Sparking Interest in Copper-Core Plugs
Question: What are the advantages or disadvantages of the copper spark plugs that are now on the market? I have an older car, and I was wondering if they would work as well as the ones specified in the owner’s manual.
--J.E.M. Answer: Copper-core spark plugs are designed to prevent “fouling” of the plug tip with carbon and other deposits, a condition that can lead to engine misfiring. In stop-and-go driving, the engine never runs fast enough for the spark plug to reach its optimum operating temperature. The plug only gets up to around 600 to 700 degrees, which isn’t hot enough to prevent carbon created by the combustion of gasoline from accumulating on its tip.
The problem facing engineers is to design a plug that will quickly get hot enough to keep the deposits from building up, but not get so hot in high-speed freeway driving that it causes the air-fuel mixture to ignite prematurely.
The copper-core plugs (the copper is encased in nickel alloy) have a slightly longer tip than conventional plugs (which are made entirely of nickel alloy). The copper plugs thus protrude deeper into the hottest part of the combustion chamber. Being longer, they have a larger surface area on which deposits can accumulate, helping prevent the carbon from becoming too thick in any one spot before a trip on the highway can burn it off. This also helps the plug get hot more quickly. And because copper is a better conductor of heat than nickel, the heat can be dissipated before the plugs get so hot that it causes preignition. If conventional nickel-alloy plugs were as long, they would not dissipate the heat quickly enough and would overheat.
Ordinarily, a high-speed trip makes the plug operate at its optimum range of between 750 and 1,500 degrees, burning off the carbon. The heat range varies with different types of cars, and an advantage of the copper plugs is that they operate over a wider heat range than the conventional variety.
The plugs usually cost about the same as the nickel-alloy type and are available in sizes to fit nearly all cars. Switching to copper-coated plugs in your car could help the engine run better.
Q: I have a 1983 Buick Regal. Every once in a while, the coolant temperature gauge goes all the way over past 260 degrees, and the engine isn’t even hot. It doesn’t creep up; it just suddenly goes over to the maximum reading. I’ve been to the dealer twice, and his mechanic can’t find anything wrong. What could cause it?
--J.O. A: The temperature gauge works off a sensor that screws into the side of the engine near the water pump. The sensor controls the flow of electrical current to the gauge, depending on the temperature of the coolant. If the sensor isn’t working, the gauge probably wouldn’t work at all, so the problem is most likely in the gauge itself.
The gauge works by creating a magnetic field with the current from the sensor, which causes the needle to move to the correct reading. If the gauge suddenly receives a sharp burst of current due to a short circuit, it could peg to the maximum temperature. Heat from the engine manifold could have burned the insulation off the wire that runs from the sensor to the gauge, causing it to short out occasionally. The only solution might be to find the cause of the short, or, if it’s inside the gauge, to replace the unit.
The gauge is more expensive and harder to replace than the sensor, so have the sensor checked--and perhaps even replaced--before you pay to have the gauge worked on.
Patrick Boyle cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.
