What Are Vacuum Lines And What Is Their Function? (Vacuum Lines Explained!)

Last Updated on January 14, 2023 by Leepu Da Maxim

In particular, vacuum lines are flexible rubber connections. These vacuum hoses or vacuum tubes direct the vacuum from the manifold to various fittings or components. The vacuum can be used to power various parts of the engine such as a wiper motor or a vacuum servo brake. Also, a car can contain about 12 vacuum lines. 

Key Takeaways

  • In vehicles, vacuum lines are small plastic pipes and their main purpose is to carry engine vacuum to various components in the vehicle
  • Vacuum lines are very important equipment for a vehicle because it allows the engine to perform various tasks like operating the brake booster, controlling the HVAC system, etc.
  • If there is any problem with the vacuum lines then the car won’t perform properly because the engine will heat up very quickly
  • If there is any hissing or sucking noises coming from your engine then this is an indication that your vacuum lines are damaged

Tips For Understanding Vacuum Lines

Common Vacuum Controlled DevicesMost Common Problems and Repairs
Exhaust Gas Re-circulatory Valve ( EGR )Vacuum leaks are the biggest problem in the vacuum system of any engine.
Some vacuum leaks are easy to detect while others are very difficult
The tools that allow for finding a vacuum leak are:
Starter fluid can vacuum pump vacuum diaphragm 

Brake Booster
Exhaust By-pass Valves ( Like Those Found On Ferrari)
Pop Up Headlights
Cruise Control
CrankCase/ Valve Cover Vent
Heating / A/C Vent Controls

How Do I Know If My Engine Has A Vacuum Leak?

As many people may know, car engines are mostly large air pumps. In particular, a mixture of fuel and air is required. Once the vehicle engine introduces air this mixture is compressed to produce combustion. This procedure is necessary and is what allows a vehicle to generate speed.

Additionally, the accelerator of a vehicle is one of the main components that are responsible for introducing air into the engine. In particular, drivers do not usually drive a vehicle with the throttle completely open all the way. Therefore, in these cases, the air must be extracted from the engine. For this purpose, a butterfly valve is used where the air is extracted.

This component is usually partially closed to create a vacuum in the intake manifold. In this case, the vacuum is used by the vehicle to control and feed a certain amount of secondary devices. Besides, the engine vacuum is often used for other functions. One of the best-known is the reduction of the effort required when pressing the brake pedal.

Other emission control systems also depend on this negative pressure. This can prevent these emissions from escaping and exhaust fumes from the crankcase. In the past, the windscreen wipers were operated with an engine vacuum. This is why a classic muscle car used to have a maximum of three vacuum lines.

1. One vacuum line for the automatic transmission modulator

2. A vacuum line for the brake servo

3. A vacuum line for the vacuum advance in the distributor

The vehicles of the late 1960s began to include at least a dozen girls and vacuum connections. This happened mainly as emission controls became more common. So, any one of these vacuum lines or connections was a possible location for a vacuum leak. 

So, one of those hose or fitting joints may start leaking. Here, the problem could be from an engine check light, a sudden drop in fuel economy, or erratic idling. Even some vacuum leaks can be easier to detect than others.

Common Concepts Of Vacuum Leakage

In principle, it is necessary to take into account that the performance of the motor can decrease even if it is a small leak of 0.0 20 inches. Also, the engine check light is understood and the driving ability is compromised by this small vacuum leak. At the same time, it is necessary to consider where the device that measures the incoming air is located.

This is necessary, as vacuum leaks often occur below the mass airflow sensor. In other words, more air is coming into the engine than is being measured. The computer inside the car is getting a false reading with levels that are too low. Of course, more air means an improper air/fuel mixture.

Typically, the ratio of air to gasoline in an average car is 14.7:1. Besides, computer measurements begin to vary inappropriately when there is a vacuum leak in an engine component.

Even when an exhaust-mounted oxygen sensor is included the excess air will be quickly detected by the computer. In this sense, the computer needs to compensate for the excess air with a larger amount of fuel. This is how the vehicle’s closed-loop self-correcting system works.

This may be one of the explanations of why fuel efficiency is becoming much more negative than before. Of course, increased fuel response starts to create a lot of additional problems for the various engine components. You even have to consider that engine intake is necessary for most modern cars.

This system is mostly used for a variety of controls on different aspects of the car. This is why it is necessary to apply the necessary repairs as soon as possible when a vacuum leak is detected. Also, it is necessary to request the help of a professional mechanic to avoid producing greater errors in these inconveniences. 

Use Carbohydrate Cleaner

One of the most efficient and simple methods to detect a vacuum leak is to use a carbohydrate cleaner. In principle, it is necessary to prevent the engine computer from continuing to enrich the mixture with more fuel. This requires a person to pull any sensor such as the throttle position sensor cable. 

So, this can keep the engine in open-loop mode. This is where any computer allows you to use pre-set values that are already coded to determine the precise amount of fuel. Even this prevents the computer from automatically adjusting the mixture to stay close to the 14.7:1 ratio.

In general, most internal combustion engines tend to have this same air-to-fuel ratio. You should then start the engine and simply let it idle. At the area of the leak, you should spray the carbohydrate cleaner spray. Of course, there must be no source of ignition in the engine.

This is an important and somewhat dangerous step as it could result in exaggerated combustion. Besides, an overheated exhaust manifold or a stray spark can be more than enough to cause a fire and large burns. So, the user must be careful not to get burned in the procedure.

In this case, the vacuum leak will suck out the combustible carburetor cleaner. Also, the engine will have the ability to return to idle speed momentarily. Even the operation will be from all cylinders if one has failed. To be able to locate the leak, you should use short direct breaths of the carburetor cleaner. 

There is also another way and it is based on using an extinguished propane torch to find the exact location of the vacuum leak. Here, the off-propane torch is used in the same way you would be using the carbs cleaner. A piece of hose is needed to rummage around in the engine compartment.

This component is usually placed over the valve outlet of the torch. In this case, the propane fuel should be vacuumed up by the engine that is running too poorly. From there, the engine should be smoothed out and accelerated slightly.

Finally, it is also possible to use some less-flammable elements to reduce the danger. So, here you can spray engine oil or water on the vacuum leak to be able to locate the exact point of the problem. The engine at idle changes and the flow of additional oxygen is interrupted when the water is sucked in by the vacuum leak. 

What Is A Vacuum Hose Made Of?

In general, rubber is used to manufacture vacuum lines. There are also options for different qualities depending on the manufacturer. That is why you can also find vacuum hoses made specifically with silicone. In any case, vacuum lines must be replaced since they are a set of components that have a certain life span.

In particular, manufacturers of silicone vacuum lines mention that these options offer a longer service life. In this case, a material is used that is much more durable and resistant than rubber to various detrimental factors. Along with this, less frequent maintenance is also required, although possibly a higher budget is required. 

What Are The Symptoms Of A Vacuum Leak?

One of the main signs that indicate a vacuum leak is the engine speed. In this case, the engine rpm can be exaggerated. This happens specifically because more air is circulating to the engine. 

On the other hand, the engine can have a hesitant operation when it is idling and stopped. Besides, the engine may be sucked in or have a loud squeal or whistle. Of course, there are other symptoms although these are the most common and are included along with a decrease in fuel efficiency.

What Happens If You Drive With A Vacuum Leak?

Generally, the driver may notice a loss of engine power due to an improper air-fuel mixture. Of course, this affects driving ability and can be dangerous.

Even driving with a vacuum leak can aggravate the problem. The car also consumes a greater amount of fuel to compensate for the increased amount of air entering the engine. In any case, it is recommended to replace the vacuum lines and apply the necessary repairs as soon as possible.