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Low Oil Pressure: Meaning, Causes, Symptoms, and Fix Guide

Here's where you can find out all about low oil pressure
In this article, you’ll learn all about low oil pressure

Various reasons can cause a sudden drop in your engine’s oil pressure. Also, driving a car running low on oil pressure can cause major and expensive damages and should always be avoided. It’s therefore important to be vigilant at all times. To help you with that, here are the major symptoms of low engine oil pressure, the most common causes and what you can do to fix it.

How The Engine Oil System Works

Low oil pressure
Low Oil Pressure Warning Light

A car engine is made of moving metal parts, rubbing against each other at high speed. To prevent wear and tear of contact surfaces, a film of pressurized oil provides lubrication to the engine components. This pressure is generated by an oil pump driven by the engine. In addition to the lubrication function, the oil circuit allows:

  • The engine to cool down through a heat exchange with the hottest parts;
  • Protection of the metal parts of the engine from corrosion;
  • Cleaning the engine of foreign bodies (metal particles, gaskets and joints residues, etc.).

Since the oil pressure varies from 14 psi on average to 75 psi at high speed, it is necessary to constantly monitor the minimum pressure value and make sure it stays constantly within the threshold. If this minimum value is not reached, a pressure sensor, also known as a “pressure switch” or “oil pressure sensor”, electrically supplies the low oil pressure warning light to the instrument cluster.

When there is a drop in oil pressure, an insufficient oil amount may not reach the top of the engine and no longer fulfill its role of lubricating correctly, causing the seizure of different components.

Oil pressure drops can be caused by several phenomena but in every case, will cause extreme wear of the engine in a very short time. That’s why it is said that when the low oil pressure light appears on your dashboard, it is often already too late.

How To Test Oil Pressure?

To ensure the good engine operatioin, oil pressure testing is  indispensable
How to test oil pressure ?

To check the engine oil pressure, a tool is used to measure the hydraulic pressure inside the system while the engine is running. Professional oil pressure gauges come in a kit including:

  • A pressure gauge usually ranging from 0 to 140 psi;
  • A flexible hose with a fitting;
  • Various adapters for different car brands and models.

To measure the oil pressure in the system, connect the pressure gauge instead of the oil pressure sensor,  usually located on the oil filter adapter or the engine block. Start the engine, let the engine warm-up for at least 15 min or until it reaches its normal operating temperature. Keep the engine running over 2000 rpm and note down the pressure on the gauge. If it’s not within the normal values, more troubleshooting will be needed.

How to test the oil pressure

What Should Engine Oil Pressure Be?

In a normal situation, the pressure should be around 40 psi when the engine is running at 1000 rpm, and around 60 psi when it runs at 4000 rpm. Note that the recommended pressure can vary greatly from one vehicle to another. Some cars come equipped with a dry-sump lubrication system operating at a higher pressure rather than standard oil systems. Before prematurely jumping to conclusions, it is highly recommended to check the oil specifications by looking in your vehicle’s repair manual.

What Does Low Oil Pressure Mean?

A low-pressure condition happens when the oil pressure fails to reach the minimum recommended value at startup or when the value stays below the normal operating pressure threshold for an extended period. A low-pressure state is not to be mixed up with an incorrect oil level which will, in turn, cause the same symptoms and consequences. 

Low Oil Pressure Symptoms

Low-pressure Oil Light On

The engine oil pressure warning light is a vital safety component for your vehicle. It is designed to let you know whenever the pressure reaches a dangerously low level to prevent any damage to your engine. It was also one of the first control lights installed in automobiles.

A red oil burette icon is often used by manufacturers to represent the oil pressure warning light but some newer cars will simply indicate “low oil pressure” in the information display on the dashboard. No matter what icon is used, if it comes on, it means the situation is critical. It is better to stop the engine as soon and as safely possible.

Indeed, at this stage, the oil is no longer able to properly lubricate the various metal components inside the engine. Ignoring this warning sign can lead to premature deterioration of important parts or even a serious breakdown.

Blinking Oil Level Light

In some cases, the oil level indicator may start blinking instead of being constantly lit. The first thing to suspect in this situation is either a slightly low oil level or poor electrical contact.

When the level is only slightly lower than the minimum required to trigger the warning light, it is common to see the blinking following the bumps on the road or when turning the steering wheel.

Moreover, poor electrical contact to the sensor connector or exposed wire coming into contact with the body of the car may also cause the oil pressure dial to malfunction or the indicator to blink by mistake.

Noisy Engine

When the oil pressure is insufficient, the lack of lubrication causes more friction between the internal parts of the engine. It’s nott uncommon to hear a greater friction noise than usual. Hydraulic lifters can also start to produce a distinctive rattle noise.

Most Common Low Oil Pressure Causes

In general, a drop in the engine oil pressure is due to the malfunction of one or more elements. It can be caused by a problem with the pressure sensor. Failure of this device often leads to engine oil leakage leading to even bigger problems.

Insufficient oil pressure can also cause irreversible damage to the oil pump, which must be under constant pressure to function properly. An oil pump that runs dry for an extended period will probably never work as well as it used to and will often need to be replaced.

The use of an incorrect engine oil type or grade, a leaky oil filter, an improper oil level, a leaking engine oil cooler or a clogged strainer can all also cause a low oil pressure condition on your vehicle. But before going any further, let’s see all of these causes in more details.

Faulty Oil Pressure Sensor

Whenever the low oil pressure warning light comes on, the first thing to check is to make sure that the sensor itself is in good working order. If the sensor is defective, it will start sending inaccurate readings to the PCM which may cause the warning light to turn on for no apparent reason.

On certain newer car models, the proper operation of the oil pressure sensor is essential to ensure proper lubrication of the engine’s components considering that the PCM uses its data to adjust the oil pressure in real-time.

Faulty Oil Pump

The oil pump job is to build up the pressure and to circulate the oil into the system to make sure all the engine components are correctly lubricated. The pump draws the oil contained in the oil pan and propels it into the engine block and the cylinder head.

When the pump starts to age, air bubbles can form inside the housing while it operates, which will have the direct effect of reducing the oil pressure, which will in turn light up the low-pressure warning light.

On older vehicles, the oil pump was usually operated by the timing chain which greatly reduced the risk of failure but caused an additional load on the engine,  reducing the fuel efficiency. To remedy this situation, newer car models are now equipped with electric oil pumps effectively reducing the load on the engine but leaving room for potential electrical problems.

Incorrect Engine Oil Grade

When it comes to the oil grade to use in your engine, it’s super important to respect the manufacturers recommendation for the viscosity and oil type. Every engine is different and optimized to work best with a particular oil grade.

However, the oil may undergo premature aging. If the piston rings allow combustion residues to get into the oil pan, the fuel’s chemical components can break up the chemicals and greatly reduce its lubricating properties.

In the case where the instrument panel oil indicator does not go out as it should after start-up, immediately check not only the oil level but also its color and viscosity. If the oil is black and runs slowly down the dipstick, an oil change may be required.

Faulty Oil Filter

The oil filter is one of the most important components of the lubrication system of an internal combustion engine. It filters dirty oil, removes dust particles and retains metal flakes contained in the oil.

An oil filter clogged with debris can stop filtering the oil properly, allowing the particles to flow right back into the engine, gradually damaging the internal components.

Furthermore, a completely obstructed oil filter will substantially limit the oil flow which will considerably reduce the efficiency of the lubrication system . Filter replacement will be required immediately.

Defective Engine Oil Cooler

When driving under load or when hauling a heavy trailer, the engine’s temperature can quickly rise and get out of hand. On such vehicles, an external oil cooler is used to allow the engine cooling system to evacuate the heat contained in the oil.

The engine oil is transferred to the coolers using an adapter located between the engine block and the oil filter. The oil flows through the cooler while the coolant is circulating around it, absorbing the excess heat in the process.

If the vehicle is serviced as needed, the cooler should last as long as the vehicle. However, there are occasions when the oil cooler may become clogged and limit the passage of oil.

The oil filter adapter can also be the cause of the problem in some cases. Internal O-rings can sometimes leak and cause a significant drop in pressure.

Finding the exact source of the leak is easier if you start by cleaning the outside of the engine with a degreaser foaming spray. Protect electrical parts with plastic bags or plastic sheets and spray the degreaser around the area. Wait for a little and wash it out with water. Start the vehicle and let it run for a few minutes. Inspect around the adapter and replace the O-ring if needed.

Engine Oil Leak

Any other leaks in the lubrication system can also create a drop in pressure. The most common causes are, among others, the seals of the timing case and the front or rear seal of the crankshaft. In both cases, the leak will be greater when the engine is running. Be careful, though. The rear crankshaft oil seal is usually hidden by the transmission so the only visible sign of leakage is often a drop from the bottom of the transmission housing.

Even a small leak can end up causing worrying problems if the source is not corrected quickly. Over time, the oil level may slowly fall below the required minimum level and cause air bubbles in the system that can induce significant engine damage.

In any case, the only remedy for a seal leaking oil is to replace it without any delay. Be sure to check that the seal has not been damaged by another moving part to avoid facing the same problem again in a couple of weeks. Make sure that rotating parts with which it’s in contact are smooth and free of defects before replacing the faulty seal.

Low Oil Level

Driving with a low engine oil level can create important and expensive damages as well as increasing the risk of ending up with a seized engine. Seizure pretty much means the death of your engine as there’s not much to be done at this point. The engine will need to be opened up and inspected but, in most cases, the head will be warped and the piston will have scratched the inside of the cylinders to a point of no return. A complete overhaul could still save the engine but the total cost may be quite high and often beyond the residual value of the vehicle.

Clogged Oil Strainer

On older vehicles, oil pans can rust and metal shavings can float inside the oil pan. To prevent these debris from entering the oil system, manufacturers install a strainer on the opening of the tube connected to the oil pump.

Normally, regular oil changes should prevent the accumulation of large debris inside the oil pan but sometimes, it’s simply not enough. Dust or sand may have been able to enter the valve cover and is causing the camshaft to scratch against the head, producing small metal flakes or maybe carbon deposits found on the inside of the combustion chamber fell into the oil pan. Whatever the case is, debris found in the pan could clog the strainer, reducing the oil pressure in the system.

When something like that happens, remove the oil pan and remove the debris and metal shavings using a vacuum cleaner. Do not use a blowgun or you risk pushing small metal fragments into the oil pump. Unclogging an oil pump is a lot more complicated than simply removing an oil pan and often requires the front cover and timing belt/chain to be removed.

How Serious Is The Problem?

Low oil pressure problems are not to be overlooked. The oil in your engine is the same thing as the blood in your body. If it’s dirty or contaminated, if the pressure is not high enough or your arteries are clogged, you won’t live for long and it’s the same with your engine. The oil system is one of the most vital in your vehicle and should be treated accordingly. Neglecting the regular maintenance of the lubrication system will have a direct negative impact on the lifespan of your car and its resale value.  

The Bottom

No matter the original cause, drivers should react promptly at the first symptoms of low oil pressure. Most of the times, replacing the defective component will solve the problem right away. When in doubt, it’s always best to contact a certified automotive technician or to bring your car to the nearest auto repair shop. Keep in mind that ignoring the symptoms of an illness does not make it disappear, on the contrary, it often makes things worse. The same goes for your vehicle. Regular maintenance and a mechanic you can trust will always be your best asset for keeping your car healthy and reliable for as long as possible.

Read more: How To Test A Car Battery With A Multimeter

Jean-Claude Landry

Jee is a professional auto mechanic by day and the editor of TheMechanicDoctor.com by night, a website oriented towards beginner and professional auto mechanics offering free resources as well as tips, tricks, tutorials and all kinds of other helpful stuff for car enthusiasts.

Web: https://obdadvisor.comEmail: [email protected]
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