Why does my car make a moaning sound?

John Paul, aka “the Car Doctor,’’ answers readers’ car-related questions.

By John Paul

November 10, 2015

4 minutes to read

Q. My 2012 Mercedes GLK has started to make a sound on the front left when I’m making a right. It initially sounded like a tire deflated, but tires were fine. Now it sounds like moaning. Do you have any advice for me?

A. There are several possibilities such as a wheel bearing failure or even debris caught up in the brake system. I would start by taking a technician for a ride so they can hear the same sound you are hearing. One other possibility Mercedes released a technical service bulletin regarding a similar noise that could come from stress on the drivetrain and exhaust system. The fix is repositioning various components to eliminate the noise.

Q. I would like your thoughts on an accident that happened this past summer with my 2012 Toyota Prius. I “parked’’ my car and while the vehicle was still on, I hopped out of the driver’s seat in order to get to something that was in the back seat. I found the passenger door locked and while I was still outside the car jerked and began to roll backwards and came to a stop at the bottom of a hill. My insurance agency after doing some research discovers that the Prius park system/button does not operate the same way as a mechanical gear shift lever. My questions to you are: have you heard of similar accidents with the Toyota Prius, should Toyota be doing something about this, either by changing their park system in the vehicles, or, at the very least, informing customers about how to use it? My third question is should I appeal my insurance surcharge?

A. The Prius like many cars today use a pretty sophisticated “park’’ system. When the park button is selected a signal is sent to the car’s computer. The car’s computer determines if park is possible (the car isn’t moving) and activates the parking mechanism which is a mechanical lever inside the transmission. Although I haven’t heard of any incidents with a failure of the system it is easy to see how the car may not go into park when the button is pushed and the car is still on. Some car makers will automatically engage park when the ignition is switched off -some do not. I have done the same thing only to realize the car was still in gear. Regarding should Toyota inform their customers, they do. In the car owner’s manual it states when parking the vehicle Stop the vehicle completely, set the parking brake, shift the shift position to P and check that the shift position indicator shows P. Most new car owners never read the owner’s manual. Regarding the insurance I would challenge the surcharge—the people at the hearing are just like you and me and may have some level of sympathy for what happened.

Q. I have a question regarding my 2013 Honda CRV, the other day while it was raining very hard I put on my hazard flashers, my entire dash, radio and GPS screens went blank. After arriving home I shut things down started up again and all was normal. I cannot duplicate it again. I called the Honda dealer and they stated for them to work on it, they would need to see the system not working. Any suggestions would be helpful and should it get it on record so that if I go out of my warranty it might be covered? Do you know of any updates to the system that might address the issue?

A. The dealer is correct that they can’t fix something that isn’t broken. That said I would certainly have the dealer look at it while it is under warranty. If it does fail after the warranty expires perhaps you can get some assistance from Honda with the repair. There are no specific technical service bulletins but quite a few that address issues with the GPS system. This to me indicates a higher than normal level of failure. It could be a fluke and never happen again but it certainly worth noting in case it happens in the future.

Q. I drive a nice 2003 Toyota Camry that only has 55,000 miles on it. Can you tell me if I am damaging or incurring excess wear on my transmission by shifting down and let the engine do the braking rather than using (and saving) the brakes. I like to drive this way but my friends tell me it is not a good idea, if not why?

A. In my opinion it is much cheaper (the cost of brake replacement versus a transmission overhaul) and more efficient to uses the car’s brakes rather than the transmission to slow the car. The internal bands and clutches of the automatic transmission in your Toyota are not designed for manual down-shifting. Years ago it made more sense to down shift because vehicle brakes were not very good and would easily overheat and be prone to brake fade. Today with disc brakes this is not the case.