Auto Doctor: Old car's fuel economy issues can be diagnosed

A customer fills up at a gas pump

A customer fills up at a gas pump in Montpelier, Vt. (Sept. 27, 2013) (Credit: AP)

Dear Doctor: I've had an ongoing noise issue in the dashboard of my 2007 Pontiac Torrent behind the speedometer. When accelerating it sounds like water shooting through a hoola-hoop. I also had a fault code stating "a/c off, engine hot." I took it in for service where they replaced the thermostat and head gasket; this fixed the fault code, but I still hear that same sound. Is the gasket bad again, or are the heads warped? -- CB

Dear CB: The first step is to check fault codes. If there are no fault codes, then the technician will need to check for hydrocarbons in the cooling system. If hydrocarbons are in the cooling system, then this means exhaust gases are also in the cooling system, indicating a possible faulty head or head gasket. Also, check the a/c system charge and a/c high and low sensor value, as well as the coolant temperature value.

Dear Doctor: I have a 1990 Mercury Grand Marquis that's getting very poor gas mileage. The car was my dad's and when he first got the vehicle it got much better mileage. I would be safe in saying it is less than 10 mpg. The car seems to run fine and no "check engine" or any other indicator is showing on the panel. Is there anything I can replace or check to improve gas mileage? -- Larry

Dear Larry: The first step is to check the actual fuel mileage. This is done by filling the gas tank, setting the trip odometer on zero, driving the car 150 miles and filling the tank at the same gas pump and check how many gallons used for the mileage driven. Your Mercury is an older model vehicle with limited computer ability. It does not have capability to record lazy oxygen sensors and emission capabilities. You can have the technician remove the spark plugs and check their color. A basic engine performance test is also a good idea to make sure ignition timing is correct and engine thermostat is functioning.

Dear Doctor: I have a 2012 Nissan Frontier pickup truck. I have been told to change the brake fluid every 15,000 miles. I'm hoping you can provide me with some solid reasoning. Is it needed due to poor composition in the makeup of the fluid, cheap brake piping from the master cylinder to the brake pistons whereby the tubing rusts out and brake failure occurs, money making scheme, what? -- Brian

Dear Brian: Brake fluid attracts moisture and moisture causes corrosion and this leads to multiple brake problems, including sticking caliper pistons and also caliper seal leakage, as well as internal ABS problems. Changing the brake fluid is always a good thing and can help prevent corrosion problems. I would follow the manufacturer's recommendations, not dealer recommendations. The use of a simple food baste to suck the brake fluid out of the master cylinder on an annual basis is a big money saver and a good maintenance service.

Dear Doctor: I own a 2000 Cadillac Sedan DeVille with 81,500 miles. Lately, the "check engine" light has come on and stays on. In addition, the gasoline gauge does not properly reflect the amount of fuel in the tank. We have always serviced the car properly using the local Cadillac agency. Recently, the service rep has made all kinds of expensive repair suggestions. What causes the service engine to come on? -- J.P.

Dear J.P.: The "check engine" light will come on when the computer gets, or tries to send, a command that is out of its value zone. The next step is a simple connection under the dash to the ALDL connector, which is located in 90 percent of the vehicles, on the left underside of the dash. You need to have someone scan the computer to see what the fault code is and what system is affected. A "check engine" is a sign of something wrong; a "check engine" light that flashes is something that needs immediate attention.

Dear Doctor: I recently took a test-drive in the 2014 Subaru Forester. What is your opinion of this vehicle? I spoke to three mechanics who advised me that after 80,000 miles these cars develop mechanical issues (leaks). -- Norman

Dear Norman: I drove the 2014 Forester for a week. This is not the Subaru of years gone by. It's a great all-wheel-drive SUV crossover. You are not going to tow a boat or racecar with the Forester, however it will meet all the needs of a family requiring a multi-purpose vehicle. As far as quality fit and finish, Subaru has done a great job on this car. -- Junior Damato, Motor Matters

Junior Damato is an ASE-certified Master Technician. Email questions to info@motormatters.biz. Mail questions to: Motor Matters, PO Box 3305, Wilmington, DE 19804

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