the temperature gauge constantly fluctuates between 110 and 180 degrees. I've taken it back to the dealer who sold me the truck and there the mechanics make a joke out of it by telling me that some diesels do it while others don't. I have only put 3500 miles on this truck. I have been told that this engine has some kind of clutch system on the cooling fan.
A. You're a very patient person to put up with having a mechanic making a joke out of your concern for your very expensive purchase. Since you've already brought your problem to the service manager of the selling dealer and he can't or won't help you, go find another Dodge dealer who will. A diesel engine that is showing signs of temperature fluctuations and overheating may be getting ready for a major problem. Your truck is no doubt still under the Dodge warrenty so you can call in the factory field representative through any Dodge dealership. Dodge is making a big thing out of its reputation for building tough trucks and I don't think it would want to damage it through the neglect of a disinterested dealer. I've passed your letter on to a person I know at Dodge and perhaps she can help you. Let me know what happens.
Q. I have a 1994 Toyota Camry. Someone told me that I should avoid buying gasoline that has ethanol in it. I didn't know that there were differences in gasolines and I often chose the cheapest. This person told me that ethanol could be very hard on my car. Is this true? If it is, how do I know which gasoline has ethanol in it? Since he told me this, I've been buying the more expensive brands. Do I need to do this?
A. "Gasoline" is really a catch-all word for motor fuel that is a blend of several volatile petroleum distillates. The blend varies from area to area and is usually changed by the manufacturer as the weather changes. In cold climates, gasoline is blended to volatilize at a lower temperature so that your vehicle will start easier. In hot weather, the blend is compounded to volatilize at a higher temperature so that it won't turn into a vapor before it gets into your engine in which case it wouldn't run. This is referred to as vapor lock. Gasolines often contain additives that do different things (resist rust formation, clean fuel delivery parts internally, reduce pollution emissions, etc.) and ethanol is one of these. Ethanol is drinkable alcohol that's added to gasoline at no more than 10 percent by volume since higher ratios tend to affect drivability. When it was first put into gasoline in the '70s, it had a tendency to attack the rubber-like parts of the fuel systems of older vehicles. Modern cars like your Camry are designed with the use of ethanol-laced gasolines in mind but if you're worried about it, check your owner's manual under the section regarding recommended fuel types. Methanol (wood alcohol) is another story and Toyota and all the other auto makers suggest that you avoid gasolines that contain it.
Q. I have an '87 Olds Cutlass with a 5.0 liter V8. The car has 77,000 miles on it and has been well maintained. Lately it has developed a noticeable increase in spark knock when the engine is warm and after 10 minutes of driving. The timing checks out as well as a computer analysis. I've replaced the plugs, plug wires, oxygen sensor and have cleaned the carburetor. I've also tried different kinds of gasolines all to no avail.
A. If your exhaust gas recirculation (EGR) valve is inoperative, your engine will knock when it warms up. It's also possible that you've got a carbon build-up from short-trip mileage on an older car so you might try a chemical combustion chamber cleanup too.
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