How to find a Vacuum Leak & How to Fix It (8 Easy Steps)

A vacuum leak can result in many different symptoms in your car engine. Here's how you can test and ensure there are no vacuum leaks in your car engine

How To Find A Vacuum Leak

A vacuum leak can cause many different problems with your car engine and even more if you do not fix it as soon as possible.

But how can you locate the vacuum leak, and are there any methods you can use without buying all fancy tools?

There are actually several methods you can use to find a vacuum leak. Some more reliable than others, so let’s begin!

How to find a Vacuum Leak

The easiest way to find a vacuum leak at home without using any tools is to carefully spray a flammable liquid around the areas where you suspect the leak may be coming from when the engine is idling. If the engine RPMs increase, it’s a vacuum leak there.

This method can be dangerous if you are not careful, as you can cause your car to catch fire! We always recommend using the right tools to find vacuum leaks! Do it at your own risk, and always do it outdoors. Keep a fire extinguisher nearby. (Note: Never spray near hot parts or ignition parts.) These steps should only be done by professionals!

Go further down in the article to find more safe methods.

Total Time: 5 minutes

1. Visually Inspect Vacuum Hoses

Cracked Vacuum Hose

The first step you should take before you go further into this guide is to check all the vacuum hoses for cracks or completely broken hoses. Vacuum hoses are made of rubber material, which will become hard and start to crack after some years in the engine’s heat. Replace any faulty vacuum hoses you can find.

2. Start the Engine

Hard Starting

If you couldn’t find any cracked or leaky vacuum hoses or other parts in the engine bay, it is now time to fire up the engine. Apply the parking brake, put the gearbox in Neutral or Park, and fire up the engine. Be careful not to touch any moving or hot parts during this guide!

3. Get a Flammable Spray Ready

Flammable Spray

To continue this guide, you need a flammable fluid in spray or gas form. You can use starter spray, brake cleaner, carburetor cleaner, or propane gas from a propane torch, for example. We do strongly recommend using a carburetor cleaner or propane torch for these steps.

4. Carefully Spray Around Intake Manifold Gasket

Spray Manifold Gasket

Take the spray and try to locate where the intake manifold is connected to the cylinder head, and carefully spray around the connection here on each cylinder. If the car’s RPM changes or starts to sound weird, your car most likely has a bad intake manifold gasket. You can also try to spray around other suspected areas on the intake manifold if it’s divided into several parts.

5. Carefully Spray Around Vacuum Hoses

Spray Around Vacuum Hoses

Locate where all the vacuum hoses are connected on the intake manifold and spray around the connections of them. Even if they look good, there can be small cracks in them that are leaking. You can also follow the hoses and spray the other end of them. If the engine RPM gets higher or lower, you have definitely found a vacuum leak.

6. Carefully Spray Around Brake Booster Hose

Brake Booster Hose

The brake booster builds a vacuum with a one-way valve to make sure you do not have to press super hard on the brake pedal to brake. Spray around the connection to it and other areas around the brake booster to try locating any leaks. You have to be very carefully listening to the engine’s RPM here, though, because t is so far away from the engine, so it is not sure that it will be noticeable.

7. Carefully Spray Around Solenoids & Actuators

Intake Axles

Look around the intake manifold and follow the vacuum hoses to find solenoids and actuators connected to the vacuum system. These solenoids and actuators are often made of plastic, which can crack with time. Spray around these, especially if they have axles attached to the intake manifold like in the picture above. Replace faulty actuators or solenoids if you find a leaky one.

8. Carefully Spray Around Throttle Body

Car Intake Throttle Body

Now we have one last step to check, and it is the gasket between the throttle body and the intake manifold. Your throttle body is bolted with 3 or 4 screws into the intake manifold, or there is often a rubber or paper gasket between these two parts. It happens that this gasket goes bad and starts to leak. Spray around other areas around the throttle body also to check for leaks.

Estimated Cost: 5 USD

Other Methods to find Vacuum Leaks

Spray Intake Manifold

So if you think the guide above is a little bit too risky with flammable fluids, you can also use other methods. Here are three different ways you can use to find vacuum leaks!

RELATED: 6 Symptoms of a Vacuum Leak & Causes

1. Visual and Listening Checks

In some cases, it is straightforward to locate vacuum leaks just by looking at the components in the engine bay. Check for any cracked or broken vacuum hoses or other signs that there is a leak. Often around a leak, it can be a little bit of oil also, so look for signs of oils around the intake.

Vacuum leaks often cause high pitch sound on idle also, and you can usually locate the leak by just listening with your ears. Be careful not to touch any moving or hot parts while listening, though.

2. Soap & Water

You can also use soap and water to find leaks around the intake. However, this method is more effective when the air is pushed out – and not sucked in like a vacuum leak. With the soap’s help, you should be able to see where the leak is coming from. To be honest, I haven’t tried this method very much, and it is up to you if you want to do it.

3. Use an EVAP smoke machine

Car Smoke Machine Test

This is the method for professionals that want to find vacuum leaks super fast in a very safe way. The downside is that you need an EVAP smoke machine, which can often cost over 1000$, and it is probably nothing you have in your garage.

However, if you have the luck to borrow one from a repair workshop, you should definitely do it. If you own a workshop and do not have a smoke machine, it is strongly recommended. You will save a lot of time in troubleshooting.

Find a Vacuum Leak FAQ

What can I spray to check for vacuum leaks?

You can spray anything flammable fluids, but be careful with any materials that can damage the engine. We recommend only use carb cleaner, brake cleaner, propane gas, or starter spray.

Can you use Carb Cleaner to find a vacuum leak?

Yes, carburetor cleaner works really well for this job, and it is actually one of our recommended fluids to use to find vacuum leaks.

Can you use starting fluid to find a vacuum leak?

Yes, you can use starter fluid to find a vacuum leak. However, in our opinion, it is a little bit too flammable for this job and is a little bit dangerous. Brake cleaner or carb cleaner works better.

Can you use brake cleaner to find a vacuum leak?

Yes, using a brake cleaner works very well for the job of finding a vacuum leak. It depends slightly on different brake cleaner brands, but make sure that the brake cleaner is not too much or too little flammable.

Magnus Sellén
Written by:

Magnus is the owner and main author of Mechanicbase. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.

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