What Causes Abnormal Noise During Cold Start?
2 Answers
The reasons for abnormal noise during cold start are: 1. Hydraulic tappet; 2. Valve clearance; 3. Dirty throttle valve; 4. Operating sound of carbon canister solenoid valve; 5. Three-way catalytic converter; 6. Timing components; 7. Friction noise from air conditioning belt; 8. Malfunctioning fuel tank vent valve; 9. Fluid impact inside recirculation pump; 10. Partial blockage in fuel filter. The reasons for high idle speed during cold start are: 1. Throttle valve sticking or not closing properly; 2. Faulty idle control valve; 3. Malfunctioning coolant temperature sensor; 4. Air intake system leakage; 5. Faulty air conditioning switch or power steering pressure switch.
I've encountered this issue twice. That metallic squeaking sound during cold starts is most commonly caused by problems in the belt system. Especially for vehicles over five years old - the belt ages and hardens, the tensioner pulley bearings lack lubrication, or the idler pulley doesn't rotate smoothly, which becomes more noticeable when cold weather makes the rubber harder. Once I tested by spraying water on the belt with a spray bottle - if the noise disappears, it confirms belt slippage. If the sound comes from the bottom of the engine, it might be the clattering of a starter that doesn't retract promptly, particularly prone in winter. In such cases, replacement parts should be installed immediately, otherwise you risk damaging the flywheel ring gear which would be a much bigger problem.