Most people already know the simple truth that oil is the lifeblood of most vehicle engines. The only exception nowadays is electric vehicles, which rely on electrical energy from their battery packs. The traditional internal combustion engine, however, relies entirely on engine oil to function properly.
OEMs build in several key features and components that help us keep one eye on the level and condition of oil within our vehicle. First, there’s the dipstick, which is the quickest and easiest way to have a look at the car’s current oil level, as well as its condition. But how can we have a good idea on the status of our oil when we are driving? After all, we can’t keep stopping to check the dipstick every few miles.
Two more critical components are the oil level sensor and the oil pressure sensor, both of which form the main focus of today’s blog post. Let’s start with some background on why the level and condition of your oil is so important.
Background: Importance of Oil Levels and Condition
As we mentioned above, oil is the lifeblood of the engine and simply can’t function without it. The oil both cools and lubricates the many, many moving parts within the engine as it works. If you were to take the oil away, the engine would still physically start and work as normal at first, but it wouldn’t take long for the friction and resulting heat to simply overwhelm the engine and ruin it permanently. That’s called catastrophic engine failure, and it’s one of the many problems that engine oil is designed to prevent.
To operate safely, every engine needs a certain amount of oil within it at any given time. This is the oil level we have referred to. Oil levels can be reduced by oil leaks, as well as oil burning off which can happen when the engine isn’t in optimum condition. Over time, oil also becomes contaminated by metal shavings, dirt, grit and other things that the oil picks up from the engine as it works. The filter removes most of these impurities but eventually, it gets to the point where it can’t. This is the point where you need an oil and filter change.
Contaminated oil is more viscous, and clogged with nasty debris, which is why it becomes less effective both as a coolant and as a lubricant. The oil level sensor and oil pressure sensor can’t tell us the condition of the oil, but will at least tell us about how much oil we have and if it’s moving at the right rate.
What is an Oil Level Sensor? How Does it Work?
The oil level sensor is a long, thin instrument that is installed vertically into the oil pan from below. It sits in the oil and continuously measures the oil level both when status and when moving. The way it works is quite simple in essence. If the oil level drops below a predetermined level, then the sensor will signal the ECU to activate an oil warning light on the dashboard.
Most oil level sensors work using an electrical resistance method. The less of the sensor that is covered by the oil, the bigger the change in the resistive value. More modern and luxury-brand cars use cutting-edge ultrasonic sensors with a piezoelectric transducer that sends pulses into the oil itself to get back echos. This information is then fed to the ECU.
Some cars will have an added restricted power mode that will not even allow you to start up the engine if the oil level is currently too low.
Symptoms of a Failing Oil Level Sensor
- Differing Reading to the Dipstick
If you are warned of low oil levels, the best thing to do is follow up with a manual check using your dipstick. If you do 2-3 dipstick checks and they all seem to negate the oil level sensor reading, then in all likelihood you have a faulty sensor.
- Oil Warning Light Going On and Off Sporadically
A real warning on oil level should be a steady and consistent oil warning light on the dash. If the warning comes and goes, only staying on for a short time, then the sensor needs attention.
- “Check Engine” Light (CEL) Comes On
If you see a CEL warning, then one of the many potential things that it could be is warning you that the sensor is faulty and in need of repair or replacement.
What is an Oil Pressure Sensor? Where is it?
The oil pressure sensor is located on the engine block of your car, and it monitors the rate at which oil is traveling to and through the engine. If pressure is dropping, it can indicate all kinds of problems, such as oil leaks, a bad sump, and so on. Loss of needed pressure means that the engine likely isn’t getting all the oil that it needs, and thus will suffer nasty consequences.
The location of the oil pressure sensor is invariably somewhere on the engine block, but its exact position depends on your car’s make and model. In most cases, it’s near the bottom of the cylinder head, but it can also be installed right on the cylinder head if design permits. You might also identify it from it having an attached block connector, and either a single or pair of thin wires attached to it.
Symptoms of a Failing Oil Pressure Sensor
- Sporadic Warning Light
Similar to the oil level sensors, sporadic appearing and disappearing of the oil warning lights is the first and most common sign of a problem with the oil pressure sensor.
- Excess Noise but No Warning
When oil pressure is low, it generates a great deal of excess noise in the timing chain and within the engine in general. If you hear such noise, but don’t see the oil warning light, it could mean that the sensor is faulty.
- Oil Leaks from the Sensor
The pressure sensor has oil pouring through it at all times, but sometimes the sensor can develop leaks via its threads or even through the body of the sensor itself.
Is it Safe to Drive with Low Oil Level/Pressure?
In a word, no. Oil has to be both at the right level and moving through the engine at the right pressure in order to do its job, which is to be the lubricating and cooling lifeblood that stops the engine failing. It’s akin to asking if the human body can function with much less blood or too low blood pressure. There’s a reason you’re not meant to drive after donating blood!
If you discover your car is either leaking oil, or exhibiting other signs of low oil levels or oil pressure, it’s best to call a mechanic to tow your car to an auto shop for repairs.
Oil Level Sensor & Oil Pressure Sensor – Replacement Cost
Replacing the oil pressure sensor is usually cheaper than the oil level sensor. According to numbers from repairpal, you can expect to pay anywhere between $50-250 for an oil pressure sensor, and from $480-580 for an oil level sensor.
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