Diagnosing Engine Squeals: A Triage Guide to Belt vs. Pulley vs. Leak | MyMechanic
The Three Main Suspects
When an engine squeals under load, it's almost always related to the serpentine belt system. The load from an accessory (like the power steering pump or A/C compressor) is causing something to slip or strain. The three main culprits are:
The Belt Itself: The belt is worn, glazed, or contaminated and is slipping on a pulley.
A Failing Pulley/Bearing: The bearing inside an accessory or pulley is failing and starting to seize, causing the belt to drag and slip over it.
A Fluid Leak: Power steering fluid or coolant is leaking onto the belt, lubricating it and causing it to slip.
Triage Step 1: Analyze the Squeal
Suspect #1: The Belt
The Sound: A high-pitched, sharp squeal. It may be brief or last as long as the load is applied.
The Trigger: Happens on cold starts, in damp weather, or when turning the steering wheel sharply or turning on the A/C.
The Diagnosis: This points to a belt that is hardened (glazed), cracked, or has a weak tensioner. The belt itself is slipping on the pulley.
Suspect #2: A Failing Pulley Bearing
The Sound: Often more of a constant whirring, whining, or grinding noise that gets LOUDER and more intense when the load is applied. The underlying grinding noise may be present even without the load.
The Trigger: The noise gets significantly worse when you load that specific accessory. For example, if the power steering pump bearing is failing, the grinding will intensify when you turn the wheel.
The Diagnosis: The bearing inside the accessory is failing. The load is making the failing bearing work harder, creating the noise.
Suspect #3: A Fluid Leak
The Sound: A loud, often continuous squeal as soon as the engine starts. It may be accompanied by visible fluid drips.
The Trigger: The noise is constant because the belt is continuously contaminated by the leaking fluid.
The Diagnosis: A visual inspection is key. Look for signs of fluid (oily power steering fluid or colored coolant) on or around the belt and pulleys. A leak from the power steering pump is a common cause.
Frequently Asked Questions
Conclusion
By playing detective and analyzing when the squeal happens and what it sounds like, you can make a very educated guess about the root cause. This helps you communicate effectively with a technician. For Singaporean drivers in Malaysia, being able to tell your mechanic "it squeals when I turn the wheel" is good, but saying "it sounds like the belt is slipping whenever the power steering pump is loaded" is even better. It leads to a faster diagnosis and repair from a trusted service like MyMechanic.
Need Roadside Assistance?
While this guide can help you narrow down the cause, a definitive diagnosis requires a trained ear and a professional inspection. For Singaporean drivers in Malaysia, MyMechanic can provide an expert on-site assessment to pinpoint the source of the squeal and recommend the correct repair.
