Squealing noise on startup
A high-pitched squeal in the first seconds after a cold start that fades as the engine warms is almost always the auxiliary drive belt slipping on a pulley - because it is glazed, loose, wet or because a bearing in the tensioner or an accessory is dragging. A squeal that persists and changes with engine speed points to a bearing; one that appears when the A/C or steering load comes on points to belt tension. A brief metallic screech lasting under a second at the moment of start, on the other hand, is usually the starter pinion not disengaging cleanly.
Urgency
Visit a workshop soon
Possible causes, most likely first
- Glazed, cracked or contaminated drive belt
Squeal on cold start, in damp weather and under load, often with black rubber dust around the pulleys. Look for a shiny hard surface on the ribs, cracks more than a few per 10 cm, or oil and coolant contamination; a brief spray of water on the belt that quiets the noise confirms slip. - Weak automatic tensioner or wrong manual tension
Belt flutters visibly at idle and the tensioner arm bounces more than a few millimetres. On a manual adjuster, the belt should deflect about 10-15 mm under firm thumb pressure on the longest run; on an automatic tensioner check the wear indicator is within its marks. - Failing bearing in tensioner, idler or accessory
Squeal or chirp that does not go away when warm and changes pitch with RPM. With the belt removed, spin each pulley by hand: roughness, noise or wobble on the alternator, idler, tensioner, water pump or A/C compressor pulley identifies the culprit. - Misaligned pulley
Chirping at idle rather than a constant squeal, often after a water pump, alternator or tensioner replacement. Lay a straight edge across the pulley faces or use a laser alignment tool; more than about 1 mm offset causes rib-edge noise. - Power steering pump or alternator under heavy load
Squeal at start-up that worsens when the steering is turned to full lock or when all electrical loads are on. Low power steering fluid or a seized A/C compressor clutch can overload the belt; check fluid level and whether the compressor hub turns freely. - Starter pinion or ring gear wear
A short metallic screech only at the instant of starting, no noise once running. Inspect the ring gear teeth through the starter opening for wear or damage and check the starter mounting bolts are tight.
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What you can check yourself
- With the engine off and cold, inspect the belt ribs for a shiny surface, cracks or frayed edges, and look for rubber dust around the pulleys.
- Start the engine and note whether the squeal stops after a few seconds (belt slip) or continues and changes with revs (bearing).
- Turn on the A/C and turn the steering to full lock at idle: a louder squeal means the belt is slipping under load.
- Check the power steering fluid level if the car has a hydraulic pump.