Dayton Daily News

Q: The overdrive light in my 1999 Nissan Frontier with a 4-cylinder engine stays on but the overdrive in the transmission is engaged. I don’t mind driving the vehicle all the time when it is in overdrive but I fear this is harming the vehicle. Is this something I should be concerned about? What would cause the light to constantly be on? W.S., West Chester , Ohio

A:Operating overdrive full-time is not harmful to the vehicle. The transmission is designed to engage overdrive when cruising. However, if you drive with heavy loads such as pulling a trailer or driving on steep grades, the overdrive feature should be turned off. This is to prevent the transmission from overheating and provide engine braking when driving in hilly terrain. Since you can’t disengage the feature by tapping the button, avoid these conditions.

The trouble might be the result of a sticky valve inside the transmission. A transmission flush might cure the trouble. It’s also possible there is a faulty connection in the circuit that controls the overdrive function. Testing by a certified technician should be able to determine the cause and suggest a lasting cure.

Project truck needs new throttle linkage

Q:I have a 1964 Chevrolet C-10 pickup truck that I purchased in 1979. I’ve been restoring the vehicle since 1989 and drive it very little. I took the 6-cylinder engine out and replaced it with a 283 c.i.d. V-8. I used the throttle linkage from the 6-cylinder engine on the V-8. Now I have discovered that the carburetor does not fully open.

Since I don’t use the truck much should I add a fuel stabilizer to the gas tank? Do you think I should replace the throttle linkage? Also, if the carburetor floods will this ruin the spark plugs? P.C., Norfolk , Va.

A: In your letter you stated that the truck was recently painted, carburetor repaired and more. You have done a lot of work on this project vehicle.

For proper throttle operation the throttle linkage should be replaced with linkage meant for a V-8 engine. You might find it on the Internet.

As for using fuel stabilizer this also might be a good idea. Make sure to follow the directions on the container of the product you decide to use.

As for the spark plugs, they will foul if the carburetor floods the engine. If this occurs replace the spark plugs. Also, if the flooding condition was severe gasoline likely contaminated the engine oil. If this has happened you might detect a gasoline odor in the oil. An oil and filter change will help prevent damage to engine bearings of your recently installed V-8.

Brake line needs replacement

Q: I have a 1993 Mercury Grand Marquis that was involved in a frontal collision. The steel brake line to the brake master cylinder has a slit or hole in it. When the brakes are applied, I can see a fine mist spray from the brake line. I need to replace or repair it. I called a few auto parts stores to learn that the line is no longer available. Is it possible to brace it to repair it? What should I do? F.V., Garden Grove , Calif.

A: The line should be replaced. An auto parts store counter person should be able to help you choose a proper generic replacement.

The steel line should be replaced from the master cylinder to the first union, joint or valve. To do this, you will need to remove the punctured line and measure it so that you can purchase a replacement of the proper length. You will need to bend the new line with a special bending tool so that it won’t kink or break. A parts person can set you up with the proper tools and fittings to perform the work.

Once the new line is in place, bleed the air from the brake system using factory- recommended procedures outlined in a repair manual, and use the factory recommended brake fluid.

Carburetor leak fouls engine oil

Q: Up until two months ago, my 1984 Honda Accord with 196,000 miles has been running great. My wife complained that she smelled gasoline, so I replaced the fuel filters. This didn’t cure the trouble, and I discovered that the gasoline was in the engine block. As a result, I replaced the fuel pump and changed the oil. After this I was able to start the engine and run it. I changed the oil again, but fuel continued to enter the block. I returned the new fuel pump to the store and reinstalled the old pump. Do you think this problem is caused by a faulty fuel pump? R., e-mail

A: It’s possible, but unlikely as installation of a new fuel pump did not cure the trouble.

More than likely, the trouble is caused by a faulty carburetor. The carburetor may be leaking fuel from the fuel bowl into the engine block. A visual inspection of the throat of the carburetor may find fuel dripping into the engine. If so, an overhaul of the carburetor or installation of a remanufactured carburetor should cure the problem.

Examine the carburetor immediately after turning off the engine. The fuel pressure will cause a faulty carburetor to leak.

Until this trouble is solved, do not drive the vehicle. From what you describe, gasoline is contaminating the engine oil. This will impair the ability of the oil to lubricate bearings and moving parts within the engine. This could result in severe damage that could ruin the engine.

Once the condition is repaired, change the oil and filter immediately after the repair and two more times within 1,000 miles of the repair. This will remove any residual gasoline in the oil and inside the engine block.

Slick fix for power windows

Q: The power windows in my four-door 1992 Chevrolet Blazer only run part-way down and then quit. If I let them sit for about five minutes, when I move the switch to lower them, they will move a little more.

I replaced the circuit breaker for the system, but the windows continue to quit part-way up or down. I suspect the motors have failed, but it’s hard for me to believe that all four window motors failed at the same time. Is there another circuit breaker in the system that I have missed? G.L., Joliet , Ill.

A: The system in your vehicle is fairly straightforward. There is one 30-amp circuit breaker providing electrical power, the driver’s door control, switches for the windows in the other three doors, a motor in each door and wiring connecting everything together to power from the breaker and a ground connection in the left side of the dash.

It’s not likely that all four window motors failed at the same time. Consider applying a liberal amount of automotive silicone spray lubricant to the window channels that guide each door glass. You might need to purchase a couple of cans of lubricant to do a proper job. Lower a window at a time. As the glass lowers, apply the spray lubricant to the channels at the front and rear edge of the glass. The lube job may return normal operation.

Also, make sure that the ground connection in the left side of the dash is free of corrosion and secure. Check all the connections at the switches, too. Fix if needed.

If these attempts don’t cure the trouble, it’s possible each motor has weakened as a result of time and mileage. If so, replace the motors.

Minor collision causes total failure

Q: Recently my husband was driving our 2006 Kia Spectra at about 7 mph when he rear-ended another car. There was no apparent damage to either car. Unfortunately since the collision, our car won’t start. We are told that there isn’t a fuel cut-off switch or anything such as this that would impair the car. Have you ever heard of anything such as this? M.N., e-mail

A: Vehicles are complex pieces of machinery. Also, quarters are cramped, so there isn’t a lot of space for the electronics and drivetrain. As a result, even a low-speed collision reverberates through the entire car with a jolt. This can jar a connection loose.

Maybe the battery jumped a bit. In doing so, it’s possible the positive cable hit sheet metal and caused a momentary short circuit. If so, it’s possible a circuit breaker opened or perhaps a sudden change in polarity caused the engine control module to fail.

Once a technician probes for the trouble, it shouldn’t be too long before the cause of this condition is found. A lasting cure should follow.

Misdiagnosis A Possibility

Q: My girl friend owns a 2000 Chevrolet 4X4 Silverado pickup truck. She hears a hum sound that seems to come from the rear of the truck when slowing from 50 mph. The tires have been rotated and balanced. There aren’t any loose shields on the exhaust. The spare tire is tight and all the driveline u-joints appear fine. Dealer personnel tell her that the source of the noise is a worn u-joint.

I did some research at the library and found some information that the noise might be caused by the transmission. However, dealer personnel tell her the transmission is fine.

Currently I’m 3,000 miles away and can’t help my girl friend. Do you have any suggestions? R.L., Elizabeth City, N.C.

A: Dealer personnel have the latest technical information, tools and expertise to diagnose just about every problem that can occur. If a technician has a problem that he is having difficulty in pinpointing he can tap the vast information and technology that General Motors provides to dealerships. Much of this information is private and only accessible to their dealer body. If a technician has determined that the noise is caused by a failing universal joint in the drive shaft it is more than likely the cause of the humming sound. Replacement is the cure.

It is however possible that the trouble has been misdiagnosed. Your girl friend might consider taking the truck to another repair shop where a technician might consider that the sound is caused by wear patterns in the tires. If so replacing the tires might end the concern.

It’s also possible the cooling system fan or driveshaft has a fault. In addition to these suggestions perhaps the driveshaft slip joint needs lubrication or if it excessively worn, replacement.

Failed Oxygen Sensor Needs Replacement

Q:Recently the check engine light illuminated in my 2003 Chevrolet Venture with 48,000 miles. I took the vehicle to my dealer where I received a report that stated that it looks like the oxygen sensor is failing. Dealer personnel offered to replace the part for $196. When I asked if the replacement would cure the trouble I was told “maybe”. I thought that for $196 the cure would be guaranteed.

The fuel economy is as good as it has ever been, about 24 mpg. Also, there hasn’t been any change in performance. Can you provide any help? D.S., Suffolk, Va.

A:There are three levels of failure that turn on the check engine light. Depending upon the severity of the condition that caused the computer to turn on the light determines the level of failure. When the light illuminates a failure code is stored in the computer. A technician’s diagnostic tool reads the code. The code tells him or her which circuit or part has failed.

In your case the code was related to the oxygen sensor. The circuit might have a fault. The sensor may have failed or the heated portion of the sensor might have failed.

Testing the circuits might find a loose connection, corrosion or a fault in a plug such as a loose pin. Tests of the sensor may find that it does not respond quickly enough or the voltage it produces is out of factory specifications. With the information at hand a technician decides the best course of action. He can repair a circuit or replace the sensor if needed. Apparently in your van the best action is to replace the sensor.

There might be other problems. If there is a condition within the engine such as an internal coolant leak, dirty throttle body, aftermarket fuel additives, leaky fuel injectors, contaminated gasoline, poor gasoline formula, vacuum leaks or other conditions that are causing the oxygen sensor to run amuck installation of a new sensor may not cure the condition. Hopefully this isn’t the case and a new sensor will end your concerns. Having said all of this from what you describe a new sensor should do the trick.

Thanks for all of your great questions. Dr. Gizmo looks forward to more.

Phil Arendt is an automotive columnist, consultant and

ASE-certified master technician.

E-mail him on the Web at http://www.drgizmo.ws.