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Car Overheating Making Hissing Sound: Possible Reasons Why

Hi, I'm Azim Uddin, a student who loves cars. Visit to learn about car maintenance for beginners and experts. In my studies, I found a cool connection between hosting and car care. Join me on this journey where every road has a story, and hospitality meets the thrill of cars. Explore, learn, and enjoy the ride with me!

Hi, I'm Azim Uddin, a student who loves cars. Visit to learn about car maintenance for beginners and experts. In my studies, I found a cool connection between hosting and car care. Join me on this journey where every road has a story, and hospitality meets the thrill of cars. Explore, learn, and enjoy the ride with me!

Last Updated on May 10, 2024 by Azim Uddin

Car engines are prone to overheating, especially when the cooling system has an issue. When there are hissing sounds when it overheats, this shows a serious problem that requires fixing promptly.

But what are the possible reasons behind the car overheating and making a hissing sound? Coolant leaking and radiator issues are usually the main reason behind this overheating and hissing sound issue. However, a stuck thermostat is also a possible reason. Diagnose the vehicle and get these parts fixed to fix both the overheating and hissing sound problems.

The article discusses the issue of the car’s engine overheating and making hissing sounds. Read on to learn the causes in detail and their solutions.

Reasons Why Car Overheats Making Hissing Sound

While engine overheating is a serious car issue that requires checking immediately, hissing sounds demand fast attention. The hissing sounds are often reported to come from under the hood soon after the temperature warning light illuminates.

The following are the possible reasons the car overheats, making hissing sounds.

The coolant in the cooling system may be behind the hissing sounds when your car is overheating. The coolant runs through the cooling system to the engine, regulating its temperatures.

Engine overheating first means the coolant isn’t cooling the system as expected. Secondly, the hissing sound shows that the hot coolant or steam is leaking from a point in the cooling system.

The solutions include determining the leaking point, which can be a cracked hose or loose seal in the system. Since the engine and the cooling system are hot when the engine overheats, allow it time to cool before you diagnose the system. Also, you’ll need to drain the coolant from the system.

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Check for broken or loose hoses and replace them with new ones. If the leak is from a loose seal or gasket, install new seals.

Radiator issues are another possible reason behind this car overheating and making hissing sound issues. The radiator helps the coolant dissipate heat before returning to the engine and cooling it.

A radiator clogged with debris and dirt will not cool the coolant ideally, resulting in the engine overheating. A faulty radiator fan may also be behind the engine overheating.

Damage to the radiator, especially on the fins, will result in a hissing sound. The thermal expansion in the coolant causes pressure to increase when overheating

Car overheating and making hissing sound issues happens due to radiator clogged with debris

The solutions include determining the exact issue with the radiator and fixing it. The solutions include the following.

  • Cleaning the radiator

Use water (pressurized if possible) and gentle detergent to clean the detergent. You will also require the radiator brush to clean the fins to remove dirt and debris hindering it from cooling.

  • Replace The Radiator Fan

Another solution is to get the radiator fan replaced if the diagnosis shows that it doesn’t work, resulting in engine overheating. The steps to follow vary with the model. However, these are the most likely steps you will take to replace it.

  • Step 1: Get the replacement fan.
  • Step 2: Pop the hood and locate the fan on the radiator grill.
  • Step 3: Disconnect connectors surrounding the fan with power.
  • Step 4: Unscrew the fan from the housing.
  • Step 5: Remove the fan.
  • Step 6: Install the new fan.
  • Step 7: Screw it back on and reconnect the power connectors.
  • Step 8: Test the car.
  • Get The Radiator Fixed or Replaced
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A damaged radiator is fixed by sealing small cracks where the coolant is leaking from. However, replace the radiator to fix larger cracks. Radiator replacement is a labor-intensive repair job, so let the professionals handle it.

A stuck thermostat is another possible reason your car overheats and makes hissing sounds. The thermostat helps the engine warm faster by keeping some coolant circulating in the engine during startup. This prevents parasitic load from the engine and improves its performance.

However, when the thermostat is stuck closed, it won’t allow the coolant in the engine to flow to the radiator and dissipate heat. The result is the engine overheating. Also, you’ll hear a hissing sound since the expanding coolant creates pressure.

Stuck Thermostat

The solution is to clean or replace the thermostat to fix the issue of sticking closed. However, for either of these solutions, you must get the thermostat. Follow the steps below to access and remove the thermostat.

  • Step 1: Drain the coolant from the cooling system. To prevent antifreeze poisoning, wear protective gear.
  • Step 2: Disconnect the hose connected to the housing with the thermostat.
  • Step 3: Unscrew and remove the thermostat housing.
  • Step 4: Remove the thermostat.
  • Step 5: Clean the thermostat.
  • Step 6: Install the thermostat.
  • Step 7: Use a new gasket on the thermostat housing and screw it back on.
  • Step 8: Reconnect the coolant hose.
  • Step 9: Refill the cooling system with the manufacturer’s recommended coolant.
  • Step 10: Test the vehicle.

The video below shows how to change a thermostat on a Jeep Cherokee.

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Expect to pay between $200 and $350 if professionals do the replacement for you.

Most of the time, the issue causing a hissing sound will be behind the engine overheating. That means fixing the hissing you’ll also solve the engine overheating issue. However, in case the overheating issue persists, the following are the possible reasons.

  • Faulty water pump
  • Low coolant level
  • Air in the cooling system
  • Engine oil issues
  • Blocked exhaust system
  • Malfunction temperature sensor


If you still have questions about the car overheating and making hissing sounds, check the following FAQs for more clarifications.

Q1. What Should I Do When a Car Overheats Making Hissing Sounds?

When your car overheats and makes some hissing sounds, stop driving promptly. Call the roadside assistant to diagnose and fix the issue.

Q2. Is It Safe To Drive To The Repair Shop If the Engine Is Overheated and Has Hissing Sounds?

It’s unsafe to continue driving the vehicle under this circumstance. However, after allowing the engine time to cool, you can drive to a nearby repair shop and get the car diagnosed.

Final Thoughts

When your vehicle experiences this overheating and hissing sound issue, check the possible causes discussed above. Start by checking for a leak on the system and then the radiator, where cracks and leaks are a likely cause. If these components are okay, check the thermostat’s condition. It is necessary to take your vehicle to a repair shop to get it fully diagnosed and fixed. The professionals will have all the needed equipment to diagnose your car and provide the necessary solutions.

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