Questions and answers from the ‘Car Doctor’

Q. I have taken my 2012 Toyota RAV4 into several mechanics over the past several months. My car now upon acceleration makes a “grinding” noise between 3540 MPH, it goes away when I take my foot off the gas and then after 40 there is no other issues. I have had the oil changed every 3-4 months, transmission fluid changed, new brakes and pads, new tires, new hoses for the coolant and replaced oxygen sensors. The car does have 175,000 miles on it, and I bought this car in 2015 with 18,000 miles. The shops cannot figure out the noise and the check engine/4wd/ TRAC light stays on even after they “fix” it. Very frustrated with no solution, any thoughts about these issues?

A. The grinding noise could actually be a vibration from a rusted-out exhaust heat shield. At certain engine speeds there will be a vibration, and this can cause the shields to vibrate and sound like a grinding noise. If the noise is in the rear of the car, the most likely issue is a rear bearing, although that is more of a growl than grinding noise Regarding the check engine light and 4WD and TRAC lights these are usually caused by a faulty wheel sensor or other part that is causing both the check engine light to come on and at the same time disabling the 4WD system. The first step is to read the codes and look at some data. Perhaps even go to an auto parts store that offers free code reading. If the code repeats a couple of times, recording the code (s) should help the repair shop with the diagnosis and repair.

Q. I own a 1962 Chevy Nova. It had a 6-cylinder that I changed to a 283 cubic inch 8-cylinder engine. It ran fine and now It started overheating. The heater core leaked so I capped it off, I do not drive it in winter, so heat is not necessary. The new upper radiator hose blew off the thermostat housing. I never changed the radiator when I changed the engine. Any suggestions of overheating cause? Should I first start with changing to a bigger radiator?

A. I would start with all the basics first. Check the thermostat for proper operation, are there cold spots in the radiator when the engine is hot that could indicate a clogged radiator? What cooling fan are you using, is it upgraded to electric or are you using a clutch fan? In either case it may not be working as the engine gets hot. Although not common on a 283 cubic inch V-8, a head gasket could be the issue. As for the radiator, the 6-cylinder radiator has a core that is about four inches smaller than a typical V-8 radiator, so certainly it would provide better cooling. But the idea, it was fine for a while, tells me there is something else going on.

Q. My 2011 Pentastar engine in my Jeep Grand Cherokee, has 172,000 miles on it and runs quite well still. I believe frequent oil changes contributed to this longevity, as well as a well-engineered motor. Since 90,000 miles noth

ing major has been done. My question is, is there any service I can perform at this stage to stay ahead of a problem?

A. Keep doing what you are doing, oil changes with quality oil and filters, using the correct grade of oil. Easy on the engine (light acceleration) until it fully warms up and regular coolant service and checks of other vital fluids. Look for changes in oil use and miles per gallon, both can be an indicator of something going wrong before it actually happens.

Q. I am not criticizing, but maybe I am. I have owned a repair shop for 30 years and sometimes a customer will bring us a car that has been to multiple shops and not repaired. We may spend several hours finding the problem and then it could be several more hours, if not longer, to repair it. How can you do this without even seeing the car?

A. My advice column is just that, advice based on research and personal experiences. I carefully read the question, do not jump to conclusions and research technical service bulletins using Alldata as well as repair forums to come up with an answer. Also, I try to provide a consumer based second opinion. I am not going to tell someone how to rebuild an engine in a 50-word response but will give an opinion if the engine needs rebuilding.

Q. I listen to your podcast each week but last week there was not one posted (johnfpaul.podbean.com). Was the problem on your end or mine? I hope you have not given up the podcast, I enjoy it.

A. The live radio program, which later becomes the podcast, was preempted for a local hockey game. These local high school kids got to the playoffs and were playing at the legendary Boston Garden. Thanks for listening, the Car Doctor program is live on Sunday at 11 on www.959watd.com and the podcast is usually posted by Monday. Thanks for listening.

Q. I just purchased a used Hyundai Tucson, which is still under the warranty. The dealer said that since the is a Certified-pre-owned vehicle I need to come back to the dealer for service to maintain the warranty. I really like this car and want to keep it for a long time, but I have built up a great relationship over the years with my own mechanic. If my mechanic uses Hyundai parts will that maintain the warranty? I don’t want to void the 100,000mile 10-year warranty.

A. What makes this car different than other used Hyundai models is that it is a Certified Pre-owned vehicle. Typically, when a second owner purchases a Hyundai the warranty reverts to a five-year 60,000 mile warranty. As a CPO vehicle it keeps the 10-year 100,000 miles drivetrain warranty. Perhaps you misunderstood the dealer. You only need to maintain the car in accordance with the owner’s manual to maintain the warranty. As long as you keep records and use quality parts your car will be covered under the warranty.

Got a car question, email the Car Doctor for a personal reply. jpaul@ aaanortheast.com