Grinding noise after starting the engine: causes and solutions

The sharp and unpleasant metallic sound heard when the ignition key is turned can scare even an experienced driver. If you hear grinding noise after starting the engine, this is a sure sign that a serious malfunction has occurred in the starting system or gas distribution mechanism. Ignoring such sounds can lead to costly repairs, as parts subject to friction and shock loads are destroyed exponentially.

Most often, the source of the problem lies in the elements that provide primary rotation of the crankshaft. This could be a worn bendix, a damaged flywheel crown, or problems with the timing drive. Diagnostics requires careful attention to the nature of the sound: is it short-term or constant, does its tone change as the engine warms up. In this article we will analyze in detail the main causes of extraneous noise and methods for eliminating them.

You should not rely on “maybe” and continue to operate a car with such a malfunction. Metal shavings formed as a result of friction can get into the oil passages, which will lead to failure of the plain bearings. Timely identification of the cause of the grinding noise will save your budget and nerves.

Diagnostics of the starter system and bendix

The most common reason for being handed out grinding noise when starting the engine, is a malfunction of the starter, and specifically the overrunning clutch, popularly known as Bendix. This unit is designed to transmit torque from the starter motor to the flywheel and automatically disengage the gear after the engine has started. If the mechanism jams or the gear teeth wear out, slipping and a characteristic clanging noise occurs.

To understand whether the problem lies here, you need to listen to the moment the ignition key is released. If the grinding noise stops immediately after you release the key, but the engine continues to run smoothly, then in 90% of cases the bendix is ​​to blame. It is also worth paying attention to solenoid relay: if it does not feed the gear energetically enough, engagement with the flywheel ring occurs with impact and subsequent noise.

• 🔍 Visual inspection: Remove the starter and check the condition of the drive gear - the teeth should not be licked or chipped.
• 🔧 Check progress: The Bendix gear should rotate freely in one direction and jam in the other; any play in both directions indicates a breakdown.
• 🛢️ Lubrication: Sometimes the reason lies in dried grease in the starter gearbox, which makes it difficult for the gear to come out.

⚠️ Attention: Prolonged operation of a car with a faulty bendix will lead to “licking” of the teeth not only on the starter, but also on the flywheel crown, the replacement of which requires removing the gearbox.

Repairing the starter is often more expedient than buying a new unit, especially when it comes to a high-quality overhaul with the replacement of bushings and bearings. However, if the starter housing is cracked or the winding is burned out, it is better to replace the entire unit. Remember that electric current in the starter reaches hundreds of amperes, so the contacts must be perfectly clean.

It is also important to check the attachment of the starter itself to the cylinder block. Loose bolts can cause misalignment, causing the gear to not engage fully, causing a loud grinding sound as it rotates.

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Problems with the flywheel ring

The flywheel crown is a steel toothed ring pressed onto the engine flywheel. It is with this that the starter gear interacts. Over time, especially with frequent starts or problems with electrical equipment, the teeth of the ring can grind down, break or become deformed. If rattling sound on startup is chaotic in nature and accompanied by vibration, there is a high probability of damage to this particular element.

The difficulty of diagnosis lies in the fact that the flywheel crown is hidden from view and is located between the engine and gearbox. To inspect it, the gearbox must be dismantled, which is a labor-intensive procedure. Often drivers change the starter, thinking that the problem is there, but the grinding noise returns as the new bendix gets into the damaged areas of the ring.

There are several signs indicating wear on the crown:

• 📉 Unstable startup: The starter turns, but engagement does not occur the first time, accompanied by a clanging sound.
• 🔊 Sound change: The grinding noise may intensify in certain temperature conditions or after a long period of parking.
• ⚙️ Visual defects: When the gearbox is partially removed, “licked” or missing teeth on the ring are visible.

If only a few teeth in one sector are damaged, some craftsmen practice welding and surfacing of missing sections, but this is a temporary solution. The most reliable method is to replace the crown. On some modern cars, the crown is part of the flywheel, and it has to be replaced as an assembly, which significantly increases the cost of repairs.

When assembling after replacement, it is extremely important to set the marks correctly and ensure uniform heating of the crown before pressing to avoid distortions. Unprofessional installation may result in flywheel runout, causing vibration and accelerated wear. crankshaft and support bearings.

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Timing chain and gas distribution system

If a grinding or metallic noise is heard not only at the time of startup, but also in the first seconds of engine operation, until the oil pressure rises, the problem may lie in the gas distribution system. In engines with With a timing chain drive, wear on the tensioner or the chain links themselves leads to sagging. When starting, the chain hits the walls of the casing, producing a characteristic rumble, which is often confused with the grinding sound of the starter.

⚠️ Attention: A broken timing chain on most modern engines leads to bent valves and a major overhaul of the cylinder head. If suspicious sounds appear in the circuit area, operation should be stopped immediately.