Q: I have a 2004 Toyota Avalon that recently appears to be leaking water from somewhere. The floorboard on the driver's side is soaked and I cannot tell where it is coming from. Any insight you can provide would greatly be appreciated.

C.S., Coral Springs, Fla.

A: Water leaks can be as elusive as mermaids. Leaks into the front passenger area are often due to a poor seal at the windshield, especially if it is a replacement windshield. Another likely source is a clogged drain for your sunroof. Sometimes leaks develop at body seams that are not adequately sealed following a collision repair. You are not likely to see evidence since the water often flows behind the kick panels. You may spend hours fishing for the flaws.

Q: I had the tires replaced on my 2011 Honda Civic recently. It's my first experience with a tire pressure monitoring system, so I wasn't surprised when I was charged $7 per tire for a rebuilding kit. I was surprised when I was told that two of the sensors were "frozen" on the wheel and broke when the technician removed them at a replacement cost of $60 per unit. They eventually dropped the price to $40 per unit. Is it normal for these units to freeze on the wheel, and can I do anything to prevent this in the future?

B.W., Downers Grove, Ill.

A: It is becoming standard practice to replace the seals and retaining nuts on tire TPMS sensors. It is cheap insurance against a potential future leak. Sensors also can become corroded to the point that they break during service. Corrosion usually happens when someone installs fancy aftermarket metal caps that develop a galvanic reaction, especially where salt is used to treat the roads. We like to replace the original metal valves and sensors with rubber ones that resemble the tried and true valves of the past. No fuss, no rust, no leaks.

Q: I have a 2014 Mazda3 with a 2.5-liter engine that calls for 4.8 quarts per change with the oil filter replacement. When I refill the engine with oil, it requires 5.2 quarts to get to the top of the dipstick. The dealer said it should only take 4.8. I am wondering if this is due to the fact that I drive it up on ramps, which tilts the engine to provide a more sufficient drain than the dealer's lift, which is flat. If so, I think I am getting a more sufficient oil change with the ramps.

T.R., Chalfont, Pa.

A: Your Mazda engine calls for 5 liters of motor oil. That works out to 5.3 quarts. You probably need only 5.2 quarts because not all of the oil will drain. Some sits in the cylinder heads and other sneaky places. Your dipstick provides a safe operating range so, with that in mind, we would simply pour in 5 quarts and stop worrying — ramps or no ramps.

Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber's work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest Send automotive questions along with name and town to motormouth.tribverizon.net.