Leak Down Test

How To Do A Leak Down Test?

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Car tests come in various types, and these tests are used to evaluate your car’s working efficiency. One of the most common and most straightforward of them all is the leak down test.  All it takes to get on with the test are some elementary equipment, time, and technical know-how.

A leak down test is a measuring of the functions in the internal combustion engines. To be more specific, it’s a measuring instrument to determine the rate at which the compressed air in the cylinder leaks out. It is why we’ve compiled this article. We’ll be diving into everything you need to know about the leak-down test. This is otherwise called a cylinder leak down test.

What is a Leak Down Test?

A leak down test involves adding air pressure gauges into every engine cylinder. A leak down test component is infused with a two-dial display. This two-dial display is what makes the leak down test unique from other tests.

One of the gauges is specifically meant to measure the incoming air pressure that enters the cylinder through the compressor. The other dial takes note of any form of air leakage that occurs in the cylinder.

The leak-down test is all about testing the engine’s capability to withhold pressure. The test will be able to tell you what is potentially responsible for a loss in compression. This should not be taken as the compression test. There’s a little difference between the two modes of tests and we’ll talk about it shortly. But suffice to say that a leak-down test is a reverse of a compression test.

Typically, loss in compression can be caused by a range of factors, including leaking or blown head gasket, stuck open intake valve, burnt or bent exhaust valve, or broken piston rings. Other components around the cylinder that may warrant the leak down test also include the cylinder wall and head (to check if they’re cracked),  

The greatest benefit of carrying out the leak-down test is that you can know the overall condition of the engine by testing the low cylinder or all the cylinders.

Guide to Perform Leak Down Test Results

Interpreting leak-down test data is relatively easy; however, before you can learn that, you’ll have to understand how to perform the test. It is why we will be looking at guidelines to Perform the leak down test results. The first thing to consider before your set out on your leak-down test is to get the tools required. The following tools will be needed:

  • Spark plug socket and socket wrench
  • Air compressor
  • A leak down test component

Once you have these tools in place, the next thing is to start to perform the test. How will you start? Let’s begin.

You can start by taking out all the spark plugs from every cylinder, using your spark plug socket and socket wrench. For a better result, you locate the top dead center in all of the cylinders then connect the air compressor.

For this to be done, the spark plugs need to be removed. Once you are done with the sparkplug removals, get a long thing object and out inside the spark plug hole. If you can get a hold of a screwdriver, it will be the most ideal.

Making use of a wrench, turn the engine with the crankshaft. Once the screwdriver is positioned in a way that it neither rises nor falls at every turn of the crankshaft, then you’ll know you have reached the top dead center of the cylinder.

Take out the screwdriver from the spark plug hole and replace it with the leak down test component. Activate the parking brakes of your car and leave it in gear. If your parking brakes don’t stop your vehicle from rolling, you can use a block to wedge your back wheels just in case.

Once the leak down test component is connected to the cylinder; you’ll need to connect the air compressor to the leak-down test component. After the connection, the regulator should be turned in a clockwise direction for the influx of air.

How to Read Leak Down Test Results?

This leak down test results will come in two pieces of information. The first result will be displayed on the right dial of the leak down test component. It will contain a set of percentages ranging from 0 to 100 percent. No 0 reading is possible, and 100 percent reading is not impossible, depending on your engine’s quality.

Rating System

  • A pressure loss of 1 to 10 percent means your engine is still in a good condition
  • A pressure loss of 10 to 20 percent calls for concern. Your engine might still be up and running, but the efficiency will be dropping.
  • A pressure loss of 30 percent and above is a huge cause for alarm and calls for an urgent solution.

Leak Down Test vs Compression Test

Using either of these tests will give you the best results needed to understand what is happening to your engine. They may have similarities because they are involved in the activities going on in your engine’s combustion chamber.

Despite these similarities, they still work differently. Compressor tests are used to measure the volume of pressure that an engine can produce. In contrast, a leak-down test involves adding air pressure into all the cylinders and, at the same time utilizing the gauges to monitor the pressure levels and leakages.

In sum, while a compression test looks to determine your car engine’s capacity to generate pressure, a leak-down test performs a more expansive function by inserting a compression scale into the cylinders that make up the car engine.

Final Thoughts

It is a brief rundown of all you need to know to do a leak-down test because we know there might come a time when one will be necessary for your vehicle. We hope that this article has given you the essential knowledge of what a leak down test involves.

There are tons of leak down testers out there. But you need to use the best tool so you can get a perfect reading that will guide your determination of the section of the engine where the actual problem resides.

Source & Feature Image: Mobil

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