When a car has a vacuum leak it means that air is leaking into the engine from places that should be sealed. These leaks reduce the overall efficiency of the engine and disrupt the functionality of various systems that rely on a well-sealed vacuum system. If you suspect that your car has a vacuum leak, you should know where to look for the problem so that you find obvious faults. But if you can't find the leak instantly, you can use new methods to find it or, failing that, seek professional help.
Part 1 of 3: Do a Preliminary Inspection
Step 1. Check the engine vacuum diagram
To help you understand where the vacuum hoses are located and the likely areas where there is a leak, review the diagram that details how the vacuum system works. This diagram is usually found in the repair manual that has been made for your specific make, model and year of car.
You can find a large number of repair manuals in virtual stores or download them from the internet in digital formats
Step 2. Start the car and try to hear a whistle
When your car has a vacuum leak it usually manifests itself by causing a hiss at first. You may hear it from inside the car, but you are more likely to hear it when you open the hood with the engine running.
Try to pinpoint where the hiss is coming from. This will help you figure out where the leak is specifically
Step 3. Check for any loose or broken hoses
If you suspect you have a vacuum problem, checking the engine for apparent problems is a good idea. Look for hoses that are loose at one end or that are worn or clearly cracked. If you encounter a problem like these, this is most likely the cause of the engine failures.
- The number of hoses that the engine has and their locations vary greatly according to each engine specifically.
- Use a flashlight while looking at the engine so that you can see as many areas as possible.
- Small cracks in a hose can cause a leak. A visual inspection may not be enough to find these types of leaks.
Step 4. Turn off the engine and make sure the hose clamps are tight
Vacuum leaks almost always occur at the connection point between the hose and the solid part of the engine. Make sure the clamps that hold the hoses to the engine are tight. You can do this by gently moving the hose and clamp; the latter should not move at all when you pull it or when you pull the hose.
- Make sure the engine is off and cool to the touch when you do so.
- If any clamps move, you need to tighten them again. Most clamps have a screw that tightens the ring when you turn it.
- Even if you can't find a damaged or loose hose, you could still have a vacuum leak. You will just have to search its origin more deeply.
Part 2 of 3: Detect Leaks
Step 1. Spray soapy water over the areas you suspect are leaking
If you suspect that you have a vacuum leak in a specific area, you can spray soapy water from a bottle and spray bottle to see if there are any problems. Spray it on the suspicious area while the engine is running. If the car's idle levels off after applying the soapy water, it means the leak has probably been temporarily blocked.
You may need to spray multiple times and in different places to find the exact location of the leak
Step 2. Place a pressure gauge on the suspected hose
To find a leak, you can test the hoses individually to see if they hold up to pressure. Purchase a pressure gauge at your nearest auto parts store and attach it to the hose in question. Start the car and let it idle for a few minutes. When the engine is warm you will have an accurate reading on the pressure gauge.
Under normal conditions you can have between 43, 2 and 50, 8 cm (between 17 and 20 inches) of vacuum. If the hose is less than this, it must have a leak
Step 3. Consider going to the mechanic for help
If you haven't been able to find the vacuum leak yourself, it's a good time to go to the mechanic. Describe the problems you have seen with the engine and allow him to diagnose the problem.
In some cases the mechanic will have a machine that uses smoke to find the leak. This will surround the area where it suspects the problem with smoke and look for the points where the smoke begins to be sucked into the engine
Step 4. Spray starting fluid or carburetor cleaner in the areas where you suspect a leak
Traditional mechanics have used starting fluid or carb cleaner for years to find leaks. Simply let the car idle and then spray a small amount of cleaner or starter fluid over the place you suspect a leak. If there is, the engine will speed up for a moment. This happens because the fluid or cleaner was sucked up and added to the fuel that is burning in the engine.
This is a relatively dangerous method of finding vacuum leaks. It is risky to spray combustible material on the engine while it is running. It will generally work fine and will not burn out of the engine; but if there is any spark or some point is overheated, it can cause fire in the engine or even an explosion
Part 3 of 3: Identify the Symptoms of a Vacuum Leak
Step 1. See if the engine light on the panel comes on
Due to the decrease in engine efficiency caused by a vacuum leak, the engine light on the panel may come on. A vacuum leak is not the only cause of the check engine light on the panel, but it is one of the most common.
If the check engine light on the panel comes on, you should take the car to the mechanic. The mechanic will be able to connect a digital scanner to the car that communicates with the car's computer. This will specifically show why the light is on
Step 2. See if the car's acceleration efficiency has decreased
When the engine has a vacuum leak it takes more work to move the fuel. If you're stepping on the gas as hard as you always have and the car still isn't accelerating as it should, it's because you have a vacuum leak.
Step 3. Pay attention to the idling of the car
If there is a vacuum leak in the system, the car should show greater acceleration than normal. You will probably see that the engine sounds different than usual and revs with higher RPM when not in motion. This is caused by excess air being sucked into the system.
A very high idle can be a symptom of other problems as well, such as a problem with the computer or with the accelerator
Step 4. You should be suspicious of vacuum leaks if the car stops unexpectedly
When leaks are extreme, the car can stop running and can damage the engine. This is because the car is not able to draw enough fuel into the engine to keep it running.