Internal combustion engines require a mixture of air and fuel to operate.
The compressed mixture ignites, pressing the pistons that rotate the crankshaft, and the car moves. The air reaches the engine via a small throttle valve. A vacuum is created to control the auxiliary units.
A vacuum leak causes unwanted air to enter the engine in places where it is not needed. This reduces the performance of the engine and leads to malfunctions in some systems that rely on the vacuum.
Since the vacuum leak causes engine inefficiency, you will notice that the engine light on the dashboard comes on.
You will also have problems accelerating; this is because the combustion chambers are not effectively supplied with fuel. The vacuum is used in some vehicles to operate actuators, sensors or power brakes.
If a vacuum leak occurs, some of the sensors may malfunction and force you to make unnecessary repairs.
To identify a vacuum leak, you must first understand how the engine air intake works. Air enters through the air filter and the throttle controls it while creating a vacuum. You know your car has a vacuum leak if it makes a hissing sound when you start it.
Vacuum hoses begin to wear out after miles of use; they become brittle, and this causes breaks in certain areas. Inspect your engine hoses carefully and replace them when they are no longer of any use. Engines are different, and you must first refer to your car’s engine manual. This should contain a diagram of how to adjust the engine.
Different ways to check for vacuum leaks
There are several ways to check for vacuum leakage. Some are faster and some require expensive equipment. Check out all these steps to find the best solution for you.
1. Visual inspection and testing for loose engine hoses
The first place to check for a vacuum leak is the hoses connected to the motor. Check them for cracks or loose fastenings. Every car has a unique engine hose. Make sure that the hose clamps that hold the hose in place are strong enough.
You can do this by moving the clamps sideways; if they move easily, tighten them. If you still cannot identify the leaking areas, investigate the surfaces further.
2. Spray soapy water around the intake area
This is probably the easiest and cheapest way to check for vacuum leaks. By spraying soapy water around the inlet and affected hoses while the engine is running, you will see air bubbles flowing out if there are leaks in the affected area.
3. Use an EVAP smoke machine
This is the professional way to do it and the way mechanics check for vacuum leaks within minutes. But you need expensive equipment. If you are interested in investing in a great machine for finding vacuum leaks, you can take a look at our guide here: Best EVAP Smoke Machine.
4. Spray carburetor cleaner or starter fluid
There are those who use carburetor cleaners to detect vacuum leaks. In this procedure, you put the car in neutral and spray part of the cleaner on places where you suspect a vacuum leak. The engine will start running faster if there is a vacuum leak.
This is because the carburetor cleaner gets into the engine and burns with fuel. However, this is a dangerous method of checking for vacuum leaks because the liquid is highly flammable.
Leakages in the intake manifold
If your hoses are okay, the problem could be with the intake manifold. The intake manifold gasket sometimes leaks, causing vacuum leakage. This should be located between the cylinder head and the manifold.
Spray the area with some soap to clean it and to detect any leaks. Set your car to park or idle to check for leaks in the intake manifold. Make sure that the wheels are immobile. Start the engine and let it idle for a few minutes.
Use soapy water spray in the area between the intake manifold and the cylinder head and at the base of the carburettor. Listen for the noise coming from the engine – if it smoothens during spraying, the vacuum leak is at the intake manifold and must be repaired.
What are the symptoms of a vacuum leak?
The first symptom of a vacuum leak is that your engine light comes on. There are many reasons why the light comes on, and you must rule out other causes before you conclude that it is a vacuum leak. But you can be sure it is a vacuum leak if it is accompanied by hissing engine noise and loss of power.
If your car doesn’t peak even after accelerating, it could be a vacuum leak. A vacuum leak can cause other engine problems such as inefficient fuel consumption.
Engine Hose repair tip
If you suffer from a damaged vacuum hose, you do not need to buy a new one if the damage is not so severe. The vacuum hose is long and you can cut off the damaged part and reconnect it to the engine.
The most sensitive damage is to the ends of the hose. You can use a sharp kitchen knife to cut off the ends. Always make sure that the hose clamps are tightened firmly to prevent further leaks. There are some vacuum leaks that occur when the hose is exposed to hot engine surfaces.
You must redirect the hose from the hose. After repair, start your engine and let it idle. Pay attention to possible hissing noises. If you decide to replace a vacuum hose, replace it with a similar hose of the same length and diameter. Vacuum hoses are intended for specific locations such as brake boosters or PCVs.
A vacuum leak can cause your vehicle to accelerate slowly. It can also interfere with the efficient fuel-air mixture in the combustion chambers. Damaged hoses are the main cause of vacuum leaks.
You can repair small hose leaks by cutting off the damaged parts when they are at the ends. If this does not work, you will be forced to buy new hoses.
Hello I’m Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I’m specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I’m here to give you answers to all your automotive questions and I hope that you enjoy our content.