Ask the Car Doc: Why is my brake warning light always on?

Q. I have an old and generally trustworthy 1998 Chevy S-10, and when I’m driving it the engine starts to idle very fast. This will happen until I take my foot off the gas. Once I do this, the idle will start to calm down. Could you tell me what you think the problem is?

A. There a several items that could cause this symptom. It could be as simple as a vacuum leak or a faulty oxygen sensor. At this point, I would want to check the engine with a “smoke’’ machine to look for vacuum leaks and a scan tool to check for sensor data.


Q. I have a 2002 Honda Accord, and the brake warning light remains on all the time. I have checked the bulbs, and the brakes stop fine, so what could the problem be?

A. The brake warning light will illuminate for a couple of reasons: if the parking brake is on, or the parking brake switch is faulty. The light will also come on if there is a leak in the brake hydraulic system, or if the brake fluid level is low.

Q. I was at the dealership and the service advisor tried to sell me an oil additive with my 30,000 mile service. He said if they put a can in the car with the oil change I would get better gas mileage and it would be turning the oil into a super-synthetic oil. I have been told that this is not true. I asked around and people are telling me this stuff is modern day snake oil. How are the dealers able to sell this stuff? Won’t it void my warranty? The service writer told me it would not, but I’m skeptical. By the way where did the term “snake oil’’ come from?

A. There is no additive that can turn conventional oil into synthetic oil. Most vehicle manufacturers don’t recommend adding any additional products during routine servicing. Some dealers will recommend certain products, but in reality it is more about profit than mechanical longevity. Regarding the term “snake oil,’’ the term became a generic name for many compounds marketed as miraculous remedies. One of my favorites was a product sold in the 1950’s called HADACOL. This product contained among other things; honey, vitamin B12 and a fair amount of alcohol. This product claimed to cure everything from arthritis to baldness, but most likely just got customers drunk. Follow the manufacturer’s maintenance schedule, and keep the additives to a minimum.


Q. I have a 1999 Buick Century with a 3.1 V6 engine. Whenever I let the gas tank get down to a quarter of a tank or less, the “service engine soon’’ light comes on. I have the check engine light shut off and when the tank get low the light comes back on, why does this happen?

A. The first place to start is to check the car for computer fault codes. Once the technician has the fault code, they should be able to properly diagnose and repair the problem. You will most likely find a problem with the evaporative emissions system.

Q. I like the idea of not buying gasoline, does hydrogen really have promise as an alternative fuel and how long will I have to wait for it? How about natural gas cars?

A. Hydrogen powered cars have a bit of the “chicken or egg’’ problem. Vehicle manufactures are a bit hesitant to mass produce hydrogen vehicles without a refueling infrastructure in place. Hydrogen manufacturers don’t want to build infrastructure without customers to buy the fuel. I have driven hydrogen cars and they seemed at least as good as their gasoline counter parts. For 15 years I have been hearing that hydrogen cars are ten years away, I’m still waiting. I believe in the near term hydrogen cars will have fleet applications only. I have driven a CNG Honda Civic and found a little of the same problem with the refueling infrastructure. The CNG Civic was a pretty good car to drive but refueling needed to be planned out. There are only two CNG filling stations within my 100 mile round trip daily commute.


Q. I would like your input about a problem involving my 2012 Nissan Murano. About two weeks ago, after getting a car wash, I noticed spot on the upper driver door just below the window. So when I went to the dealer a few days later for an oil change, I asked about the spot, they had their body shop look at it. After some effort was made to remove what they believe was tree sap the paint was badly damaged. I was then told that the top half of the door would have to be repainted to the tune of $300. But I am having a hard time understanding how I didn’t notice anything and how a speck of sap could have damaged the paint on my almost brand new car? I am disappointed in the situation and suspect about the quality of the paint. Any thoughts?

A. Tree sap, acid rain and any number of environmental airborne contaminants can very quickly etch and damage paint. I believe this is due to the more environmentally friendly paint used today. In years back, the paint was more robust but polluted both the air and water and wasn’t particularly healthy for the person painting cars. Today the paint is much safer, but just doesn’t seem as tough as the older products.

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