Question: I own a Saab 900S. A few months ago, I made the mistake of using an abrasive sponge to clean the windshield, which resulted in a scratched area about four inches in diameter. Is there any way to rub or buff out these scratches?--M.M.
Answer: The short answer is that your mistake is probably going to cost you a new window, especially if the scratches are in a critical area that affects your view of the road. You can try to rub out the scratches, but chances are that you will not succeed.
The lesson here is that you should never use anything but a cloth or soft sponge to clean glass. If you have paint, tar or sap on a windshield, then it can be safely scraped off with a razor blade.
As for repairing your windshield, if the scratches are so deep that you can feel them with your fingernails, then the windshield is beyond repair. Even if you can smooth the scratches over, you will be left with a distortion in the glass that will be irksome, if not dangerous.
If the scratches are only superficial, then it may be possible to remove them. It's best left to a professional auto-glass shop, because glass work is a black art that few laymen ever master.
But if you are intent on trying something yourself, you should first smooth down the scratches with very, very fine wet and dry sandpaper, such as 600 grit or 800 grit. Then you would buff the area with a glass rouge, such as cerium oxide, which is usually sold only at glass-supply shops. Buff the area with a hard felt pad on a buffing wheel or electric drill.
You should expect to spend a lot of time and be fully prepared to fail.
Q: I have a 1983 Cutlass Ciera with a three-liter engine. When I first start the car in the morning, the engine runs really fast and it will not slow down. I have to use my brakes heavily when I back up. I also have to wait for the engine to slow down when I put it into drive. The Olds garage says this is normal. Is it?--R.A.
A: Unfortunately, it probably is "normal," but that doesn't make it any more acceptable. Although it may seem a reasonable expectation that a car should idle smoothly, you are probably going to have to get used to jarring starts.
The fast idle is a function of the choke mechanism on your carburetor. The function of the choke is to give the engine more gasoline when it is cold, partly by increasing the fuel in the the air/fuel mixture and partly by speeding up the idle.
Oldsmobile specifications call for your engine to be idling at about 1,800 revolutions per minute when it is cold, which is pretty fast. Many other cars have a cold-idle setting of no more than 1,200 rpms.
Q: I think I may have a helpful hint for the reader who recently wrote complaining of a rotten-egg odor in his car. My car had the same problem, and it was finally solved by replacing the battery.--T.M.
A: A leaky battery can apparently cause a sulfuric odor, which may travel from the engine into the passenger compartment. Such leaks are rare in new, sealed batteries, but a defective battery is a possibility. In many other cases, however, sulfur odors originate in the catalytic converter.