O2 Sensor on Toyota Corolla, Overheating Ford Explorer, Effects of Fuel Cell Water Vapor, Urban Legend Debunked, Metric vs. SAE Tools: Mike Allen's Weekly Online Auto Clinic

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Q: Where are the oxygens sensor(s) located on a 1999 Toyota Corolla?

A: In the exhaust system, before and after the catalytic converter.

Q: We just recently purchased a 1996 Ford Explorer, and it has been overheating. When we bought it we added antifreeze because someone put in water instead. I put antifreeze in it this morning and drove it to work. The gauge that tells you if it is cool or hot went to hot but than went back down. I checked the levels when I got to work and they seemed to be ok. The radiator cap was cool, so what could it be?

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A: You probably need to bleed the air out of the system, which may involve opening one or more bleed screws while filling. The filler cap isn't necessarily the highest point in the system, and air can lurk.

Q: It seems to me there is a byproduct of fuel cells operation capable of producing vast environmental and safety effects that have not been addressed to my knowledge. So how about leading the way journalistically and reporting about the effect(s) of millions of vehicles spewing water vapor upon the worlds dirt, stone, asphalt and concrete roadways? How slick will the roads be? Will visibility be affected by fog, mist, or rain? Will the atmosphere cool or heat?

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I remember watching a petroleum refinery and an adjacent electric power generation complex, thirty years ago, spewing steam behind Long Beach, California, and producing local precipitation. What will be the effect of millions of fuel cells upon roadway safety and atmospheric heating and cooling?

A: Mile-for-mile, there's just as much water vapor, if not more, coming out of the exhaust pipes of conventional internal-combustion-engined cars and trucks as there might potentially come from fuel-cell vehicles.

Q: I remember an article in Popular Mechanics about 20 years ago when fuel flowed like water, that General Motors had mistakenly release in an Oldsmobile carburetor that run 80 miles on a gallon of gas. They bought the car back and nothing else was ever heard of it. Imagine what could be accomplished if they would make these things and give to the public at a nominal fee.

A: You remember an article that didn't appear in Popular Mechanics, then. It's an urban legend: no such car existed or exists. It's debunked in more detail on Snopes.com.

Q: My wife has a 2004 Ford Expedition. Are the bolt heads metric? I serviced military vehicles for 35 yrs and they had american sizes. To replace the brake pads on this vehicle do I need metric tools?

A: Welcome to last week. Pretty much the entire US automotive industry changed to metric over 20 years ago. For a while, there were some odd things like the Mustang that had a 302 engine with SAE-sized fasteners, mounted in a chassis with SAE fasteners, with a transmission with metric fasteners. As older components were redesigned, they were replaced by metric-sized parts. I think the only real inch-sized dimensions on new cars worldwide is the bead-seat diameter of the rim. So, you'll need metric sockets and wrenches. And probably even some Torx sockets for the brakes.

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