How to do a cylinder leak down test
A cylinder leakage test is performed on a car's engine to determine how a cylinder is functioning. The cylinder leakage test is also known as thecylinder leak down testor compression test. The leak down test can help the auto technician determine if the cylinder is weak or strong. What is a cylinder? The cylinder is a hole in the engine. A piston moves up and down in the cylinder to help the engine run. When the mechanic says this is a V6 engine; it simply means that the engine has six holes that distribute power in the engine.
You can perform a cylinder leak test by pumping air into the holes of the engine. However, there is a lot more that car owners, auto mechanics and car dealers need to know about theleak down test. These steps outline how to perform a cylinder leakage test on an automobile.
Get the right tools
In order to perform the leak down test properly, you must have the right tools. There are basically two types of cylinder leak testers. You can buy a single gauge tester or a double gauge tester from your local auto parts store. The gauges cost between $40 and $250. The single unit is used to check the cylinder pressure and then the input pressure. A double unit is used to measure the input pressure and the cylinder pressure continuously. You may have to make slight adjustments to make sure your readings are accurate.
Performing leak down test
First, make sure the engine is warm. Connect the leak down tester to the air source or the air pump. Keep in mind that you will be pumping air into the cylinder. Test only one cylinder at a time. Rotate the engine until thecylinder piston reaches the Top Dead Center(TDC) position. A balancer can help you reach TDC. Place the tester adapter in the spark plug hole.
Make sure yourcylinder tester reads zerobefore you start this procedure. Pump the air into the cylinder and write down your percentage reading from the tester and you are done. Now, you can perform the same procedures on the remaining cylinders.
What the numbers mean?
Air is forced into a cylinder at 100 pounds per square inch. Yourleak down tester readingis 80 pounds per square inch. This means that 20 percent of the air is leaking out of the cylinder. If you find a leakage of 15 percent to 20 percent, you need to find out where the leak is located.
Most leaks will occur at the intake valve, the exhaust valve or past the piston rings. No cylinder is going to seal at 100 percent. The best numbers are between 8 and 12 percent. A leak down test at 30 percent, or higher, indicates you have a serious engine problem. This test helps the car buyer, owner or auto technician determine the condition of the car's engine. Learning how to perform the cylinder leakage test can save you and your family thousands of dollars on auto repairs.
