What is the Grinding Noise When Starting a Car?

Jack R. Nerad | Jan 20, 2021

It is something many of us dread every time we turn the key or push the button to start our car. Instead of a short whir followed by the quiet rumble of the engine starting up, we hear a prolonged grinding noise. 

grinding noise when starting a car

Sometimes, after the banshee scream of the grinding noise, the car will start. Other times it won't, and it takes several turns of the key or pushes on the start button to crank the engine over and get it going. Of course, in the worst cases, the engine doesn't start at all. The ringing in your ears is the only evidence that you ever turned the key. This begs the critical question: what is the grinding noise when starting a car?

You need to know what causes the grinding noise you hear and what doesn't cause it. Further, we'll give you a way to tune-up your listening skills so you can begin to discern the mechanical problem you might be facing from the sound of the noise you hear. 

That is a skill that top mechanics have developed over years of hearing various noises emanate from the vehicles they work on, based on the consistent types of sounds various components make when they malfunction. Battery-related issues sound different than starter-related issues, for example. 

"Usually, when I hear the sounds the car makes in particular situations, I can get a pretty good idea of what's wrong," said Automotive Service Excellence-certified mechanic Eric Charles. "After a while, you just get a sense of these things."

What the Grinding Noise Isn't

When repairing all things mechanical, it is important to diagnose what is wrong before instituting a fix. If you fail to do that, you can end up spending good money to repair something that wasn't broken in the first place while at the same time not addressing the real problem and getting it solved. That is why it is essential to know what a grinding noise in a car probably isn't. 

For instance, to diagnose a problem properly, it is critical to differentiate between clicking noises, cranking noises, and grinding noises. All can occur when you turn the ignition key or push the starter button, but they have different causes and require different repairs.

When it comes to starting a car, battery issues can cause noises that might lead you to believe something is wrong with your starter when there isn't. Should you turn the key and hear a succession of clicks — tick, tick, tick like a loud and rapidly running clock — you do not have a starter problem. Instead, the likely cause is a weak, poorly charged battery or a loose battery terminal. 

Should you turn the key and hear the starter motor's cranking noise — a whirring sound like an electric motor turning — you do not have a starter problem either. In this case, the vehicle's battery seems fine because it continues to power the starter motor, but the engine doesn't start. This could result from several issues — lack of spark from the ignition system, fouled spark plugs, clogged fuel injectors, or a faulty fuel pump.

What the Grinding Noise Is 

If you hear a grinding noise when you turn the key or press the start button, you likely have a starter that needs replacement. 

One of the curiosities about a bad starter is that it can still start the engine. For example, it might take two or three turns of the key to get the starter to engage, turn the engine over and prompt it to start, but it will start the car. This can lead you to draw the faulty conclusion that it's okay and it will continue to start the vehicle. 

That's not the case. A starter that grinds is close to total failure, and you should replace it.

How Does a Car Starter Work?

It is instructive to know how a car starter works. A starter is essentially an electric motor that engages with the flywheel to turn the engine's crankshaft and get it operating. 

Before the invention of the self-starting engine, back at the dawn of the automobile age, drivers had to spin the crankshaft manually using a crank handle to start the car. This is analogous to pulling on the starter cord of a gasoline-fueled lawnmower engine or outboard motor to get it started.

To enable it to spin the flywheel, the starter has a small gear that engages with the ring gear on the flywheel to rotate it. An electric solenoid moves the starter gear on a Bendix drive to engage with the ring gear, and when the engine starts, it quickly disengages. 

Malfunctions in this system include misaligned gears, broken gear teeth, or even a poor solenoid that can cause the gears to clash. This generates the grinding noise when you push the starter button. It can sound similar to the grinding of gears in a manual transmission if the clutch is misused.

What to Do About the Grinding Noise When Starting a Car

While diagnosing the grinding noise problem when starting your car is complicated, the repair isn't complicated at all. In virtually all instances, the wise, cost-effective fix is to replace the starter. 

While it is theoretically possible to repair the Bendix drive, install a new gear, and/or replace the solenoid, for a lasting repair replacing the entire starter unit is the right thing to do. The good news is that replacing a starter is a common procedure that is not hugely expensive.

If there is damage to the ring gear on the vehicle's flywheel, however, the news isn't as good. This is a time-consuming and challenging job because it most often involves removing the flywheel, which in itself is difficult.

Summary

So, what is that grinding noise you hear when starting a car? Most likely, if it is true grinding that you hear, the problem is related to the starter. Causes include the starter not lining up correctly with the ring gear on the flywheel, missing or damaged gear teeth, or a faulty solenoid. Replacing the starter is most often the right solution. However, if there is damage to the ring gear on the flywheel, the ring gear will need to be replaced.

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