If your car is making strange noises or you’re seeing warning lights on the dashboard, it could be a sign that there’s something wrong with the oil sending unit. Let’s find out what does bad oil sending unit looks and sounds like and how to replace it.
Bad oil sending unit symptoms can include low oil pressure readings, engine knocking, and inconsistent oil gauge readings. If the oil sending unit is not functioning properly, it can cause serious engine damage.
Table of Contents
What is an Oil Sending Unit?
An oil sending unit is a small device that regulates the flow of engine oil to the engine. It is located between the oil filter and the engine or inside the oil pan. The device consists of a small valve that controls the flow of oil.
The sending unit is responsible for ensuring that the correct amount of oil is delivered to the engine and monitors the engine’s oil level. If the oil level drops below a certain point, the sending unit will activate a warning light on the dashboard to alert the driver.
How does it complete its job? Let’s find out in the next section, shall we?
How Does an Oil Sending Unit Function?
The oil sending unit consists of a float, an electrical switch, and a resistor. The float is connected to the electrical switch, and the switch is connected to the resistor. The output of the float switch is converted into an electrical signal, and a wire carries the signal to the warning light or gauge.
The purpose of the oil sending unit is to measure the engine’s oil level and then send a signal to the dashboard gauge that tells the driver how much oil is left in the engine.
The float rises and falls with the engine’s oil level, and as it does, it activates or deactivates the switch. When the switch is turned on, it sends a signal to the resistor, which tells the gauge how much oil is in the engine.
If the float is low, the switch will be turned on for a longer period, and the gauge will read “LOW.” If the float is high, the switch will be turned on for a shorter period, and the gauge will read “FULL.”
As the engine runs, the float drops lower as oil is used and circulated through the engine. When it gets to a certain point, usually about a quart low, the sending unit sends a signal to the light or gauge telling it to turn on. This warns the driver that the oil level is getting low and needs to be checked.
Understanding the Construction of an Oil Sending Unit
To better understand how an oil sending unit works, it’s helpful to know a little bit about its construction. The float, resistor, and everything are housed inside a plastic housing with two terminals.
- G Sender Output: This is the signal sent to the gauge.
- Ground: This is where the ground wire is connected.
And then, on the other side, there is a 1/8″ NPT thread for installation purposes. Now let us see how these terminals connect to the oil pressure gauge on the other side.
The oil pressure gauge has four wires coming out of it. Let’s see where each of these wires go and come from.
- Green Wire: This wire goes to the sending unit output terminal and sends the signal to the gauge.
- Black Wire: This is the ground wire, and it goes to the sending unit’s ground terminal.
- Red Wire: This is the power wire, and it goes to the ignition switch.
- Yellow Wire: This wire goes to the oil pressure warning light. It illuminates the light when the oil pressure is low.
Bad Oil Sending Unit Symptoms
Now that we know how it’s constructed let’s move on and talk about the symptoms of a bad oil pressure sensor.
- Check Engine Light
- Fluctuating Oil Pressure Gauge
- Low Oil Pressure Warning Light
- Blinking Engine Oil Pressure Light
- Strange Noise
These symptoms might give you a hint but let’s analyze each one of these for the sake of our understanding:
1. Check Engine Light:
The check engine light is one of the most common symptoms of a bad oil sending unit. If the sending unit is not working properly, it will cause the check engine light to come on. The light may come on and stay on, or it may blink.
This is because if the sending unit is not working properly, it may not be able to send the correct signal to the engine control module (ECM). This can cause the ECM to think there is a problem with the engine oil level, which can trigger the check engine light.
Additionally, a bad oil sending unit can also cause the ECM to receive an incorrect oil pressure reading. This can also trigger the check engine light. However, there are various other reasons why your check engine light may come on.
That’s why it is important to pay attention to this warning sign. The light could indicate a minor problem, such as a loose gas cap, or a more serious issue, such as a faulty oxygen sensor.
2. Fluctuating Oil Pressure Gauge:
Another symptom of a bad oil sending unit is a fluctuating oil pressure gauge. The sending unit is responsible for sending a signal to the gauge that indicates the level of oil pressure in the engine.
If the sending unit is not working properly, it can send a false signal to the gauge, causing it to fluctuate. This can be very dangerous because it can lead to the engine being overworked and damaged. There are a few other things that could cause this fluctuation.
One potential cause of a fluctuating oil pressure gauge is simply a dirty or old oil filter. If the filter is clogged, it can restrict the oil flow to the engine and cause the pressure to drop. Replacing the filter should fix the problem.
Another possibility is that there is an issue with the oil pump itself. If the pump isn’t working properly, it won’t be able to maintain the correct pressure in the system. This will usually require a professional to fix.
No matter the cause, if you notice your oil pressure gauge fluctuating, don’t ignore it!
3. Low Oil Pressure Warning Light:
The low oil pressure warning light is another symptom of a bad oil sending unit. This oil light is usually located on the dash and illuminates when the engine oil pressure drops below a certain level.
If the sending unit is not working properly, it may not send the actual oil pressure signal to the light, causing it to come on. Additionally, a bad oil sending unit can also cause the light to come on even when there is no oil pressure problem.
This can be very confusing and frustrating because it can make it seem like there is a problem when there isn’t one.
4. Blinking Engine Oil Pressure Light:
If you see the engine oil pressure light on your dashboard blinking, it is an indication that the oil pressure in the engine is very low. Or some sensor or oil pressure sending unit has gone bad.
If you see this light blinking, it is important to take action immediately. Turn off the engine and check the oil level. If the oil level is low, add more until it reaches the full line.
If the oil level is fine, then there may be a more serious problem, and you should take the car to a mechanic to check it out.
5. Strange Noise:
If your car’s engine makes a strange noise, it could be caused by a bad oil sending unit. The oil sending unit is responsible for sending oil pressure information to the engine control unit (ECU).
If the unit isn’t working properly, the ECU won’t be able to regulate the engine’s oil pressure properly. One of the most common symptoms of a bad oil sending unit is strange noises from the engine.
These noises can range from a faint tapping noise to a loud knocking noise. You hear large knocking noises because the oil pressure drops too low, causing the engine’s parts to rub together. If you hear a light tapping noise, it could be due to fluctuating oil pressure.
What Causes Oil Sending Unit to go Bad?
There are a few different things that can cause an oil sending unit to go bad. A few of the most common causes are:
1. Wear and Tear:
One of the most common causes of a bad oil sending unit is simply wear and tear. These units are not built to last forever, and they will eventually start to fail.
As they age, they become less accurate and more likely to fail. Over time, the moving parts inside the unit can become worn down, causing the unit to fail.
The most common cause of wear and tear is the constant exposure to heat and pressure. This can cause the seals to break down and leak, which will eventually lead to the unit failing.
2. Oil Leaks:
Another common cause of a bad oil sending unit is oil leaks. If there is an oil leak, it can get into the unit and damage it. Oil leaks can be caused by several things, such as a faulty gasket or seal.
If these parts are not working properly, they can allow oil to leak out. Once the oil gets into the unit, it can damage the sensitive parts and cause the unit to fail.
3. Not Changing Oil Regularly:
If you don’t change your oil regularly, it can cause the oil sending unit to fail. Old oil can become sludge-like and clog up the unit. Over time, as engine oil breaks down, it can cause deposits to form on the oil sending unit.
If these deposits build up too much, they can prevent the oil sending unit from functioning properly. This can ultimately lead to the unit going bad. To avoid this, it’s important to make sure you keep up with your regular engine oil changes.
4. Malfunctioning Oil Pump:
If you have a bad oil pump, it can cause the oil sending unit to fail. The oil pump is responsible for pumping oil through the engine. If it isn’t working properly, it can starve the engine of oil and cause damage.
On the contrary, if it is pumping too much engine oil, it can cause the oil to become diluted. When oil passes through the sending unit with pressure much higher than expected, it can cause the unit to fail.
Oil Pressure Sensor Vs. Oil Sending Unit; Differences Highlighted
An oil pressure sensor is a device that monitors the oil pressure in an engine. The sensor sends a signal to the engine control unit (ECU), which then adjusts the amount of fuel and air mixture being delivered to the engine based on the amount of oil pressure.
If there is not enough oil pressure, the ECU will reduce the amount of fuel being delivered to prevent damage to the engine. Oil pressure sensors are important for ensuring that engines are operating at peak efficiency and avoiding costly repairs.
On the other hand, an oil sending unit is a device that monitors the oil pressure and sends a signal to the gauge on the dash. It consists of a float, which rises and falls with the engine’s oil level, and a switch that sends a signal to the gauge.
The main difference between an oil pressure sensor and an oil sending unit is that an oil pressure sensor sends information to the ECU. In contrast, an oil sending unit transmits information to the oil pressure gauge.
However, the basic function of both devices is to monitor the oil pressure in an engine and prevent damage.
How to Replace an Oil Sending Unit?
If you think your oil sending unit is going bad, it’s important to replace it as soon as possible. Thankfully, this is a relatively easy process that most people can do themselves. Let’s get started!
1. Park the Vehicle:
Park your vehicle safely on a level surface and turn off the engine.
2. Disconnect the Negative Battery Cable:
To prevent any electrical shorts, disconnect the negative battery cable first.
3. Locate the Oil Sending Unit:
The oil sending unit is usually located on the side of the engine block near the oil filter.
4. Remove the Wiring:
Remove the wiring from the oil sending unit. Be careful not to pull too hard on the wires, as you don’t want to damage them. Keep tagging each wire you remove so you know where it goes back.
5. Remove the Unit:
Use a ratchet or wrench to loosen the threads that hold the unit in place. Be careful not to drop the unit, as it can be damaged easily.
6. Install the New Unit:
Install the new unit by hand-tightening it in place. Then, use a ratchet or wrench to finish tightening it.
7. Reattach Wiring:
Reattach the wiring to the new unit and reconnect the negative battery cable.
8. Test the Vehicle:
Start the engine and check for any leaks. If everything is working properly, you should see the oil pressure gauge on the dash move when the engine is running.
Oil Sending Unit Replacement Cost
Replacing the oil sending unit is neither difficult nor expensive and, in most cases, can be done by the average do-it-yourselfer.
The cost of the replacement unit itself ranges from $30 to $60 and another $10 to $20 for miscellaneous hardware such as seals, washers, and nuts.
Depending on the make and model of your vehicle, you may also need a special socket or wrench to remove the old unit. This means the total cost of replacing an oil-sending unit should be between $70 and $130.
If you plan to take your car to a mechanic for this replacement, expect to pay somewhere between $131 and $200. Labor costs are estimated between $58 and $74, while parts are priced at $73.
While this job is not difficult, it does require special tools to remove and replace the unit. These tools can be expensive, so many prefer a mechanic to do the work.
The oil sending unit is an important part of your car’s engine because it helps you know when to add more oil. When your engine’s oil level gets low, it can cause serious damage to your engine.
A bad oil sending unit can cause your oil pressure gauge to give false readings or not work. This can lead to engine damage if the problem is not fixed promptly.
If you think your oil sending unit might be going bad, it’s important to have it checked out by a mechanic as soon as possible.
Did this blog post help you understand what a bad oil sending unit is and what the symptoms are? Let us know in the comments below.
Frequently Asked Question?
Are the oil pressure switch, sending unit, and sensor all the same?
No, the oil pressure switch, sending unit, and sensor are not all the same. However, they all serve the same purpose; to monitor the oil pressure in an engine.
An oil pressure switch is a mechanical device that uses a diaphragm to turn the engine’s oil pump on and off. An oil sending unit is an electrical device that sends a signal to the oil pressure gauge on the dash.
A sensor is a device that measures the oil pressure and sends a signal to either an oil pressure switch or sending unit. Sometimes, sensors can be used in place of an oil pressure switch or sending unit.
How do I know if my oil sending unit is bad?
A few symptoms can indicate your oil sending unit is going bad. These include:
- The oil pressure gauge on the dash is not working.
- The oil pressure gauge is giving false readings.
- The engine is making strange noises.
- There is an oil leak coming from the engine.
If you notice any of these symptoms, it’s important to have your car checked out by a mechanic as soon as possible.
How long does it take to replace an oil sending unit?
Replacing an oil sending unit is a relatively quick and easy job that most people can do in about an hour. However, it can take longer if you don’t have the right tools.
What happens when an oil sending unit fails?
When an oil-sending unit fails, the engine may overheat and cause damage to the internal components. The engine will also run less efficiently and may produce more emissions. In some cases, the engine may stall or fail to start.
Can you drive with a bad oil sending unit?
Though you can drive with a bad oil sending unit, it’s not recommended. A bad oil sending unit can cause your vehicle to run low on oil, leading to engine damage. You should have the unit checked and repaired as soon as possible if you think it may be failing. Driving with a bad oil sending unit is not advisable and could result in expensive repairs.
What is the average lifespan of an oil sending unit?
Like all other sensors and electrical switches, the lifespan of an oil sending unit can vary. However, most units will last for the life of the vehicle if they are well-maintained.
Do you need to drain motor oil while replacing the oil sending unit?
You do not need to drain the motor oil while replacing the oil sending unit. You will only need to remove the old unit and install the new one in its place.
What is an oil pressure switch?
An oil pressure switch is a switch that is activated by the oil pressure in an engine. The switch turns on when the oil pressure reaches a certain level and turns off when the pressure drops below that level.