If you hear hissing, gurgling, or sizzling noises from your engine or exhaust, it may point to coolant leaks, exhaust leaks, or overheating issues. These sounds usually indicate fluid escaping, metal expansion, or pressure leaks. An inspection is essential to prevent costly engine or exhaust damage.

What does it mean if you hear hissing, gurgling, or sizzling noises?

These noises often mean hot coolant or fluids are escaping onto hot engine components, or gases are leaking from the exhaust system. They may also indicate that the cooling system is under too much pressure or has trapped air.

Common causes of hissing, gurgling, or sizzling noises

• Coolant leaks onto hot engine parts
• Exhaust leak at the manifold, gasket, or pipe
• Overheating engine causing boiling coolant
• Cracked radiator, hose, or coolant reservoir
• Loose or damaged serpentine belt (causing hissing)
• Leaking vacuum lines or intake manifold

Why do you need to fix this problem quickly?

Ignoring these noises can lead to overheating, loss of coolant, engine misfires, or exhaust system damage. Left untreated, these problems may cause engine failure, expensive repairs, or unsafe emissions.

How do you know when to get it checked?

You should book an inspection if:

• You hear hissing when the engine is running or after shutdown
• You see steam, smoke, or fluid leaks under the bonnet
• You smell coolant, burning oil, or exhaust fumes
• The temperature gauge rises abnormally
• The engine misfires or runs rough

What happens during an assessment?

A mechanic will:

1. Inspect the cooling system for leaks or overheating
2. Check hoses, radiator, and reservoir for cracks
3. Inspect the exhaust manifold, gaskets, and pipes for leaks
4. Listen for vacuum leaks in intake or hoses
5. Pressure-test the cooling system
6. Recommend necessary repairs such as gasket replacement, hose replacement, or exhaust repair

How much does it cost to fix?

Minor hose or gasket repairs may cost $150–$400. Exhaust repairs usually range from $250–$700+. Major cooling system or exhaust component replacements can cost $1,000–$2,500+ depending on the vehicle.

Is it unsafe to drive with these noises?

Yes. These sounds often signal coolant or exhaust leaks, both of which can cause engine overheating, reduced performance, or toxic fumes entering the cabin. The vehicle should be inspected and repaired immediately.