How to Find Vacuum Leaks and Faults
Not only is a vacuum leak one of the most common problems in vehicles, it is also one of the most annoying because the leak is difficult to find. Even the best technicians can face difficulties at some point in their careers.
Luckily, there are a number of tricks used by repair shops across the country to find a vacuum leak as soon as one or more signs of a vacuum leak are detected. Here is a step-by-step guide to finding a pesky vacuum leak.
How to Find a Vacuum Leak (Step-by-Step)
The following steps can be used to identify and isolate one or more vacuum leaks in a given engine. However, it is imperative that you follow each step listed below completely and complete it in the order specified.
1) Become Familiar with Your Vacuum System
Your vehicle’s vacuum system is made up of multiple components and complex hoses. Before you begin the diagnostic process, it is best to become familiar with your vehicle’s vacuum system and its paths.
Many vehicles have an engine compartment diagram of the entire vacuum system that you can use as a reference. If your vehicle does not have this type of diagram, you can find one in the appropriate model-specific service manual.
2) Check for vacuum leaks
Because vacuum leaks are often mistakenly considered the cause of various secondary problems, it is important to confirm the presence of such a problem before beginning the diagnostic process. To do this, connect a vacuum tester to the vehicle’s vacuum system.
This tester can be operated to create a vacuum without running the vehicle’s engine. If any leaks occur, this vacuum will escape and be quickly eliminated.
3) Perform a visual inspection
Carefully inspect the vehicle’s vacuum system, visually tracing each hose and component. Look for signs of dislodged or damaged hoses or components that appear to be damaged.
A relatively clean engine may also show signs of unevenness or soot around or near the damaged engine intake seal or throttle valve seal.
4) Listen for Unusual Noises
Next, start your car’s engine and listen for any unusual hissing, squealing, or whistling noises. Such noises usually indicate a vacuum leak and are caused by air being sucked in through small cracks in the hoses or seals in the vacuum system.
5) Use a Propane Torch
If your visual and hearing tests fail to identify the source of your vehicle’s vacuum leak, try using a simple propane torch to identify the source of the leak. A propane torch is an easy way to find vacuum leaks. First, start your car’s engine and open the valve on a portable propane burner, but do not light the burner while it’s in use.
Next, move the unlit propane torch in small increments throughout the engine’s vacuum system. You will notice a visible change in engine speed as it passes the leak.
6) Use a Carburetor Cleaner
Alternatively, you can use a carburetor cleaner just like propane when identifying the source of a vacuum leak in your engine. Slowly work your way through the engine’s vacuum system while carefully spraying the carburetor cleaner. As with propane, spraying the carburetor cleaner at the source of the vacuum leak will cause a noticeable change in RPM. This is a direct result of the carburetor cleaner being consumed during combustion.
7) Use a Fog Machine
This requires specialized products, but a fog test can help you identify the problematic vacuum leak. This is usually accomplished with an automotive smoke machine like the AutoLine Pro, which is installed directly into the vehicle’s intake tract.
This type of fog machine, once set up, will work and send smoke throughout the vehicle’s intake tract. In most cases, smoke will rise from the area where there may be a vacuum leak.
How to Repair a Vacuum Leak
The method required to repair a particular vacuum leak will vary greatly depending on the cause of the leak itself. Simply put, not all leaks are the same, and the cost of repairing a vacuum leak can vary greatly. Some are due to the engine’s delicate network of vacuum hoses, while others are due to damaged intake gaskets. Using our example, each type of leak will require an entirely different repair methodology.
Generally, however, the vast majority of vacuum leaks can be repaired by simply replacing a damaged vacuum hose or heat-tested intake tube. This type of repair is very simple and should only take a few minutes. In fact, the vast majority of vacuum leaks take much longer to diagnose than they do to repair. On the other end of the repair spectrum are old or damaged seals in the intake tract. These primarily include the intake manifold gasket and throttle valve gasket on your engine.
Leaks in either location will cause roughly the same problem and require seal replacement. This type of repair is usually much longer as it requires disassembly and reassembly.
In addition, the repair process to repair a damaged intake or throttle body gasket will vary from vehicle to vehicle. In all cases, consult the manufacturer’s specific service literature for each vehicle before performing any repairs.