How Does A Diesel Vacuum Pump Work?

A vacuum pump is a device that receives power from the engine cam shaft. It is driven by the alternator shaft in some designs. The vacuum pump’s primary duty is to remove air from the brake booster tank, creating vacuum that can be used for brake application.

How does the vacuum pump work?

A vacuum pump is a device that removes gas molecules or air particles from a confined space to create a pressure differential and a partial vacuum. Based on the pressure requirements and the application, vacuum pumps are designed in a number of technologies. Sizing a vacuum pump system to the proper settings is critical for achieving maximum efficiency.

A vacuum is a space that is devoid of matter and has a gaseous pressure that is lower than atmospheric pressure.

The main purpose of a vacuum pump is to modify the pressure in a contained region in order to create a full or partial vacuum via mechanical or chemical means. As gas molecules flow from high to low to fill the full area of that volume, pressure will always try to equalize across connected regions. If a new low-pressure region is provided, gas will flow naturally from the high-pressure area to the new low-pressure area until the pressures are equal. This vacuum is formed by pushing molecules rather than “sucking” gases. By switching between high and low pressure states, vacuum pumps essentially transport gas molecules from one region to the next, creating a vacuum.

As more molecules are evacuated from the vacuum space, it gets progressively more difficult to remove more, requiring more vacuum power. There are various groups of pressure ranges:

To help distinguish their capabilities, vacuum pumps are categorised by the pressure range they can achieve. These are the classifications:

  • High, very high, and ultra-high vacuum pressures are handled by secondary (high vacuum) pumps.

Vacuum pump technologies are classified as wet or dry depending on the pressure needs and operational use. Dry pumps contain no fluid in the gap between the revolving mechanisms or static pieces that are used to isolate and compress gas molecules, whereas wet pumps require oil or water for lubrication and sealing. Dry pumps require extremely tight tolerances to work successfully and without wear when they are not lubricated. Let’s take a look at some of the vacuum pump’s approaches.

Capture pumps, also known as entrapment pumps, are used for applications that need extremely high vacuum pressures and have no mechanical parts. Capture pumps can create a vacuum environment in two ways without utilizing moving elements.

Cryopump (Dry, Secondary): 7.5 x 10-10 Torr pressure, 1200 – 4200 I/s pumping speed

Using cryogenics to catch gas molecules is one of the strategies utilized by capture pumps to trap gas molecules. Cryopumps employ cryogenic technology to freeze or trap gas at an extremely low temperature. They successfully suck molecules inward to generate a vacuum by using extremely cold temperatures.

Sputter Ion Pumps (Dry, Secondary): 7.5 x 10-12 Torr pressure, 1,000 I/s pumping speed

As a method of entrapment, Sputter Ion pumps use extremely magnetic fields and ionization of gas molecules to make them electrically conductive.

A cloud of electropositive ions is created by the magnetic field and is deposited on a titanium cathode. Chemically active compounds mix with gas molecules to draw them in and create a vacuum in this process.

Kinetic energy or Positive Displacement are the two types of methods that transfer pumps can use. Transfer pumps, unlike Capture Pumps, drive gas molecules out of the space through the system. They all have one thing in common: they all use a mechanism of mechanically moving gas and air through the system at various intervals. Multiple transfer pumps are frequently used in conjunction to achieve larger vacuum and flow rates. Multiple transfer pumps are also commonly used in a system to provide redundancy in the case of a pump failure.

Kinetic pumps use the principle of momentum to push gas towards the outlet, either through impellers (blades) or by injecting vapor.

Turbomolecular Pump (Dry, Secondary): 7.5 x 10-11 Torr pressure, 10 – 50,000 I/s pumping speed

Because they are utilized for high pressure applications, all Kinetic pumps are secondary pumps. The Turbomolecular pump is a dry technology that propels gas molecules using high-speed spinning blades inside the chamber. The gas molecules’ rate of movement towards the outlet is increased by transferring momentum from the rotating blades to them. Low pressures and low transfer rates are provided by these pumps.

Vapor Diffusion Pump (Wet, Secondary): 7.5 x 10-11 Torr pressure, 10 – 50,000 I/s pumping speed

Vapor Diffusion Pumps employ high-velocity hot oil steam to draw gas molecules from the inlet to the outlet using kinetic energy. There are no moving parts, and the inlet pressure is minimized.

Positive Displacement is the other sort of Transfer. The essential principle of a Positive Displacement pump is that it moves small, isolated quantities of gas at successive stages by expanding the initial volume into the chamber, compressing to a smaller volume and expelling at a greater pressure to the outside. These pumps are classified as primary or booster pumps and use either wet or dry technology. They operate at lower pressures. The many types of positive displacement primary vacuum pumps are as follows:

Pressure 1 x 10-3 mbar, Pumping Speed 0.7–275 m3/h (0.4–162 ft3/min) Oil Sealed Rotary Vane Pump (Wet, Primary): Pressure 1 x 10-3 mbar, Pumping Speed 0.7–275 m3/h (0.4–162 ft3/min)

Sealed in Oil An eccentrically mounted rotor turns a set of vanes in a rotary vane pump, which compresses gases. These vanes glide out and produce chambers between themselves and the housing due to centrifugal force. Inside these chambers, the pumped medium is trapped. Their volume is constantly lowered as they rotate further. The pumped medium is compressed and transferred to the outlet in this manner. Single-stage and two-stage rotary vane vacuum pumps are available.

Pumping Speed 25 – 30,000 m3/h (15 – 17,700 ft3/min) Liquid Ring Pump (Wet, Primary): Pressure 30 mbar, Pumping Speed 25 – 30,000 m3/h (15 – 17,700 ft3/min)

Liquid ring pumps have an off-center impeller with vanes bent toward spinning that, due to centrifugal acceleration, generate a moving cylindrical ring of liquid around the casing. As the vanes rotate, they form crescent-shaped spaces of various widths, which are sealed by the liquid ring. The volume increases near the suction or intake, causing the pressure in each one to drop and draw in gas. Because of the eccentrically positioned impeller and the development of liquid rings, the volumes between each vane diminish as it turns. As the gas escapes, it is compressed, resulting in a continuous flow.

Diaphragm Pump (Dry, Primary): 5 x 10-8 mbar pressure, 0.6 – 10 m3/h (0.35 – 5.9 ft3/min) pumping speed

Diaphragm pumps are positive displacement vacuum pumps that use a dry way of operation. A diaphragm is mounted on a rod attached to the crankshaft, which turns the diaphragm vertically. When the diaphragm is lowered, the volume of the chamber expands, lowering pressure and drawing air molecules in. The volume decreases as the diaphragm rises, and gas molecules are squeezed as they flow to the outlet. To react to pressure fluctuations, both the inlet and output valves are spring loaded.

Scroll Pump (Dry, Primary): 1 x 10-2 mbar pressure, 5.0 – 46 m3/h (3.0 – 27 ft3/min) pumping speed

Scroll pumps employ a spiral design with two non-rotating scrolls, the inner of which orbits and traps a gas in the outer volume space. As it orbits, the volume of gas gets smaller and smaller, compressing it until it reaches the minimum volume and maximum pressure allowed, at which point it is expelled out the spiral’s center outlet.

Roots Style Pumps (Dry, Booster): -3 Torr Pressure, 100,000 m3/h (58,860ft3/min) Pumping Speed

As the counter rotates, root pumps push gas in one direction via two lobes that mesh without touching. As the volume increases at the intake while decreasing at the output, this counter rotation creates maximum flow rate, compressing the pressure. These pumps are made for applications that demand the removal of significant amounts of gas.

Pumping Speed 100 – 800 m3/h (59 – 472 ft3/min) Claw Pumps (Dry, Booster): Pressure 1 x 10-3 mbar, Pumping Speed 100 – 800 m3/h (59 – 472 ft3/min)

Claw pumps contain two rotary claws that rotate in opposite directions. They are commonly utilized in tough industrial situations because they are exceedingly efficient, reliable, and minimal maintenance. The Claws are only 2/1000″ apart, although they never truly touch. The internal seal is optimized by the limited space between the Claws and the chamber housing, which eliminates wear and the need for lubricants or oils.

Screw Pumps (Dry, Booster): 1 x 10-2 Torr pressure, 750 m3/h (440 ft3/min) pumping speed

Screw pumps use two revolving screws, one left-handed and one right-handed, horizontally positioned along the inside of a chamber and meshing without contact. Gas molecules are caught between the two screws at one end, and when they turn in opposing directions, the gas is propelled into space with a smaller volume, compressing it as it approaches the outlet and lowering the pressure at the intake.

What happens when vacuum pump fails?

The enclosed crankcase of an internal combustion engine running on unleaded gasoline generates up a tremendous amount of pressure. This pressure is utilized to power a variety of belts and pulleys, from alternators to air conditioners, but it is released via a vacuum pump. A diesel engine, on the other hand, uses vacuum pumps to power various systems, including the brake system and, in some cases, the air conditioning system. As each cylinder in the engine continues to fire, the vacuum pump runs continually. When a vacuum pump malfunctions or fails completely, it can have a substantial impact on a vehicle’s overall performance and functioning.

On diesel engines that use this component, the likelihood of experiencing some sort of mechanical failure or complete breakage is higher because the vacuum pump is always in use. Broken belts, electrical difficulties inside the device, or faulty vacuum hoses are the most typical causes of vacuum pump failure. The vacuum pump affects the emissions or exhaust system on a gasoline-powered vehicle; nevertheless, if not properly maintained, it can cause considerable damage to cylinder head components.

If the engine is running, the pump is continually running, and wear and tear will eventually cause it to fail. You’ll notice a drop in braking performance if this happens. If your vehicle’s air conditioning is controlled by a vacuum pump, you’ll discover that it’s difficult to keep a consistent temperature in the cabin.

For gasoline and diesel applications, below are some frequent indications that indicate a faulty vacuum pump.

How do I know if my vacuum pump has a vacuum leak?

This entails submerging a punctured bicycle tube and identifying the source of the bubbles, or pouring washing up liquid around the joint of an active water/gas pipe to see where the bubbles/froth originate.

A closed vacuum vessel is evacuated until a specified pressure is reached in this test. The pump’s inlet valve is then closed and then reopened after some time. If the time it takes to return the vacuum to its initial level remains constant after multiple repetitions, there is a leak. If this time decreases, gas is most likely being removed from the interior of the system — but a leak is still possible.

The pressure decay test is effectively the inverse of this test. It entails recording the vacuum level and the time it took to reach that level. If a leak exists after isolating the system, the curve will become a straight line.

It’s also a good idea to keep an eye on the pressure after the pump has been turned off and the pressure has been reduced to a specific level. There could be a leak if pressure continues to grow. Strong degassing from liquids or vessel walls raises pressure as well, thus it’s not a foolproof indicator of a breach.

A helium leak detector is the sole technique to detect a leak smaller than 1×10-6 mbar *l/s (which may, for example, be viruses leaking into the system).

Helium is commonly employed not just for its capacity to detect small vacuum leaks, but also because it is light (low mass), fully inert/non-reactive (and so safe), and relatively inexpensive.

How does a 2 stage vacuum pump work?

Dual stage pumps combine a low vacuum stage and a mated high vacuum stage into one unit. The high vacuum stage collects process gas and sends it to a second, lower vacuum stage, which compresses the gas to atmospheric pressure, enhancing the pump’s vacuum performance.

Why water is used in vacuum pump?

Water is generally utilized to seal the vacuum chamber within the pump housing when utilizing a liquid ring vacuum pump. A special sealing liquid, which may be a byproduct of the industrial process itself, may be utilized in some cases when the vacuum is drying materials saturated with other chemicals. Light oils for liquid rings are frequently used as practical and cost-effective options. Allow the specialists at Premier Fluid Systems to assist you in finding the ideal solution for your needs.

How do you test a vacuum pump?

Close the valve between the system and the vacuum pump/micron gauge setup and start the vacuum pump before opening the vacuum pump and micron gauge to the system. Only the vacuum hose and micron gauge will be able to pull a vacuum.

In a reasonable amount of time, the micron gauge should register a 500-micron level. If it doesn’t, the micron gauge, vacuum pump, or interconnecting hose are malfunctioning. Before connecting the vacuum pump to the system, you must figure out which of these devices is causing the issue and fix it.

Can oil leak from vacuum pump?

Thank you for taking the time to look at our website. Hopefully, the information provided here is both fascinating and useful. We would much appreciate your support if you find this information beneficial. We provide this, as well as a variety of other useful DIYs, to the VW and Audi community. The only thing we ask in return is for your assistance when it comes time to make a transaction. With your help, we can continue to devote resources to creating pages like this one.

A common source of oil leakage is the 2.5 L mechanical vacuum pump.

If this describes you, read on for additional information on how to remedy the leak on your 2.5 engine.

#07K145100H Pierburg 2.5 Vacuum Pump for VW (Same Manufacturer as the OEM just no VW logo)

If you have an oil leak originating from the driver’s side of the engine, your Volkswagen 2.5 Mechanical Vacuum Pump is most likely to blame.

The outside of this portion has a cover that frequently leaks.

An arrow points to the point where the cover and vacuum pump housing meet in the image below.

If your 2.5 was leaking, you’d notice oil around the bottom of the cover where it connects to the housing.

Unfortunately, VW does not provide a seal between the vacuum pump cover and the pump itself (or anyone else as far as we know).

The Vacuum Pump as a whole must be replaced.

Please note that this 2.5 Vac Pump has been modified with a new outer cover that appears to be made of a different material from the prior version. Both of the aforementioned versions are the most recent revisions at this time.

A faulty vacuum pump will frequently leak oil, resulting in a pool of oil beneath your 2.5’s engine and transmission.

The leak will be more noticeable where the engine and transmission connect, and it is frequently mistaken as a faulty rear main seal.

The simplest way to tell whether you have a leaky vacuum pump is to look for oil buildup on top of the vehicle’s transmission.

When trying to locate an oil leak, it’s often easier to start by cleaning everything and then running it to determine where the leak is coming from.

This is an excellent DIY project for manual gearbox autos because it is a pretty simple installation.

On automatic transmission 2.5 engines, the transmission should be removed according to the manufacturer’s instructions, however there is a non-book option that can save you a lot of money by not having to remove the trans.

Take a look at the video below to see how to install this 2.5 vacuum pump on a VW 2.5 with an automatic transmission without removing the transmission.

On a VW 2.5 engine with an automatic transmission, how to repair the vacuum pump

To learn more about how this 2.5 vacuum pump fails, watch this video.

What causes poor engine vacuum?

A lower-than-normal vacuum reading at idle could suggest leaking from the intake manifold gaskets, manifold to carburetor gaskets, vacuum brake booster, or vacuum modulator. Low readings can also be produced by worn piston rings or very late valve timing.

How does a vacuum diaphragm fuel pump work?

A composite membrane flexes up and down over a fuel bowl in diaphragm pumps. The bowl contains two inputs and outputs, each with a check valve to guarantee fluid flow is only one way. As the diaphragm rises, a vacuum is created, drawing fuel from the fuel tank into the fuel bowl. The actuating lever then lowers the membrane, forcing the fuel out at a pressure of around 6 psi for carbureted engines. Mechanical diaphragm pumps are almost solely used in older carbureted engines, and some of the less expensive aftermarket electric pumps are also of this type. Diaphragm pumps are simple in design and function, and they last a long time. A diaphragm pump will normally work again after 20 years if it is given a fresh supply of fuel.