Q. I own a 2004 Jaguar 3.0L X-type AWD. Late this winter, the car developed a high-pitched, almost siren-type noise while traveling 25 to 30 miles per hour. The first couple of times it occurred, I thought it was a police car’s siren. I can’t find a location where it originates, as it seems to permeate the car. I thought it may be a vacuum hose of some sort but I didn’t find anything disconnected, nor did my local auto mechanic. With summer here and some upcoming vacation plans, I would like to get this fixed. Any idea where this annoying noise could be coming from?

A. There are at least two technical service bulletins (TSBs) that address a whining issue. The first has to do with a transmission shift cable allowing sound to resonate into the cabin (TSB number XT308-04). The second issue is with the driveshaft; some models have a driveshaft that produces an objectionable whining noise (TSB number XT100-09).

Q. I own a 2005 Toyota Camry and have its oil changed at the dealer. I’ve owned other Toyotas before and I’ve been happy with them. On a recent visit, however, it was suggested that the transmission fluid be changed—a $255 charge. We also have 50,000 miles on the car and the original tires show wear on the outside area. What would you recommend on these two subjects?

A. Tires are one of the most important safety items on any car. Tires that are worn affect how well the car will handle and stop. At five years old and with 50,000 miles, the tires are likely in need of replacement. Regarding the transmission fluid, Toyota doesn’t have a specific recommendation for transmission fluid service. In fact, Toyota issued a technical service bulletin that stated Toyota World Standard (WS) fluid doesn’t require any flushing or changing during the life of the vehicle.

Q. I have a 2008 Ford Escape Hybrid 4WD with 31,000 miles on it. A clunking sound has developed in the driveline (shaft) and occurs infrequently upon slowing to a stop. It feels like the driveshaft is being disengaged from the transmission. The Ford service technician drove the vehicle but the clunking noise didn’t occur. The service advisor says hybrids make unusual noises, but I don’t think this is considered a “normal” vehicle noise—nor one I can live with.

A. I have checked technical service bulletins and found mention of a sound shield, although in this case, it was to mask a high-pitched noise. It is true that hybrid vehicles tend to exhibit a little more noise than conventional internal combustion engines. I would continue to document the noise whenever possible should a problem develop outside of the warranty period.

Q. I have a 2003 Pontiac Montana with 94,500 miles on it.  Over the past year or so, I’ve noticed a gasoline smell coming through the vents while running the heater. It’s most noticeable when the vehicle is parked and running, or while it’s idling in traffic. It’s least noticeable while moving or running the heater on re-circulated cabin air. The van is also using more gasoline than usual. I’ve been to two GM dealerships that have been unable to identify or resolve the problem. One changed the cabin air filter; the other changed the fuel pressure regulator. Any thoughts on what could be causing this?

A. If you can smell gasoline, there is a problem—although not necessarily a gas leak. The best tool I’ve seen to find a fuel leak is an infrared gas analyzer. They are not used as often as they once were, but these gas analyzers are great for sniffing out a fuel leak. Keep in mind that it may be “raw” gas, or it could be fumes from the evaporative emissions system. A good technician may suggest the use of a smoke machine. By using this, in conjunction with a scan tool, the technician can operate the various solenoids and look for trails of smoke.

Q. When my 2003 Honda Accord is driven at or above 40 miles per hour and the brakes are applied, the front end begins to vibrate. At the dealership, they removed the front wheels and determined that the front rotors needed to be machined or perhaps replaced. Not only did they charge $54.50 for this “test,” they would charge $180 to machine the rotors. On a second call to the same dealer, I spoke to a different service manager who told me they could use a micrometer to test each rotor and clean the rear brakes for $39.99. Could the problem be different than the front rotors? Could you tell me if there are any technical service bulletins (TSBs) or any recalls on this model related to the vibration?

A. From your description, it sounds as though there is a brake problem. Although you can check the brake rotor with a micrometer, the best tool is a dial indicator, in my opinion. This tool mounts to the car and measures the run out of the rotor. Regarding the charges, you should expect to pay a labor charge when you have a vehicle inspected. The brake rotors on Honda vehicles need to be resurfaced with an “on-the-car” lathe. According to my guide, the labor to remove the calipers and resurface the rotors is about one hour per side. In this case, the prices look fair. I don’t know of any recalls regarding the brake system on your car, although there are several technical service bulletins. These TSBs address brake vibration, but they don’t provide any financial relief outside of the warranty period.

Q. I recently realized that my car’s gas cap is missing. As a result, the check engine light stays on. What risk does this pose to the vehicle? How swiftly should I move to resolve the matter?

A. All you need to do is replace the gas cap. It should be done as soon as possible to keep out water and contaminants. In addition, the gas cap is part of the emissions system—without the gas cap, you are allowing gas vapors to venture into the air. It’s important to note that once you replace the cap, the check engine light won’t go out immediately. It will shut off once the computer performs a series of checks—usually after driving 100 miles.