How to pressure test an engine cooling system and why

You should pressure test the cooling system every time you open it up and reassemble it to make sure there are no leaks. After a cooling system flush, this is normally the following step. If a leak is detected, a pressure test can be performed.  In order words, pressure testing should be often done to avoid unnecessary breakdown of your car.

In this article, you’ll learn how to pressure test your engine cooling system and why you should pressure testing should be done. You’ll also know how much it costs to pressure test an engine cooling system and what causes no pressure in the system.

engine cooling system

Why should I pressure test my engine cooling system?

Pressure testing is done to check for leaks in the cooling system as well as the radiator cap. The hand pump with adapters to accommodate different size caps and the radiator filler neck is the most typical pressure tester.

Another sort of pressure tester connects to the coolant overflow hose with shop air. A third kind includes an adapter that replaces the radiator cap and allows a pressure or temperature probe to be inserted. To measure the pressure and check for leaks, utilize workshop air or simply the pressure generated by the coolant system.

Read more: Different types of refrigeration systems

How can I pressure test my engine cooling system?

For the cooling system, you utilize a pressure tester. Rent one from your local auto parts store if you don’t have one. Instructions will be included.

It usually attaches to the radiator near the radiator cap, and you manually pump it until the pressure on the gauge matches the pressure indicated on the top of the radiator cap. This pressure is usually between 13 and 16 psi in a modern automobile. Allow 20-30 minutes for the car to be under this strain. Then look for leaks throughout the cooling system and monitor the pressure gauge on the pressure tester for any changes in pressure. There is most certainly a leak if the pressure is lower than previously.

Make sure the radiator is full before using a hand pump tester to test the system. Connect the adaptor to the filler neck using the right adaptor. Connect the adaptor to the pressure tester. Slowly apply pressure to the system until it reaches the system’s range or the radiator cap’s range. For at least two minutes, the system should maintain pressure. If this is not the case, look for leaks in the system.

To use the hand pump to test the radiator cap, connect the cap to the pump with the appropriate adaptor and turn the pump on until the cap begins to release pressure. Take note of the pressure reading on the cap to ensure that it is releasing at the correct pressure. Stop putting more strain on yourself. For about one minute, the cap should be able to maintain this pressure. Replace the cap if it releases too early or too late, or if it does not hold pressure.

Install the adaptor with the pressure probe to test the system with shop air. Connect the shop air and raise the regulator setting to the system’s pressure rating. Turn off the shop air after the pressure has been attained. The system should be able to maintain pressure for at least two minutes. If the pressure drops, look for leaks in the system. If no external leaks are discovered, keep in mind that a broken head gasket could allow coolant to seep into the cylinders or the oil channels.

Read more: Understanding Automatic Lubrication system

Watch the video below to learn how you can pressure test your car cooling system:


What are the things I should know before pressure testing my car engine?

  • When the engine is heated, never open the cooling system. You will be burned by the coolant.
  • On newer automobiles, a cooling system cleanse should be performed every 100,000 miles or sooner if the coolant is unclean upon inspection.
  • A cooling system flush and/or repair of a leak in the cooling system may not be enough to solve an engine overheating problem. A specialist should examine this.


Will the coolant pressure test notice a blown head gasket?

The scientific test for a head gasket failure is to look for combustion fumes in the cooling system. If the compression has leaked into the cooling system, this test will reveal if the head gasket has blown.

How much does it cost to pressure test the head?

A reputable compression test performed by the technician will cost around $1000. The reason for this is that each injector must be removed and a new gasket installed. You must also apply the brake at this moment. For that, only 5-6 hundred dollars are required.

Read more: Understanding Radiator Pressure Cap

What is the pressure of a normal cooling system?

This pressure can range from 4 to 30 psi depending on the model (30 to 200 kPa). When the system pressure rises with the temperature, the pressure relief valve allows the excess pressure to escape.

What can cause the cooling system to have no pressure?

Leaky hoses are the most typical cause of radiator leaks, but you can also have leaks in the radiator itself, which can be a bigger issue. The pressure created by the coolant traveling from your radiator to your hot, running engine and back causes a lot of stress.

Read more: Understanding Automobile Radiators


With the explanation above am sure you now see why you should pressure test your engine cooling system and how you can perform the task. Pressure testing an engine cooling system can cost much but it is worth doing as it prevents some future damages. This testing process also helps to know if your car hoses are in good condition which is the issue of no pressure.

Join our Newsletter

I hope you learn a lot from this article, where how and why you should pressure test your engine cooling system are being discussed, if so, kindly share with other students. Thanks for reading, see you around!