Why Does My Car Make a Hissing Noise?

Ellie Dyer-Brown, 4 months ago

5 min read

  • Diagnostic
Hissing noise blog

WhoCanFixMyCar looks at some of the reasons why your car is making a hissing noise and what you can do to resolve it.

While there are many noises your car can make indicating something isn't right, hissing is one of the easiest to diagnose. This guide covers all the possible causes (and solutions) to help you understand what could be wrong with your vehicle.

Guide Contents:

Hissing noise from the engine

Hissing noise when accelerating

Hissing noise when the air conditioning is on

My engine is hissing

Engine overheating 

If you hear hissing coming from the front of your car, the engine may be overheating, especially if you can see smoke. Pull over in a safe place and allow your engine to cool down for at least fifteen minutes before investigating. 

Smoke coming from an overheating engine

Low coolant is one of the most common causes of overheating, so the first thing to look at is the fluid level in the coolant reservoir. If it's low, all you have to do is top it up, and you can be on your way. The exception to this is if you spot a coolant leak. A puddle of pink, blue, yellow or green liquid under your car is a clear sign of a leak.

The average cost to fix a leak in your car is around £77.38.

Another possibility is that you have a vacuum leak, defined as anything behind the mass air flow (MAF) sensor allowing air to enter the engine. You might be able to locate the leak yourself, but for a long-lasting fix, it's best to book a professional repair.

My car makes a hissing noise while accelerating

Damaged cooling system

Cooling system issues often cause hissing sounds, mainly when the problem is related to hoses. These are made of highly flexible rubber designed to withstand engine vibrations, high-pressure coolants, high temperatures and oils. Over time, they deteriorate, and when this happens, it can lead to fluid leaks.

Mechanic holding an engine hose.

However, if you hear a hissing sound, it’s probably the sign of a vacuum leak, especially if your check engine warning light comes on and your car seems to be idling faster than usual. 

General engine warning light repairs cost around £64.42.

Exhaust leak

Exhaust Repair

If your exhaust manifold or pipe is damaged, this can also cause a hissing sound. Exhausts play an important role in guiding harmful gases away from the interior of the car, so you should get any leaks fixed as soon as you can for the sake of you and your passengers.

The average cost of exhaust repairs is around £112.67 according to our data.

My car makes a hissing noise when the air conditioning is on

Leaking valve

The compressor in your air conditioning has a valve that often makes a hissing noise if it starts leaking. Valves help to keep the refrigerant gas pressurised; if you suspect yours is failing, book your car in to have its air conditioning system serviced. The pressure inside the compressor may be too high, which is serious. 

If your car is making a hissing noise, even if you think it might be nothing major, you should always get it checked out by a professional. 

If you have any other issues with your car that you'd like to try to diagnose yourself, check out our guide on self-diagnosing car problems. The more you know about how your car works, the better.

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Written by Ellie

Ellie Author Pic

Ellie is WhoCanFixMyCar’s Content Writer. She has a BA in English literature from Durham University, a master’s degree in creative writing, and three years of experience writing in the automotive industry. She currently drives a Suzuki Swift.

Find Ellie on LinkedIn.