Motoring Q&A: Use a 'fix-a-flat' product if necessary, but follow up with tire repair

Star Tribune (Minneapolis)July 18, 2014 

QUESTION: Last week I had a flat tire on my 2013 Buick Encore with only 4,500 miles on it. I got out my can of tire inflator and when I read the directions it said it could not be used on tires with pressure sensors in them. Is it because it would ruin the transmitter or because the sealant could not get into the tire? Could you use it in a real emergency? When I took the car to the dealer after putting on the spare, they said it was repairable and did so. I was told I was lucky because on all-wheel-drive vehicles you have to change all of the tires at the same time. I have never heard of this before - can you explain?

ANSWER: The primary ingredients in most emergency tire inflator "fix-a-flat" aerosol products are a liquefied propellant like non-flammable HFC-134a - the refrigerant used in air conditioning systems - and a latex polymer to seal the inside of the tire.

Some earlier products utilized flammable propellants, which created a danger for the service personnel repairing the tires.

The reason these products are not recommended for use in tires fitted with tire pressure sensors (TPS) is that the latex sealer may coat and interfere with the signal transmitted from the TPS, although this potential issue is still being hotly debated. What is absolutely true is that the latex sealer will have to be thoroughly cleaned from the inside of the tire, wheel and TPS. In addition, there is a potential issue with corrosion and delamination of chrome from the inside surfaces of a chrome alloy wheel.

Regardless, it is important to remember that these products are, at best, a very short-term, temporary "fix." The tire must be cleaned and repaired - if possible - at soon as possible.

Should you use an aerosol tire inflator in an emergency such as being stopped in a dangerous scenario or situation where taking the time to mount the spare tire would add to the risk? I would. If the fix-a-flat product will inflate and maintain enough tire pressure to allow me to drive to a safe location, I would certainly use it.

But I'd make absolutely sure to tell the service agency that you used a tire inflator and have the tire repaired or replaced as soon as possible.

The reason for suggesting that all four tires must be replaced at the same time is because four-wheel or all-wheel-drive vehicles must have all four tires with the same rolling circumference or potential damage to the drivetrain can occur. As long as the single replacement tire is virtually the same rolling circumference as the other three tires, there is no problem.

Q: I have a '96 Chrysler Concorde with 94,000 miles. The needle on the gas gauge is not functioning right. At times it is normal, but at other times the warning light goes on and the needle fluctuates. Is this a big job to repair? I can keep track of the mileage with the odometer so I don't run out of gas.

A: The position of the needle on the gas gauge of your vehicle is controlled by the body control module (BCM). The BCM receives a signal from the variable resistor in the sending unit in the fuel tank, compares this with the fuel tank ground and moves the needle to the correct position on the gauge.

The intermittent issue with your gauge may well be the variable resistor/sending unit in the fuel tank, which is a significant repair, or maybe just a poor ground for the variable resistor which is located in the left kick panel. With the age of the vehicle, I'd first make sure this ground connection wasn't the problem.

Also, remember that the LED light in the gauge will also illuminate if engine temperatures reach the 240-260 degrees F range.

ABOUT THE WRITER

Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor and former race-car driver. Readers may write to him at: Star Tribune, 425 Portland Ave. S., Minneapolis, Minn., 55488 or via email at paulbrand@startribune.com. Please explain the problem in detail and include a daytime phone number. Because of the volume of mail, we cannot provide personal replies.

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