What happens if you don't shim your starter?

Failing to shim your starter motor correctly causes misalignment between the starter's drive gear and the engine's flywheel (or flexplate). This improper gear mesh will result in a loud, high-pitched grinding or whining noise when you turn the key. If left uncorrected, it will quickly strip the teeth off both gears and ruin the starter housing, leading to expensive repairs.

Do all starters need shims?

No, not all starters need shims. Shims are primarily used to adjust the gap between the starter gear and the engine flywheel so they mesh perfectly without grinding. Whether you need them depends heavily on your vehicle's make, model, and the specific installation.

What can you use instead of a shim?

Depending on your specific application, common everyday items like playing cards, washers, zip ties, and scrap wood make excellent, sturdy alternatives to traditional shims.

What are the risks of shimming?

Essentially, shimming is the new skimming. Shimming devices are more challenging to detect since they are so much smaller than skimming devices, but the result can still be the same: card fraud and the risk of bank information/access being exposed.

Why is my starter not grabbing the flywheel?

A starter typically won't grab the flywheel because the electrical supply is dropping, the moving gear is jammed, or the teeth are physically stripped.

How To Install & Shim a Starter

Can I make my own shims?

Yes, you can absolutely make your own shims. Depending on your project, you can easily craft them out of scrap wood, cardboard, or playing cards using basic tools like a saw, utility knife, or scissors.

Is a shim kit necessary?

On most of the newer cars, these brake shims are mainly used to keep the noise down and any rattles to a minimum. Not all brake pads come with shims as they aren't required and function perfectly without needing them.

What are the disadvantages of shims?

While shims are highly effective for quick adjustments and leveling, they carry notable disadvantages. Depending on the application—ranging from carpentry to mechanics—using shims can introduce structural weaknesses, long-term deformation, alignment issues, and costly maintenance.

How do I force a starter to turn over?

To force a stubborn starter to turn over, the most reliable methods range from basic roadside tricks to direct electrical bypassing. First, confirm your vehicle is in Park (or Neutral for manual transmissions) and apply the emergency brake to prevent the car from unexpectedly lunging forward.

How do I know if my starter is bad or just the solenoid?

To determine if the starter motor or the solenoid is bad, you can perform a simple "screwdriver bypass test" on the two large metal terminals of the solenoid. If the starter motor spins when you bridge these terminals, the motor is good, and the solenoid is likely faulty. If it doesn't spin, the motor itself is the issue.

How to tell if a starter is engaging?

If you turn the key and hear one single loud click while lights remain bright, that is a sign that the starter relay is engaging but the starter motor does not turn the engine over. A starter that is worn or failing may make grinding or whining noises when engaging.

When replacing a starter, why is shim placement important?

Located between the mounting pad of the starter motor and the engine block, the starter shim is a thin, flat piece of metal. It ensures the correct spacing between the starter motor and the ring gear on the flywheel or flexplate. Improper spacing causes misalignment and can lead to starter failure or flywheel damage.

Can O'Reilly's test a starter?

Yes, O'Reilly Auto Parts tests starters for free. You can either bring in the starter once it has been removed from your vehicle, or bring the entire vehicle to the store. Their team will test the starter on a bench-top machine to determine if it is failing.

Do you always have to shim a starter?

No, not all starters need shims. Shims are primarily used to adjust the gap between the starter gear and the engine flywheel so they mesh perfectly without grinding. Whether you need them depends heavily on your vehicle's make, model, and the specific installation.

What to use instead of a shim?

What you can use as a shim depends on what you are trying to adjust, but everyday household items like folded cardboard, playing cards, metal coins, or cut-up plastic bottles make excellent temporary shims.

Are shims necessary?

Brake shims are an important component in the braking system that help absorb vibration and reduce noise, leading to a quieter and more enjoyable driving experience. Attached to the friction pad backing, brake shims provide a barrier between the brake pad and the caliper, helping to prevent small vibrations.

Can cardboard be used as a shim?

These cardboard shims are practical and convenient, which will save you from using more mud and sanding if you do the work upfront with them. They help to straighten uneven wall studs or joists to create a level, straight, and flat surface for installing drywall.

What tool is used to cut shims?

Answer. A hand saw or a utility knife is commonly used to cut wood shims. For more precise cuts, especially when dealing with thicker shims, a miter saw or circular saw can also be employed. Always ensure that the cutting tool is sharp to achieve a clean cut.

Why is my starter whining but not engaging?

A whirring starter that fails to crank your engine typically points to a faulty starter solenoid, a broken Bendix drive, low battery voltage, or stripped flywheel teeth. The starter spins, but the mechanism extending the gear into the engine is failing.

How to bypass a bad starter solenoid?

When a vehicle fails to start due to a suspected faulty starter solenoid, it is important to prioritize safety. Attempting to bypass a solenoid by bridging electrical terminals with metal tools can cause dangerous sparking, electrical burns, or even a battery explosion. Furthermore, if the vehicle is not properly secured, it could move unexpectedly and cause injury.

How to tell if a flywheel is seized?

A seized flywheel is a severe mechanical failure where the engine's flywheel locks up completely or cannot rotate freely. Symptoms include a complete inability to crank or start the engine, a grinding noise when trying to start, broken starter teeth, or the engine stalling abruptly and refusing to turn over.

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