A car that got louder overnight almost always means an exhaust leak, a worn bearing, or a tire issue. Here are the most likely causes ranked by how often they actually turn out to be the problem.
A cracked manifold or rusted-through pipe makes a deep rumble or ticking that gets louder under load. Most common on cars over 10 years old.
A bad bearing makes a constant humming or growling that changes with speed and disappears when you turn one way. Often confused with tire noise.
Tires worn unevenly create a roaring or thumping noise that rises with speed. Rotate hand over tread - if it feels like sawteeth, that is the cause.
A loose heat shield rattles like a tin can, especially at idle or low RPM. Cheapest fix on the list - often a $5 hose clamp.
A squealing, chirping, or whirring under the hood points to a serpentine belt or tensioner pulley. Worse on cold starts.
You smell exhaust fumes inside the cabin, hear a metallic grinding while braking, or feel vibration through the steering wheel. CO leaking into the cabin can be deadly.
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A clamp or hanger is $50-$150. A flex pipe weld is $150-$300. A full exhaust manifold replacement runs $400-$1,200 depending on the engine.
Short term, yes, if you do not smell fumes in the cabin. But unburned hydrocarbons and carbon monoxide can leak in, so get it fixed within a week or two.
Exhaust leaks open up under engine load. A small crack in the manifold or a missing donut gasket gets louder as exhaust pressure rises.
Yes. A bearing that fails completely can let the wheel wobble or even separate. Replace it within a few hundred miles of noticing.
If your tires are cupped or worn unevenly, yes - sometimes dramatically. New tires can drop cabin noise 5-10 dB.