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Diagnosing a Grinding Noise From the Starter

Dan Ferrell writes about DIY car maintenance and repair. He has certifications in Automation and Control Technology and Technical Writing.


What May Cause a Starter Grinding Noise

A grinding noise from a car starter usually comes from:

  • A faulty starter diver gear
  • A faulty starter solenoid
  • An ignition switch that is sticking
  • A worn pinion drive gear, or
  • Loose mounting bolts on the starter motor

If You Hear a Grinding Noise During Startup

Usually, if there's too much clearance between the pinion gear and ring gear, the gears will produce a high-pitched whine while you try to start the engine. In this case, you may need to remove one or more shims from the starter, depending on your application. If your starter motor doesn't use shims, the pinion gear may have too much wear, and you will need to replace the starter.

If You Hear Grinding Noise After the Engine Starts

If there's not enough clearance between the pinion gear and ring gear, the starter may produce a high-pitched whine once the engine starts and you release the ignition to the "Run" position. If this is the case, you'll need to add one or more shims to the starter.

Other Reasons Your Starter May Be Grinding

A starter grinding noise means the starter pinion gear is not lining up correctly with the ring gear on the flywheel or flexplate. The two previous sections describe a couple of common sources of trouble leading to a grinding noise, but they are not the only causes.

You may need to check the clearance between the drive gear and the ring gear and compare it to the specifications in the repair manual.

The following sections list some checks you can do yourself to help you in your diagnostic and solve the problem sooner.

It's a good idea to have the vehicle repair manual for your particular model on hand. The manual will guide you in locating, removing, installing, checking and troubleshooting components. If you don't have this manual yet, you can buy a relatively inexpensive copy through Amazon. Haynes manuals come with step-by-step procedures, images and photos for many maintenance, troubleshooting, replacement parts projects; torque values for mounting bolts, electrical diagrams, plus correct electrical voltage and resistance values for many electrical components you may need to check.

The pinion gear is a common source of trouble.

The pinion gear is a common source of trouble.

How to Begin a Starter Motor Check

A starter motor can last for years. However, during its years of service, one or more problems may develop, hindering starter motor operation. Depending on the particular issue, you may be able to do some adjustments and keep your current motor in service. Here are some things you may want to look into.

Before you start, you may need to do some preparation.

  • Depending on your particular model, you may need to raise the front of the vehicle to gain access to the starter motor. If necessary, use a floor jack and support the vehicle on jacks stands. Never work under a vehicle supported only by a floor jack! The vehicle may fall on you while working on it.
  • Other models have the starter motor mounted on the upper area of the engine. So you may need to remove one or more components to gain access to it.

Preliminary checks:

  • Make sure the starter motor mounting bolts are tight; try to rock the starter back and forth by hand.
  • Remove the starter motor and check the starter drive mechanism.
  • Check the ring gear on the flywheel or flexplate. Although damage to the ring gear is rare, it's possible.
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To check the ring gear, you'll need to rotate the engine by hand. To do this, after removing the starter motor and, if necessary, having the vehicle supported on a jack stand:

  • Set the transmission to Neutral (manual) or Park (automatic).
  • Engage the emergency brake.
  • Use a breaker bar to rotate the engine clockwise by turning the center bolt on the crankshaft pulley, in front of the engine.
  • Have an assistant check the ring gear as you turn the engine.

In some cases, removing the spark plugs makes it easier to rotate the engine.

If everything seems right, have the starter motor checked. Usually, auto parts stores will test your starter motor free of charge.

Other Not-So-Common Sources of Grinding Noise

There could be other, less common reasons for a metal-on-metal grinding noise coming from the starter motor as you try to fire up the engine.

  • faulty starter drive gear (sticking overrunning clutch, damaged gear teeth)
  • damaged flywheel ring gear
  • damage to the starter drive-end housing
  • sticking ignition switch
  • bad starter solenoid

If you haven't found the source of the problem causing your starter motor to grind, have the starter motor checked at your local auto parts store.

Video: A Starter Motor Fails and Starts to Grind

In the following video, from Western Wyoming Community College, you can hear how a starter motor grinds during cranking. Watch the clues that were there about the problem, and the source of the grinding noise.

How to Install a New or Remanufactured Starter Motor

If you need to replace the starter motor, follow these simple recommendations to make sure the pinion and ring gears engage properly.

  • Often, a new or remanufactured starter motor will come with an aluminum-painted housing. In this case, sand away the paint at the mounting surface.
  • Install the shims and heat shield that come with your application. The shims are necessary for the proper clearance between the drive gear and the ring gear. Without them, the gears will clash and grind.
  • Start the mounting bolts by hand to make sure they fit properly.
  • Make sure to seat the starter motor properly.
  • Tighten the screws to the torque listed in your repair manual.
  • If possible, pull the pinion gear using a screwdriver and verify that the gear comes out and meshes properly with the ring gear.
  • Your repair manual may list the correct clearance between the gears. Use a feeler or wire gauge to measure clearance. You may need to add or subtract shims.
  • Make sure all electrical connections are clean and tight.

Starting System Diagnostic Resources

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2022 Dan Ferrell

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