Symptoms of a Faulty or Faulty Vacuum Pump

Common signs include poor fuel efficiency, difficult brake application, engine oil leaks, and a non-working air conditioner.

An internal combustion engine running on unleaded gasoline creates tremendous pressure inside a closed crankcase. This pressure is used to power several belts and pulleys, from alternators to AC units, but is released through the use of a vacuum pump. The diesel engine, on the other hand, uses vacuum pumps to provide power to other systems, primarily the braking system and, in many cases, the air conditioning system. The vacuum pump runs continuously as each cylinder inside the engine continues to work. When a vacuum pump fails or fails completely, it can significantly affect the overall performance and operation of the vehicle.

Since a vacuum pump is always used, the chance of some kind of mechanical failure or complete breakdown is more likely for diesel engines that use this component. The most common cause of vacuum pump failure is due to broken belts, electrical problems inside the unit, or failed vacuum hoses. On a car with a gasoline engine, the vacuum pump tends to act on emissions or the exhaust system; however, if not maintained properly, it can cause significant damage to cylinder head components.

The pump runs constantly if the motor is on, so wear and tear will eventually cause it to fail. When this happens, you will notice a decrease in braking performance. If your car uses a vacuum pump to operate the air conditioner, you will also notice that you cannot maintain a constant temperature in the cabin.

Here are some common symptoms that indicate a bad vacuum pump for gasoline and diesel engines.

1. Poor fuel economy

When there is a vacuum leak, it is most often caused by broken vacuum hoses, faulty connections, or a non-working vacuum pump. If you listen very carefully, you can sometimes hear a "hiss", which is a signal of a vacuum leak. However, it is most likely to be noticed when the engine is losing fuel efficiency. The reason for this is that the car's exhaust is delayed as it exits the combustion chamber. When burnt fuel accumulates, new fuel burns with less efficiency. This condition also reduces engine performance; but it really depends on the manufacture and use of the vacuum pump.

If you notice that you have poor fuel economy in both gasoline and diesel engines, have your local ASE certified mechanic have your vacuum pump, hoses, and engine checked for vacuum leaks.

2. The brake pedal is hard to press

This symptom is typical for diesel engines that use a vacuum pump booster to improve braking performance. This is especially true for larger diesel semi-trailers and rear wheel drive trucks with dual tyres. When the pump starts to fail, it produces less suction, which helps to pressurize the brake master cylinder and puts extra pressure inside the brake lines. In the end, the lack of pressure in the brake system takes its toll on the pedals. If there is a lot of pressure, the pedal will be firm but very gentle. When the vacuum pressure is low, the pedal is tight and very hard to push and apply the brakes.

When you recognize this warning sign, do not wait for this item to be repaired or inspected by professional mechanics. See a certified diesel engine mechanic as soon as possible.

3. Oil leak under the side of the engine

Most vacuum pumps are located on the left or right side of the engine, usually closer to the brake master cylinder on diesel vehicles. The vacuum pump requires oil to maintain proper lubrication and reduce internal temperatures due to its frequent use. If you notice oil dripping from the left or right side of the engine, it may be coming from the vacuum pump. Have a mechanic look into this problem no matter where you think the oil is leaking as it can lead to serious mechanical component failure if left uncorrected.

4. The air conditioner does not work

If your AC unit suddenly stops working, it could be caused by the vacuum pump, especially in diesel engines. If you notice a problem with your AC unit but it has recently been serviced, contact your local mechanic to have your vacuum pump checked for problems.

The above warning signs are just some of the potential symptoms of a failing or faulty vacuum pump. If you encounter any of these, be sure to contact AvtoTachki so that one of our local ASE certified mechanics can come to your home or office to inspect your vehicle, diagnose the exact problem, and offer an affordable solution.