Decoding the Hissing Sound from Your Engine After Turning Off: 8 Common Causes and Solutions!

Published:

Updated:

Author:

hissing sound from engine after turning off

Disclaimer

As an affiliate, we may earn a commission from qualifying purchases. We get commissions for purchases made through links on this website from Amazon and other third parties.

Picture this – you’ve had a long day, and you’re finally back home. You turn off your car, and then it starts – you hear a whining noise when revving the engine in neutral or a hissing sound after stopping the engine.

If you can relate to this scenario, I’ve been there too. The hissing sound from your engine usually occurs due to cracked hoses, a defective pressure cap, vacuum leaks, or a leakage in the cooling system.

But there can be other causes as well. Troubleshooting your vehicle’s hissing noises is a tough task. But fear not, I’m here to break it down for you. Today, I’ll take a deep dive into what a hissing sound from your engine means and what might be causing it. Let’s find out!

hissing sound from engine after turning off

8 Common Causes and Probable Solution of a Hissing Sound from Engine After Turning Off

There could be various reasons for weird sounds, such as a chirping noise from the engine when cold or hissing sounds from the engine. Here are some of the most common reasons:

1. Leakage in the Cooling System

The cooling system keeps your engine at the optimal temperature by circulating a liquid coolant through the engine and the radiator.

If there is a leak in any part of the cooling system, such as the hoses, pipes, radiator, water pump, or thermostat, it can cause your engine to overheat. Thus, it can create a hissing sound as the hot coolant escapes from the leak.

Solution

To fix this problem, you need to find and seal the leak as soon as possible.

You can use a pressure tester to check for any leaks in your cooling system. You can also use a flashlight to look for any visible leaks, cracks, holes, or burns on your cooling system components under the hood.

If you find a leak, you can try using a coolant leak sealant to temporarily stop it until you get a new part. This will likely cost you anything between $8 to $20 (the cost of leak sealant).

2. Vacuum Leak

A vacuum leak occurs when there is a crack or hole in any of the hoses or pipes that carry air into or out of your engine.

This can cause a loss of pressure, performance, fuel efficiency, and emissions control. It can also hear a hissing sound as air escapes from the leak.

Solution

A vacuum gauge can be utilized to examine for any leaks in your vacuum system. You can also use a spray bottle with water or carburetor cleaner to spray around the hoses and pipes while listening for any changes in the engine sound. If you hear a change, you have found the leak.

If you find a vacuum leak, you can try using duct tape or hose clamps to temporarily seal it until you get a new hose or pipe. This will cost you only $10 to $20 (the price of duct tape and hose clamps).

3. Issues with the Exhaust System

Another possible cause of a hissing sound from the engine after turning off is an issue with the exhaust system. The exhaust system carries the hot gasses from the combustion process out of the car through the exhaust pipe, manifold, muffler, and catalytic converter.

If there is a leak or a crack in any part of the exhaust system, it can create a hissing sound as the gasses escape from the leak or crack.

Solution

You can use an exhaust system pressure tester to check for any leaks in your exhaust system.

If you find an issue with your exhaust system, you should take your car to a mechanic for a professional repair or replacement. Depending on what part is causing the problem, this might involve welding, cutting, or bolting new parts onto your exhaust system.

The average cost of an exhaust system repair is between $150 and $800. It can vary depending on the complexity of the job. Replacing a muffler can cost around $100, a catalytic converter around $200, and an exhaust pipe can cost around $150.

4. Defective Pressure Cap

The pressure cap is a device that seals the opening of your radiator or coolant reservoir tank and maintains a certain pressure inside your cooling system.

If the pressure cap is damaged or worn out, it can fail to hold the pressure and allow coolant to boil and vaporize inside your cooling system. This can create a hissing sound as the coolant vapor escapes from the cap or the overflow tube.

Solution

You can use a pressure cap tester to check if your pressure cap is working properly or not. You can also look for any signs of damage or corrosion on your pressure cap and replace it if necessary.

The price of a pressure cap can vary depending on the brand, quality, and fitment. However, it’s likely to be anything between $8 to $12.

5. Low Level of Coolant Fluid

As already mentioned, the cooling system circulates a liquid coolant through the engine and the radiator.

If the coolant level is too low, it can cause your engine to overheat and create a hissing sound. It’s because, in that case, the hot coolant escapes from a leak or a crack.

Solution

To fix this problem, you need to check the coolant level in your reservoir tank and refill it if necessary.

The coolant level should be between the “minimum” and “maximum” marks on the side of the expansion tank.

In particular, it should always be at least 30% full. If the coolant level is below the “minimum” mark, top up the system with the recommended type of coolant until it reaches the “maximum” mark.

6. Malfunctioned Head Gasket

The head gasket acts as a seal between the engine block and the cylinder head, according to a 2015 failure analysis study. It stops the coolant and oil from combining and leaking into the combustion chamber.

Coolant or oil may leak into the exhaust manifold if the head gasket is damaged or broken. This will create a hissing sound as they sizzle and evaporate.

Solution

To fix this problem, you need to replace the head gasket as soon as possible. It involves removing and disassembling the entire engine and replacing other parts that might be affected by the leak.

Therefore, you should take your car to a mechanic for a professional diagnosis and repair.

The price of a head gasket can vary depending on the brand, quality, and fitment. But it’s likely to be around $25 to $170. The labor cost for this can be $200 to $500.

7. Cracked Hoses

Hoses are rubber tubes that connect various parts of your engine and carry fluids such as coolant, oil, fuel, or air.

Over time, hoses can wear out, crack, or break due to heat, pressure, or corrosion. This can cause fluids or air to leak out of the hoses and create a hissing sound as they escape from the cracks.

Solution

Look for any visible cracks, holes, or burns on your hoses under the hood. Additionally, check for any signs of leaks on the ground under your car as well.

You can use hose clamps or duct tape to seal any small cracks until you get new hoses temporarily. This will only cost you around $5 to $10 for the hose clamp and the duct tape.

By the way, replacing the old hose with the new one can cost around $150 to $170 including the labor cost.

8. Faulty Battery

According to a National Fire Protection Association report, if the battery is overcharged, damaged, or corroded, it can produce hydrogen gas. This gas can escape from the vents on the battery case and create a hissing sound as it reacts with oxygen in the air.

Solution

Examine your battery for any indications of deterioration or damage, and replace it if necessary. You should also check your alternator (it’s an electrical device that charges your battery while your car is running).

A battery replacement can cost around $500 and an alternator will take around $150.

You should also use a voltmeter to check the voltage output of your alternator and battery. If they are giving off wrong voltage readings, the only solution is to replace the battery and the alternator.

The normal voltage for most alternators should be between 13 and 14.5 volts when the engine is running. The normal voltage should be between 12.4 and 12.8 volts when the engine is off.

If the voltage is below 12 volts, it indicates a weak or dead battery that needs to be recharged or replaced.

Conclusion

Weird sounds from your car engine are never a pleasant experience. A hissing sound from your engine after turning off is surely a worrying ordeal.

But now that you know the possible causes and fixes, you’re well-equipped to take good care of your vehicle. Keep in mind that only regular maintenance and prompt attention to unusual sounds can help keep your engine in tip-top shape. Happy driving!

About the author

Leave a Reply

Your email address will not be published. Required fields are marked *