Breaking in a brand-new engine not as laborious as it used to be

by Jim KerrBackyard Mechanic . Aug 31 2018

Question: I am about to purchase a new Toyota Corolla and this is my first new car. I was always told by my parents that I should break in the engine but they never told me how to do it. Can you tell me how I should drive to break in a new car?

— Sarah

Answer: Breaking in an engine is a process where the high spots on the moving metal parts of the engine are given time to wear smooth so the engine will last longer. Today’s vehicle powertrain parts are built to much more exacting specifications and the machining processes are more precise, so breaking in an engine is almost a thing of the past. There are still a couple things you can do to help prolong the life of your vehicle’s powertrain.

First, don’t run the engine at high rpm or idle it for long periods of time. Oil is the lifeblood of moving powertrain parts and when an engine idles, there is not as much oil splashing onto moving parts, so they get less lubrication. Also, high rpm-running places a higher load on parts and if there were high spots in the metal, they could shear through the oil film between the parts and cause metal-to-metal contact, which wears parts out.

Although you will not likely tow with your Corolla, pulling a trailer or hauling a heavy load should be avoided for the first thousand kilometres or so. You can tow from the start, but it does place more load on the engine.

I recommend you drive in a normal manner as you likely have been doing in previous vehicles. There are no special break-in procedures required for modern engines. However, I like to change the oil sooner than the first specified oil change. This gets rid of any wear particles, assembly dirt or lint captured in the oil during the first few hours of a new engine’s operation.

Question: I have a 2010 Dodge Caravan with a V-6 engine. When it is cold, it starts perfect but if I drive it and it is warm, it will not start. I have to wait 15 to 20 minutes, and then it will start.

I can hear the buzz from the fuel pump when the key is on and the engine turns over good. I had a new fuel pump installed a couple years ago. Could it be the pump again or is the computer giving wrong signals?

Answer: It sounds to me like you may have a flooding problem with your engine.

Cold engines need more fuel to start because most of the fuel condenses on cold engine parts, making it difficult to ignite. Warm engines cause the fuel to evaporate much quicker so less fuel is needed at start. Your engine starts well cold, so it should be getting more than enough fuel supplied by the fuel pump to start it warm. I suspect you have a different problem.

The first thing to check is the temperature-sending unit. If the sender is out of calibration, it can be telling the computer your engine is cold all the time. You would notice hard starting when warm and very poor fuel economy because the computer is injecting too much fuel.

The fuel injectors should also be checked to see if they are leaking. If an injector leaks when the engine is off, it allows liquid fuel to flow into the manifold. The engine then floods when it is started and the spark plugs foul. After the engine sits for several minutes, the fuel has a chance to evaporate inside the cylinders and the engine starts when you crank it.

Next, check the ground connections between the battery, the body and the engine. I have experienced hard starting several times on warm vehicles that was cured when the ground connections were cleaned and tightened. A bad ground affects the computer control and sometimes the computer will inject excessive amounts of fuel on warm starts, flooding the engine.

Finally, pressing the accelerator pedal all the way down signals the computer to turn off most of the fuel injection during cranking. Try this when starting your vehicle warm. If it starts, then you know you have a problem with too much fuel in the engine.