Ask the Auto Doctor: Transmission fluid needs to be changed
Q : My Toyota RAV4 has 100,000 miles. I followed the owner’s manual recommendation and never changed the transmission fluid. The fluid is now a grayish brown color. Mechanics have said if I change it now I may experience transmission problems. Should I change it due to coloration change? A : I would recommend changing the fluid. This is done on most Toyota vehicles with a simple drain plug in the transmission pan. When the plug is removed about 3.4 quarts will drain out. I suggest you continue to do a fluid drain once a month for the next three months. This will slowly change the fluid over time without any concern. Make sure you use only factory Toyota transmission fluid.
Q : My 1995 Mercury Grand Marquis has a whining sound from under the hood. The sound changes with engine speed. What’s causing the noise? A : Have a technician look at both the power steering pump and alternator and use a stethoscope to listen to belt-driven accessories.
Q : I make a regular trip that has always measured between 191 and 192 miles; however, in my 2008 Nissan Frontier that I bought used the trip measures 198 miles. Can odometers be calibrated on a used car purchase? A : Yes, the odometer can be re-calibrated. It is done electronically by reprogramming. Tire size also plays a part in calibration and correct speed and odometer readings. You can have the dealer check the vehicle.
Q : My 1996 Lincoln’s front air shock boots have deteriorated and leak. Can I replace these air shocks with conventional ones? If so, will there be any appreciable handling or steering difference? A : I see many vehicles with air suspension failures and I always suggest the conversion over to conventional coil spring assemblies. The vehicle will ride and handle better than the old air suspension.
Q : The doors began unlocking themselves on my 1997 Chevy Lumina after I had parked the car and locked them. Later, they began unlocking themselves while I was driving. Now, they lock and unlock while I’m driving. The dealer replaced the driver’s side door lock switch, but the problem still exists. What do I do? A : There is a trouble flow chart to test the system. The most common failure is the alarm module (body control module). A voltage test at the connections is also required. Have the technician check all the fuses, as well as the driver’s outside door handle.
Q : I own a 1995 Chevrolet Lumina 3.4-liter V-6 engine. When starting the cold engine it races to 3,000 rpm and then stalls out. When the engine is warm it idles fine. Can you Help? A :A technician will need to hook up a scan tool before starting a cold engine to monitor all sensor values. Next, he’ll start the engine and continue to monitor the scan tool and compare the actual readings to factory specs. Other areas to look at are small vacuum leaks. Dirty fuel injectors could also be playing a roll in this problem.
Q : I own a 1996 Pontiac Bonneville 3.8-liter V-6. The engine is hard to start and the idle also fluctuates, sometimes racing at high engine speeds. What should I look for? A : The hard starting can be low fuel pressure, dirty throttle body, coolant sensor out of range and a host of other problems, including a vacuum leak. With an unstable idle and a loss of vacuum to the power brake booster, the braking in your car will be reduced greatly. Due to safety concerns, I recommend you get the car to a qualified repair technician.