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Car Vacuum Leaks: Causes, Symptoms and How to Fix

When it comes to your vehicle’s engine, different parts can suffer all kinds of problems. One of the hardest things when it comes to troubleshooting your engine is finding out what the problem is.

Whenever unmetered air is starts leaking into your car, you can assume already that it’s a car vacuum leak. Yes, air leaking into your vehicle. This can mess up the air/fuel ration.

A vacuum leak can be tricky to spot. It’s an easy fix considering you’re only dealing with a vacuum hose and a few other parts. However, the smallest cuts in your vacuum hose can pose a challenge to a non-professional.

In turn, this then can affect a lot of processes that happen within your car’s engine. However, take note that car vacuum leaks can be caused by a lot of different factors.

What are Car Vacuum Leaks?

what are car vacuum leaks

Car vacuum leaks are quite hard to diagnose as these leaks can disguise themselves as something entirely different. Some usual symptoms of car vacuum leaks are hissing sounds and accelerator problems.

Accelerator problems are usually those times when you feel as if your vehicle’s idle speed is running faster than what is projected in your speedometer. Or when you’re having a hard time slowing down your car.

If you ever encounter just one of these, check your engine light immediately. This might help you diagnose what the problem is more easily

The Possible Causes?

We will be listing some of the usual and leading causes of car vacuum leaks. But remember, these might not be ALL of the reasons.

1. Wrecked Connectors

Plastic connectors stuck to the vacuum hose usually are the ones that usually break in time. This is because plastic is not that durable withstand the pressures of holding onto the vacuum hose.

This might be remedied by using metal connectors instead. Metal connectors are supposed to be more heavy-duty than plastic ones. So they might do a better job at not getting detached from the vacuum hose.

2. Loose and wobbly fittings

If your car doesn’t have any other issues, loose and wobbly fittings is usually the most frequent culprit for car vacuum leaks. Solving this one is pretty simple compared to the other possible causes of car vacuum leaks.

You can only just examine and check all your installations before tightening them again. However, buying more secure and perfect fitting facilities can help you avoid this particular problem.

3. Cracked vacuum hose

A cracked vacuum hose is usually caused by the friction on a vacuum hose whenever your engine is running. A vacuum hose tends to become brittle over time and might suffer abrasions. These abrasions come from withstanding the engine’s vibrations. Cracked vacuum hoses need to be either replaced or reconnected with a new vacuum line.

4. Torn throttle rod

Throttle sticks (or also known as throttle shafts) are large air regulators that control the airflow inside your car’s engine. Since vacuum leaks are just unmetered air leaking into your vehicle, torn throttle rods might also cause this. Keeping your throttle rods in check and properly maintaining them can help you avoid this.

5. Dysfunctional gasket

A faulty gasket can lose the ability to shut hard parts together and keep air out of your engine. This one you don’t have to replace right away, though. You can simply just repair a dysfunctional gasket to experience better performance from your vehicle.

6. Leaky exhaust gas recirculation valve

The EGR valve shaft accumulates carbon particles which make it unable to close properly/fully. This might also be a cause of vacuum leaks. To solve this, only clean the EGR valve shaft to get it working properly again.

7. Leakage in the power brake relay station

The power/brake relay station (also known as the booster) might wear out and cause leakages. No life hacks for this except to replace it with a new one.

So now that you know what the possible causes of vacuum leaks are, the next question is: what are its effects?

How Does A Vacuum Leak Affect Your Vehicle

The effects of vacuum leakages can be summed up to three: poor fuel efficiency, loss of power and engine damage. Poor fuel efficiency happens when your car engine is having difficulties maintaining a good air/fuel ratio. The leaking of unmetered air into your vehicle sets this air/fuel ratio off balance.

how does a vacuum leak affect

This can also damage your engine. Those loud hissing sounds you might be hearing might simply be from your car engine suffering damage from a vacuum leak. This kind of losses might range from weakening your engine’s combustion and fuel supply system to obstructing the delivery process itself of fuel to power up your engine.

Consequently, this damage in your engine might later cause a complete loss of power. It can be either your engine suddenly dying on you or finding yourself unable to start the engine the next day.

Things You’ll Need

Although fixing vacuum leaks is economical and easy, you’ll still need some tools to get the job done. Here is the list of materials that you’ll need:

  • Carburetor Cleaner – This filter will help you inspect for vacuum leakages by using it in various parts of the engine. Using a carburetor can change the speed of an idle engine if there are leakages.
  • Vacuum hose line – You’ll be only needing a replacement hose if the damage is severe. Later on, we will give instructions for small breakages that don’t require any overhaul.
  • Pliers – Used for cutting vacuum hose lines if necessary.
  • Gloves – For safety purposes!

How to Locate and Fix Car Vacuum Leaks

Vacuum leaks can be tough to find. Some are easy to spot, but others can be deep down your engine. Worse, these vacuum leaks can be as small as 0.02 inches. This makes it harder to find, but at the same time, the adverse effects remain the same. You can’t overlook it.

However, finding and fixing leaks can be quite easy even for the toughest of spots to find. Depending on how you execute it correctly, you can find it in your garage without any help of a professional.

Here’s a rundown of the steps you need to take to fix vacuum leaks.

#Step 1: Protection

The rule of thumb in fixing automobiles is safety first. That should be enforced even more when you’re handling the engine.


With that said, protect yourself first at all costs. You can wear goggles or laboratory glasses for added protection. Having thick working gloves is also good to avoid hurting your fingers. Also, be sure to remove any accessories near your hands or wrists such as watches and rings.

You wouldn’t want your fingers to get stuck inside the engine’s components because of these things. Likewise, distance yourself from the engine’s moving parts and don’t stick your hand where you can’t see it.

#Step 2: Inspection

As with any problem, you’ll need to find first where the point of origin is. Obviously, the first component that you’ll need to look at is the vacuum hose.

Before doing anything drastic, it’s best to get a vacuum hose diagram. You can search this up for your car’s model, but it also comes with your vehicle’s service manual. With this, you can check your vacuum hose systematically.

Check if each hose is connected to its right fitting. Do a hand check as well if it’s bendable or if the fitting is stable.


Afterward, check if there are any cracks present. Large cracks are easier to find but always remember, small cracks affect your car’s performance the same way. Consequently, it makes it harder to trace.

You need a thorough inspection at the vacuum hose. Just carefully look at the rubber. Moreover, inspect if there are any inconsistencies in texture by running your fingers across the hose.

#Step 3: Using Your Engine to Its Advantage

If visual inspection is not enough (this is normal if the damage is small), you can try listening to your vacuum hose. Usually, a hissing sound from a hose means it’s damaged. However, you can only do this while the engine is running. And trying to pick up a hissing sound from the hose is even more challenging while your engine is making its sound.

However, don’t be disheartened. You can still check the hose in a different way. For this step, we will utilize your engine to its advantage.


While the engine is running, let it idle and set the transmission to Park or Neutral. (If your car is an automatic, set it the former. If it’s neutral, the latter). After this, apply the emergency brake.

Next, get a carburetor cleaner. Spray the carburetor near the throttle bore gasket. By doing so, you’ll get a reaction from the engine if there is damage. The engine’s idle speed would start to increase as the cleaner is applied.

For further inspection, continue spraying the cleaner to the intake manifold plenum and base gaskets. Again, if there is something wrong, your engine’s speed will continue to increase.

#Step 4: Checking the Brake Booster

Next, we test the booster. Major vacuum leaks can happen in the brake booster because of the workload it suffers. Similar to the previous step, spray the cleaner around the brake booster. After this, observe the engine speed again.

A failed booster would also generate a hissing sound from the brake pedal.

brake booster

You should also check the vacuum booster for cracks and other damages since these are also susceptible to leakage.

#Step 5: Fixing the Leak

Now that you’ve located the leaks, whether it’s in the gasket, booster, or hose, it’s time to correct this problem finally.

To repair the vacuum leak, you must first label the hoses that are damaged. This only applies if you have multiple holes in different areas.The reason for this is because you might get confused in fixing the leaks if you don’t label it according to their fittings.

Attaching a piece of masking tape with a distinctive marking should be enough to label it.

fixing vacuum leak

Next, proceed to one hose at a time. If the damage is at the end of the hose, just only cut not more than an inch of it and reconnect the hose. That should solve it immediately.

On the other hand, if the cut or crack is in the middle of the hose, adding a small piece of vacuum line should do the trick. Be careful as this is tricky. If the hole is just small, cut it out and reconnect it using a union. If the damage is severe, total replacement might be the best option (Severe cuts are a rare occurrence, though).

Lastly, if you have a vacuum gauge pump, it’s best to utilize it. This checks the external system if there are other leakages.

This machine removes the vacuum tube from the engine to transfer it to the tester. Afterward, pump gauge and check if the system is working properly. You can refer to the guide or manual that comes with your gauge pump for additional instructions.

Summing It Up

Vacuum leaks are not as common as other engine problems that you might encounter. But if it does happen, then it’s inevitable for you to fix it.

The biggest problem with vacuum leaks is finding where the leak is. There are different methods as shown in this article that you can try. In fact, there’s more out there that you can further search on. What we indicated above are the easiest and most efficient ways to locate the leaks.

The good news is that once you’ve done that step, half of your work is already done. The fixing is quite simple, and most of the time you don’t need to replace the hose entirely.

However, it’s a whole different case if the damage is severe in the manifold, brake booster, or throttle rod. In these cases, repair and replacement might be the best option to take.

Just remember, locating and fixing vacuum leaks is easy if you do it in a systematic manner. Just be patient, and everything will go smooth and stress-free!

Steven K. Galloway