How to Perform a Leak Down Test

There’s a honestly huge selection of tests you could perform to judge your cars functionality. It’s sort of great that perhaps one of the most useful can be among the easiest to execute. We’re discussing Leak Down Testing.

All you have to to perform among they are some quite rudimentary tools, just a little understanding and some time for you to spare on the sunny afternoon. In this specific article we’re going for a deep dive take a look at Drip Down Exams. What they are, what they perform – and how exactly to perform one.

Is certainly a Drip Down Test a Compression Test?

First factors first and we must deal with a common misunderstanding right here – a Drip Down Test isn’t a Compression Check. They are very similar, therefore we realize why they could be confused with one another. But they are different varieties of tests.

Using a compression check, a pressure gauge is normally linked to the engine instead of the spark plugs. When the engine is normally cranked, the measure can measure this pressure. That is a compression check. It is an excellent indicator from the engines capability to generate pressure, which is required to crank and convert the engine cylinder.

Poor pressure equals a vulnerable cylinder that used will convert as an underperforming engine that wheezes rather than roaring.

Exactly what is a Drip Down Test?

If that is clearly a compression test, after that exactly what is a Drip Down Test? Well, hold on within and we’ll let you know just what it is. Prepared?

A Drip Down Test is normally a Compression Check backwards.

Even as we specified above a compression check is focused on calculating the pressure which the engine can generate itself. A drip down test also contains placing a pressure measure into each cylinder in the engine – though in this situation it really is a Drip Down Test device that is put, with a display that incorporates two independent dials or displays.

Leak Down

It is this dual dial display that really makes the Leak Down Test both different from the Compression test, but also helps make it so useful. One gauge measures the air pressure that is being introduced into the cylinder from the compressor. The second dial then tells you the percentage of the air that is leaking from your cylinder (if any!)

You can see then that having a compression test, you are measuring the engine’s ability to generate pressure. Having a Leak Down Test you are measuring the power for the engine to carry that pressure in. Both lab tests are therefore essential methods to measure engine health insurance and performance – and they’re also very different.

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How exactly to Perform a Drip Down Test?

So we’ve taken a look at why you should perform a Leak Down Test. In the section after this, we’ll look at how to use and interpret the data the test will generate. But before you can get to that stage, you need to know how to actually perform a Leak Down Test.

The first thing you are going to need is to gather your products! You are going to need:

  • A Leak Down Test Tool
  • An Air flow Compressor
  • A Outlet Wrench using a Spark Plug Outlet

The very first thing you will have to do is normally to eliminate the spark plugs from each cylinder together with your outlet wrench and spark plug outlet.

For the Drip Down check to work correctly, then you initial need find the very best Dead Center for every cylinder before starting up the environment compressor. To get this done then you should take away the spark plugs as above. When they are eliminated, insert something long and thin into the spark plug opening – a screwdriver will do the job. Change the engine by hand by using a wrench within the crankshaft. When the screwdriver is at the stage where it is no longer rising or falling with each change of the crankshaft, the cylinder is at Top Dead Center.

Remove the screwdriver and connect the Drip Down Test device in to the spark plug gap. Place the automobile into gear when you can, but also employ the car parking brake so that it won’t move. Chocks behind the tires may also be useful.

When the Drip Down Test device is mounted on the cylinder, another task is to add the device itself towards the surroundings compressor. After the compressor line is connected, convert the regulator clockwise to permit the environment to flow in to the cylinder.

The proper hand dial gives a reading as a share. This means that the pressure reduction that is happening (i.e. the quantity of atmosphere escaping the cylinder). But even more on that ina moment!

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How exactly to Read the Outcomes of a Drip Down Check – Component 1

A drip down test will provide you with two – yes TWO – models of data. The first is pretty simple to interpret, whilst the additional will demand you to be something of the motor vehicle detective.

The first group of outcomes is there in your hands, displayed for the right-hand dial for the Drip Down Test device. The dial will become organized with percentages, generally which range from 0% to 100%.

To begin with, do no anticipate a 0% reading! You can find precious few motors with the construction and strength to withhold 100% of air pressure. We hate to break it to you but you are not going to find that kind of engine in your minivan.

Instead, check out this rating system:

  • 1 to 10% Loss – All is good. This the typical range of pressure loss that you will find in a normal, happy engine.
  • 10% to 20% – Pressure loss in this range is a red flag. Your engine will still be working fine at this range, but you are going to start to notice a loss of performance. As the pressure loss moves up toward 20% that performance loss will get more pronounced. If any of your cylinders are testing in this range, it isn’t cause for instant concern, but perform add engine fixes to your upcoming to accomplish list.
  • 30% or even more – If you’re viewing engine pressure reduction assessed at 30% or even more than your engine is certainly in trouble! If you’re seeing readings within this range after that incomparable some exploratory function to discover – and fix – the issue.

Don’t forget that all cylinder works separately. So whilst it might be a discomfort in the butt, you choose to do need to have a look at each one and perform a complete Leak Down Check on each cylinder.

How exactly to Read the Outcomes of a Drip Down Check – Component 2

As we said, a Leak Down Test will give you two sets of data. The readings around the tool are a very useful indicator of engine health. But a leak Down Test can also help you to pinpoint where the problems actually are inside your engine.

Assuming of course you actually do have any problems that is usually. In the event that you the dial reading is certainly under 6 or 7%, we’d suggest you don’t even bother checking out this section, unless you are interested in fine-tuning your engine. If however your pressure leak readings are worryingly high – 10% or over – then you need to bust out another key set of tools in your mechanics armory.

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Yep, the other set of data that you can get from a Leak Down Test comes from listening to where the pressure is usually leaking. So for example, check out:

If you hear air flow coming out of the air intake, out of your carburetor or out the throttle body then that suggests your problem is with the air intake valve itself.

Leak Down
  • Exhaust Valve

The issue could of course be down the other end of the car. If you can hear air flow escaping in the exhaust manifold, in the turbocharger or in the tailpipe itself in that case your problem is probable a leaky exhaust valve.

If the environment is certainly escaping through the dipstick pipe or the essential oil filler cap, the problem is likely a put on piston band.

  • Damaged Cylinder Mind

No-one really wants to hear they possess a damaged cylinder mind. But if you’re running your Drip Down Ensure that you you see that your coolant is certainly bubbling up from the radiator throat, then a Cracked Cylinder Head could well be your problem.

That, by the way, is the reason why we like the Leak Down Test so much. Not only will it help give you an idea of the health of your engine, but it also helps to diagnose what the problem is with your engine too.

That’s fairly cool if you think about it.


There you have it folks, our comprehensive instruction to the drip down check. We’ve informed you what it really is, we’ve informed you how exactly to get it done and we’ve informed you how exactly to interpret the outcomes that you will get. Heck, we’ve also told you why it really is such a good test to execute.

We wish you could see why it really is therefore useful as well, and we actually hope that you’ll execute a Leak Down Test on your own car.

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