Q: I have a 2002 Lexus ES300 with 185,000 miles on it. Some time ago, the ABS and brake light came on simultaneously. I took it to the shop, which diagnosed a faulty ABS sensor. They said that I did not really need to replace it because it would cost close to the value of the car and that, even with a faulty ABS system, the normal braking would work fine and I'd just need to be more careful about braking in inclement conditions. I have not noticed any problems with braking. I don't really want such an expense for an old car. Should I be concerned?

A: The anti-lock braking system (ABS) provides significant safety, especially in slippery conditions. Under normal conditions, however, the ABS does not kick in. So your shop is correct, but keep their admonition in mind when you drive in bad weather. You also might want to consider getting a second opinion on the repair. Because the problem is intermittent, I suspect a bad sensor or electrical connector, and the fix might be less costly than you think.

Hard-earned know-how

Q: My older brother is very good with all mechanical things. When I ask him how he learned so much, he simply says, "poverty" with a chuckle. I wonder how you learned so much about cars. It amazes me how you know the answers to the strange questions. I have to ask my son or daughter-in-law how to reset the clock for daylight saving time.

A: Poverty is an inspirational teacher. I, too, lacked money, which forced me to maintain and repair my cars myself. I learned from many mentors and lots of factory training when I worked as a professional mechanic. To keep up to date, I still read trade publications (I used to be the editor of one) targeted to professional technicians. When I am stumped by a question, I turn to my cadre of techs and aftermarket suppliers for help. And, yes, I check the internet. Some of the information online is helpful, but there also is a lot of poor advice that we must take care not to follow.

Antifreeze chemistry

Q: How is it that pure antifreeze freezes at zero degrees F., and water freezes at 32 degrees F., yet when a 50/50 mixture of each, the mixture freezes around 36 degrees below zero. (All these figures are for sea level.)

A: Speaking of getting help with tough questions, I had to turn to the folks at Prestone to explain this one. The simplest way to think about it is that water and antifreeze (ethylene glycol) are both pure, but when they are mixed, they react with one another to form a new molecule that has a whole different set of properties and performance.

Prestone said that the cold freeze performance and hot boiling performance max out at a 70/30 mixture. Once you get beyond that, the performance starts going back more toward straight ethylene glycol.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribune@gmail.com.