Dayton Daily News

Q:My Dodge Dakota is 5 years old and only has 42,000 miles on it. The truck has the original set of tires on it, and they appear to have adequate tread. Since the tire tread is good, should I consider replacing the tires because of their age? J.S., Egan , Mich.

A:Tires sure are much better than they used to be, but age does weaken them. In fact, there is a study under way in which eventually tire makers will likely place a recommended replacement date on tires.

Inspect the tires’ sidewalls and tread for signs of dry-rot, cuts, bulges, ply separations and any other damage such as a nail puncture. If you should find something stuck in the tread, do not remove it. Remove the damaged tire and install the spare. Take the damaged tire to a technician for examination and possible repair.

If you find a tire is suffering from dry-rot, bulges, ply separations, tread separations or has suffered any damage especially in the sidewalls, it’s a good idea to replace the tire. Any of these conditions can cause a tire to blow out.

Misguided air from air conditioner

Q:The air conditioner in my 2003 Oldsmobile Alero blows plenty of cold air, but it comes out of the defroster vents. The air no longer blows from the center dash vents or any other vent combinations on the control. What’s up? P.L., e-mail

A:This may be the result of a failed control on the dash, but before anyone tears into the dash, all electrical connections in the system should be inspected for proper security and corrosion. Sometimes just unplugging and then plugging a connection back together will cure a problem. A slight tug on a wire might return proper operation.

Also, all the vacuum lines should be checked for proper security, cracks and leaks. Sometimes a vacuum line is accidentally disconnected during other repairs or services. A cracked vacuum line should be replaced, however, if a line slipped off a fitting. Simply reconnecting it might return the system to normal operation.

Since the HVAC system in your vehicle has diagnostic capabilities, a check of computer diagnostic trouble codes may find a circuit or control that has a fault. If so, replacement of a control or repair of a circuit will fix the trouble.

Cruise control takes a break

Q:The cruise control in my 23-foot 1991 motor home with a Chevrolet 350 engine intermittently quits working. Twice I have replaced the servo, but this hasn’t cured the trouble. Do you think the controls on the steering column are at fault? D.W., e-mail

A:The trouble might be in the switch on the steering column. It’s also possible that the brake pedal switches have a fault or need adjustment. In addition to these possible causes, the linkage to the throttle might not be in proper adjustment.

It’s also possible a speed sensor has a fault. Testing should verify a failure. If it has a malfunction, replacement should be the cure.

If you have a factory repair manual, consider using the diagnostic flow chart to track down the fault. It will show you how to test sensors, adjust switches and suggest the proper tools to do the job.

Radiator service not related to failure

Q:The seatbelt and airbag lights have been blinking in my 1998 Toyota Corolla. This began right after a dealer technician flushed the radiator. The lights turn on when my wife slides the passenger seat forward.

The first time I took the car back to the dealer, it cost $1,200 to replace some linkage under the passenger seat. What else could be wrong? B.P., e-mail

A:You could tell your wife to leave the seat position alone, but you’d probably end up in big trouble. I hope I can help.

It’s doubtful that the radiator service had anything to do with the failure. Testing should determine which circuit has a fault. This could be due to a faulty electrical connection under the seat, or there may be a faulty sensor.

It’s also possible that a sensor or electrical connection at the front of the vehicle has a fault. If this is true, corrosion or a loose connection might be to blame. If so, all a technician might need to do is secure or thoroughly clean the connection.

Noise Results In Huge Repair Bills

Q:I’m a loyal Jeep owner who has owned Jeeps for many years. Presently I own a 1993 Jeep Cherokee with 192,000 miles and a 2000 Jeep Grand Cherokee with 77,000 miles. My 1993 has been a great vehicle. I’m unhappy with my 2000 Cherokee. Since owning the vehicle I have spent nearly $7,000 in repairs on power door locks and a driveline noise.

Dealer personnel have replaced the front and rear differentials, axles, drive shafts and more but the noise persists. This noise began at 61,000 miles and has persisted despite all of the repairs. Dealer personnel have told me that if I would have purchased a Kia repairs would have covered by the warranty. By the way the dealer sells Jeeps and Kias.

I want to remain a Jeep owner but I think that spending $7,000 on repairs that haven’t been effective in solving the trouble is a bit much. I’d like Chrysler to give me a break on the next Jeep I purchase. Can you help? C.J., West Chicago, IL.

A:Along with your 2-page letter you sent a thorough 14-page account of the service history of your Cherokee. Dealer personnel have replaced just about everything in the driveline except the perhaps the muffler bearings. Just kidding there aren’t any muffler bearings but if there were it appears a technician would have replaced them.

From the description of the noise more than likely a bearing isn’t fully seated or gears are not shimmed according to specifications. Something that has been replaced is not properly aligned. It also is possible that the noise is related to tire tread wear but I would hope an experienced technician would have ruled this out before tearing into the differentials, axles and other driveline components. You could continue to go to the dealer for further diagnosis or since you want to purchase another Jeep you could trade this vehicle and buy another.

I have forwarded your letter and service history to a Chrysler representative. Please let me know what happens.

Perceived Gain May Not Be Benefit

Q:I have a 2001 Ford Explorer SportTrac with 75,000 miles. I’m going to give it a tune-up. I know that platinum spark plugs are better than copper. I’m also aware that there are spark plugs with two and four prongs on the end but these cost more than spark plugs with one prong.

Do the spark plugs with multiple prongs last longer than spark plugs with one prong? Do they give more power? V.S., San Juan Capistrano, Calif.

A:Spark plugs with multiple electrodes allegedly provide a better spark to ignite the fuel mixture in the combustion chamber. They also cost more than factory original spark plugs and may not last any longer than conventional style spark plugs.

You might see an improvement in power but since the spark plugs in your vehicle have undergone 75,000 miles of wear no matter which spark plug you decide to install you likely will feel an improvement in performance so it will be difficult to judge the difference unless you compare performance under laboratory conditions while testing different spark plugs that are brand new.

Consider installing factory original equipment spark plugs to see how the engine performs. If you are not satisfied install a set of multiple electrode spark plugs and you may perceive that they perform a little better than factory original equipment plugs but maybe not.

Controversy Over Tire Inflation

Q:In a recent column you advised a reader to fill the tires according to the maximum inflation pressure on the sidewall of the tire. This could be dangerous. The tires should be inflated according to sticker commonly found on the driver’s door. Under and overinflation can affect the handling of the car and tire wear.

Can you comment? L.S., La Crescent, Minn.

A:In the column you mention I stated that the tires can be inflated a few pounds under the maximum inflation pressure. Over the many years I have been in this business I have found and many of my colleagues have discovered that the inflation pressure listed on the driver’s door placard or in the glove compartment is not the best inflation pressure for the tire, the load in the vehicle or handling.

I can tell you from my own experience that slightly raising the pressure under the maximum tire inflation depending upon vehicle load saves gas and increases tire life to the point where I have driven 80,000 miles without the need for new tires and handling is not compromised. Also, properly inflated tires are more puncture resistant. I do have to stress that I am meticulous about checking tire inflation and check them often for under or overinflation wear and unusual conditions such as ply separations, bulges, sidewall damage, alignment problems and out of balance wear.

Study after study has found that tire underinflation is a very common problem. If you were to randomly check the cold tire inflation of vehicles in a parking lot that have been parked for about eight hours you would likely find most of the tires are underinflated compared to the inflation pressures listed on the door placard. Years ago I was involved in a study and 70 percent of the vehicles checked had tires that were underinflated. There are many reasons for this.

Inflation pressure is not checked often enough. Service personnel at many repair shops don’t check the inflation pressure when a car is in for service. Also, when the inflation pressure is checked the tires are warm so the pressure might be within a pound or two of the pressure suggested by the carmaker but in actuality underinflated.

In addition to all of this the common inflation pressure gauge is not accurate to the pound. An inexpensive gauge might be plus or minus three pounds or more inaccurate. If you inflate a tire with a cheap gauge and the tire isn’t cold the pressure could be underinflated by perhaps six pounds. This is significant. This could cause premature tire wear, reduced fuel economy, affect vehicle handling and a tire is more prone to a puncture.

Cooling System Fan Takes A Break

Q:The cooling system fan in my 1994 Oldsmobile Ciera with a 3.1 liter engine doesn’t turn on. I’ve checked the relay and grounds. They are fine. I checked the fuses to find that they are ok. I applied 12 volts to the fan motor and it turns on.

What could be wrong? D.C., e-mail

A:The computer might have a fault. A temperature sensor may have failed. A low coolant level condition in the cooling system might be at fault. Perhaps the coolant is dirty and foul and needs to be flushed. Perhaps there is a poor connection in the circuit. If you have a factory service manual or subscribe to a repair manual internet service such as ALLDATA or Mitchell you should be able to trace the circuits and eventually find the cause of this condition.

In the meantime consider flipping on the air conditioner as this might turn on the cooling fan so you don’t overheat the engine. If it does overheat it could suffer severe damage and you might have to kiss it goodbye.

Squeaky Engine Spells Big Trouble

Q:There is a squeaking noise coming from the engine of my 2000 Ford Explorer. It sounds like a worn drive belt. It is not the drive belt because a technician removed it and the noise did not go away. The technician thinks the sound is coming from inside the engine. To me it sounds as though it is an external noise and not within the engine. Do you have any suggestions? C.P., e-mail

A:A squeak inside the engine usually is associated with poor lubrication. As a result, the engine usually destroys itself within a matter of minutes. When bearings within the engine are not properly lubricated friction causes heat and with each turn of the crankshaft the bearings wear and rub against the crankshaft. During this process they can squeak. Usually as this happens the engine begins to make loud knocking sounds as the clearance between the crankshaft and bearing widens.

Since your engine doesn’t seem to be knocking the squeak sound is likely not from inside the engine. If the technician insists that there is a problem within the engine, and wants to disassemble it, tow the vehicle to an experienced technician at another repair shop for a second.