Q. I had a set of four tires put on my wife’s 1998 Honda Accord about 17 months ago. They have been driven about 10,000 miles since installation. For a while now she has had a slow leak that requires re-inflating to normal pressure. We need to do this about once a month. I suspected a leak around the bead rather than a nail. I took the car back to the tire dealer where I had bought the tires. When they advised me the car was ready, they presented me with a bill for $50 to buff the wheels. I did not get to see the wheels before or after this was done, so cannot comment on the work. Is this a necessary procedure to ensure adequate sealing? Is it a common and necessary practice? Or is it just a way to get more money from the customer?

A. Some alloy wheels will develop corrosion on the contact area where the tire bead seals against the wheel. This corrosion will cause a very slow leak. To properly repair the leak the tire needs to be removed and the wheel cleaned and polished. At the same time when the tire is installed most tire stores will use a bead sealer. The sealer helps prevent corrosion and seals any minor irregularities in the wheel.

Need second opinion

Q. Since buying my Mazda Protégé 5 used three years ago, I have done an astounding number of repairs. However, the past year has been the most heart- and bank-breaking. The check engine light goes on, I bring it to the garage, work is done, light is off, I drive away and a few thousand miles later the light is back on. In the past 12 months, I have replaced the battery, a cracked brake caliper, five head/fog lamps, the windshield, front shocks, the front exhaust pipe, the rear sway bar, an inlet snorkel, and two sets of spark plugs, ignition coils, two ERG valves and a catalytic converter. Despite all this work, the check engine light is still on and I’m told I may need many more repairs. What should I do? Should I put the parts in and sell the car privately or to a dealer? Should I try to sell the car as is? Should I fix it and hope that my repairs are over?

A. Certainly you have had your share of problems with this car. At this point I would get a second opinion of the overall condition of the car. Only then can you make a logical decision of what is wrong with your car and what needs to be done to repair it.

A fast idle

Q. I have a 1994 Oldsmobile Cutlass that has all of its regular maintenance. Lately when I start driving the car it idles so fast that it can reach almost 30 miles per hour without stepping on the gas. It can take 10 to 15 minutes before the car returns to normal. What can you suggest?

A. The high idle speed could be caused by any number of items. The first place to look is for a vacuum leak. If the engine has developed a vacuum leak the computer will try to increase the idle speed to compensate. The other items to look at are the throttle position sensor and the idle air control motor.

Speedometer problem

Q. I need some advice; I have a 1998 Volvo S70 with about 135,000 miles. The problem is the speedometer recently started to work intermittently. It also doesn’t seem accurate all the time. Is there a simple fix, or is it something that needs to go to the dealer?

A. The fix may be simple but finding the problem could be difficult. Like most of today’s cars you can test the system and look for computer trouble codes. Once you find the code it will help determine what the problem is. Possible problems are a faulty antilock brake module, damaged wiring or a possible faulty speed sensor.

John Paul is the AAA Car Doctor{+S}{+M}. He has over 30 years of experience in the automobile industry and is an ASE-Certified Master Technician. He will answer car repair and maintenance questions of general interest from projoCars readers every Saturday.

Write to Car Doctor, Features Department, The Providence Journal, 75 Fountain St., Providence, RI 02902. Or you may send an e-mail to projocars@projo.com. Be sure to put “Car Doctor” in the message field. Answers of general interest will appear in a future projoCars section.