How Does an Oil Pump Work?

Engine oil circulates through the engine to lubricate moving components, create a barrier between metal parts, seal the combustion chamber, wash sludge buildup off of internal parts, and keep the engine running cool. To move the oil around, every engine is equipped with an oil pump. It’s unusual to think about it much – if at all – unless your oil pressure light is on and symptoms start to show up.

Because there are huge differences in engine design and oil flow requirements, there’s a vast range in oil pump prices. Yours could be as low as $10 or more than $350, and an average price is between $100 and $150. How does an oil pump work and what should you know about diagnosing and repairing it?

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What is an Oil Pump?

The oil pump pressurizes the oil and sends it through the engine to lubricate and cool the moving parts such as the crankshaft, pistons, and bearings. This helps reduce friction and wear on these components, which prolongs the life of the engine. In fact, an engine that doesn’t have a working oil pump will likely overheat and seize in a few minutes or less, causing irreversible damage to internal components.

An oil pickup tube draws oil up out of the oil pan sump and pushes it through oil galleys to the oil filter. Then, the oil carries on through thinner channels or galleys that feed lubricant to bearings, moving parts, and a stream that coats upper end components. It all drains back down to the oil pan where it’s collected and goes through the process again. The oil pickup tube where it all starts is connected to the oil pump.

How Does it Work?

There are two main types of engine oil pumps: gear pumps and vane pumps.

Gear pumps use two gears that mesh together to create suction and pump the oil. The gears rotate, trapping oil between them and then pushing it through the pump’s outlet. These pumps are typically used in older, mechanical engines.

Vane pumps use a rotor with sliding vanes to pump the oil. As the rotor spins, the vanes create suction that pulls oil into the pump. The vanes then move outward, compressing and pushing the oil through the pump’s outlet. Vane pumps are typically used in newer, electronic engines and are often integrated into a front engine cover.

Both types of pumps are driven by the engine, whether by the crankshaft or camshaft, and can be either internal or external to the oil pan.

What to Look Out for in Servicing Your Oil Pump

Identifying a bad oil pump is the first step. There are several signs that an engine oil pump may be failing:

  • Low oil pressure. One of the most common signs of a failing oil pump is low oil pressure. This can be indicated by the oil pressure gauge or warning light on the dashboard, or by using a pressure tester during diagnosis.
  • Noise from the engine. A failing oil pump can make a whining or ticking noise, especially when the engine is idling. It could be from hydraulic lifters that are oil-starved or bearings or pistons that are no longer protected by a film of oil.
  • Overheating engine. A lack of oil pressure can cause the engine to overheat, as it is not being properly cooled.
  • Poor performance. A failing oil pump can cause the engine to lose power, stall, or not start at all. It’s often due to an oil-fed component like a turbocharger that stops working when it doesn’t get enough oil.
  • Oil warning light. Some vehicles have a warning light that comes on to indicate low oil pressure, which may be caused by a failing oil pump.
  • Oil leaks. If there is an oil leak from front of the engine, it may be a sign of a problem with the pump.

It’s important to note that some of these signs can also be caused by other issues such as low oil level, clogged oil filter, or worn bearings, so it’s crucial to diagnose the problem correctly to avoid further damage.

What Causes a Bad Oil Pump?

Oil pumps are a sturdy design and, if your engine is properly maintained, it should last your car’s entire lifetime. The primary point of failure for an oil pump is if oil changes aren’t performed on time. Sludge and other contaminants or debris can get lodged in the pump or pickup tube, causing the pump’s gears or vanes to wear prematurely.

Operating your engine at high RPMs for extended periods can also contribute to early failure. As the oil heats up too much, it permanently loses its viscosity and the oil pump can experience wear, whether inside the pump or on the drive gear.

It’s a big job to replace the oil pump on most vehicles. Along with draining the oil, the oil pan and front engine cover often need to be removed. But it’s easy to help prevent failure in the first place by changing the engine oil regularly, and avoid over-revving your engine for long stretches.

If you need an oil pump, shop at AutoZone. You’ll find high-quality parts from top brands in the industry, and Trustworthy Advice from AutoZone associates. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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