Q: Where is the outdoor temperature sensor on a car generally located? I ask because it appears that the temperature indicated on the dashboard does not always align with the ambient temperature. If the sensor is located under the hood, would the heat reflected from the hood elevate the true indicated temperature?
T.A., Coral Springs, Fla.
A: The outside air temperature sensor may be located in different places, but generally it is behind the front bumper so that engine heat has no influence. Still, it can be affected by the heat of the pavement, especially when sitting in traffic. You may also notice that the temperature changes slowly. That is by design to prevent wild swings as you drive.
Q: What are jake brakes? Why are they so loud? Can anything be done without compromising safety?
P.B., Lehighton, Pa.
A: Short question, but longer answer. Developed by Jacobs Vehicle Systems, it converts the engine from a power producer to a simple air pump. Air comes in through the intake valves and, instead of being compressed and ready for the power stroke, that air is expelled via the exhaust valves, which open before compression can occur.
The sound is not unlike a musical instrument, a trombone for instance, vibrating air pulses out of the bell end. Jake brakes save fuel and allow the truck to slow down with less use of the service brakes. Prohibiting engine braking in populated areas is currently the only option for reducing the noise.
Q: I read with both heightened interest and a smile the letter about keyless ignitions allowing us to forget the engine is running. Seems C.L. of Chicago has a GM car and can lock it while it is still running. My wife has a 2014 BMW X3 SUV. I have A 2018 Audi A4 sedan. Neither will allow this to happen. If we try to lock either of our cars while it is still running, the car will immediately stop as soon as we press the “Lock” button on our remote.
P.F., Orland Park, Ill.
A: It is still possible to leave the car running in your garage if you don’t lock the doors. GM car owners and others with OnStar can call and have the doors unlocked remotely if they leave the key fob in the cup holder. Beginning with the 2020 model year, Toyota is equipping some of its vehicles with automatic shut off (and automatic park engagement). This feature will automatically shut off the engine after a predetermined period of time. Future enhancements will include smartphone apps as an added reminder.
But no technology eliminates the need for motorists to be responsible for their own safety. Keep involved with the task of operating your car.
Q: Recently, I solved a midlife crisis and test drove the Ford Mustang, Chevrolet Camaro and Dodge Challenger. After purchasing the Challenger, a car with hemi and manual six-speed transmission, I am totally happy. With that said after three months and weekly washing and detailing I noticed that the Mopar does not have a brake dust problem and the tires/rims are easily cleaned and require little detail work. Can you answer as to why?
W.G., Lake Worth, Fla.
A: The friction compound on brake pads is a lot like brownie mix. They may contain differing ingredients. Some brownies are cakey while others are chewy. Some are moist while others are dry. It is the blend of stuff that various 4-brake manufacturers use. Some are softer than others and some are dirtier than others. Softer materials often provide best feel for hard braking.
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 questions along with name and town to Motormouth, Rides, Chicago Tribune, 435 N. Michigan Ave., Fourth Floor, Chicago, IL 60611 or firstname.lastname@example.org.