Why won’t my car’s engine warm up properly?

John Paul, AAA Northeast's Car Doctor, answers a question from a reader who just replaced his car’s engine.

AP Photo/David Zalubowski, File

Q. I recently had to replace the engine in my Toyota Camry. It had 234,000 miles, and the new engine has around 150,000. I’ve noticed that when it’s really cold, the car does not warm up when driving at highway speed. When it’s idling or going slow, the engine warms up fine. What’s up?

A. Start with a check of the engine thermostat. If the engine was sitting in a salvage yard for a while, the thermostat may be opening at too low a temperature. This would be most noticeable at highway speeds. If the thermostat is okay, then the problem could be air in the cooling system. This could be a result of a faulty head gasket, which is why the car could have been in the junkyard.


Q. I love my 1998 Volvo and plan to drive it as long as it will go. It has 223,000 miles on it. Volvo parts are really expensive, so I’ve been buying parts online. I’d like to understand aftermarket parts. Are there various qualities? Should I be asking for a specific manufacturer, given that I plan on keeping this car as long as I can?

A. I have no problem with aftermarket parts. That said, many replacement parts are equal to and in some cases may surpass the original equipment parts. Look for name brands from reputable parts stores such as NAPA. I have also had good luck with online parts retailers such as Rock Auto and CariD. When I’m shopping online, I tend to look for brand names that I am familiar with that will provide good service. As a general rule, if the replacement part is dramatically cheaper than the original equipment part, the quality may be questionable.

Q. I recently purchased a 2013 Nissan Pathfinder with 27,000 miles. I hear a knock from the engine that is fairly apparent until the car warms up for a minute or two. I took the car to Nissan and had someone drive and test it. They told me there are no trouble codes and the knocking noise is normal. Does my truck have a problem?


A. It’s not unusual to hear a slight knocking noise when the engine is cold. There is so much aluminum in engines today that parts will expand and contract as they warm up. As long as the noise goes away quickly I would agree with the dealer and call it normal.

Q. I have a 1999 Honda Accord and the service-engine light came on. The repair shop told me it was the evap system, but they couldn’t find anything wrong. They said the problem wasn’t on the fuel side. They reset the computer and all was well for almost three weeks. Then the light came back on. What exactly is the evap system and should I be concerned about the light?

A. The evap system is the term used for the evaporative emission control system, which prevents gasoline fumes from escaping into the atmosphere and causing additional pollution. Since 1996 most cars have had an onboard test of this system to ensure it doesn’t leak. Although in this case, the car’s performance will not change when the “check engine” light is illuminated, your car is causing air pollution. The most common cause of an evaporative failure is a loose or faulty gas cap.


Q. I heard somewhere that if many people share a car, it will wear out faster. We have three cars in the family. I think each person should drive their own car. The other two drivers feel they can jump into whatever is last in the driveway. Who is right?

A. This comes from an old adage and may be true – but to a point. When more people drive a car, no one takes responsibility for the preventive maintenance and minor repairs. Everyone thinks the other person took care of the oil changes, checking the tires, and other important issues. There is no reason a car driven by several drivers should have a shorter life as long as someone takes responsibility for maintenance and repairs.

John Paul is AAA Northeast’s Car Doctor. He has over 40 years of experience in the automotive business and is an ASE-certified master technician. E-mail your car question to [email protected] Listen to Car Doctor on the radio at 10 a.m. every Saturday on 104.9 FM or online at


This discussion has ended. Please join elsewhere on