Anything in your car that sounds, smells and looks abnormal should be checked. However, many people will tend to ignore the minor signals that often indicate a looming problem. For instance, some car owners will not react to a flashing check engine light. After all, the blinking light will disappear after some time. The check engine light and other dashboard lights indicate that your car needs immediate attention from a professional mechanic.
I've been running an auto service shop for the past 30 years. The trends in cars have changed a lot over that time, and cars are becoming a lot more complicated and automated. People can't fix many items on their own cars any more as you need a computer to diagnose most issues. People use their cars a lot more these days as we live further away from workplaces and schools so it's important for me to be able to get cars back quickly. I have had to keep learning about how the new cars run and I keep a lot of hints on this site so you can all learn the things you can do to make your cars run better.