How Do You Know If the Oil Pressure Gauge Is Bad?

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The oil pressure in a vehicle engine plays an important role in making sure that lubricants reach the areas they need to, including the camshaft, main, and balance shaft bearings. This helps reduce the wear of engine parts, ensuring that the engine does not get too hot and continues to run smoothly. When checking the oil pressure gauge, keep in mind that the pressure reads higher in cold weather due to the higher thickness (also known as viscosity) of the oil.

How the oil pressure gauge works

The inner workings of an oil pressure gauge depends in large part on the type: electric or mechanical. A mechanical gauge uses a spring that is affected by the pressure of the oil. A coiled tube, called a bulb, attaches to the oil pressure gauge's outer casing and to linkage at the bottom of the needle. Oil is fed into the bulb under pressure, the same as in the vehicle engine, from a supply pipe that causes the bulb to attempt to straighten. This pressure is what moves the oil pressure needle on your dashboard showing the oil pressure level in the engine.

An electric gauge uses a sending unit and a circuit to send electric signals to the gauge via a wire-wound coil. These parts allow the system to alter the indicator needle to show the correct pressure. The oil enters the end of the sensor and pushes against a diaphragm, which moves a wiper inside the sensor up and down a resistance blade, creating the signal that moves the needle in the gauge.

Some vehicles use an oil warning light instead of an oil pressure gauge. In this case, the warning light connects to a sensor that uses a simple on/off switch that reads the oil pressure through a diaphragm attached to the engine.

Symptoms of a bad oil pressure gauge

When an oil pressure gauge stops working properly, ask a mechanic to make sure it is not faulty. Some common indicators that the oil pressure gauge is not working correctly include:

  • Oil pressure gauge not working: The causes for this range from a faulty gauge to the need for an oil change. Have a mechanic check the oil level.

  • Oil pressure gauge reading too low, generally below 15 to 20 PSI while idling. Cold weather can also make the oil pressure read low until the oil pump has had a chance to deliver the oil to the engine.

  • Oil pressure gauge reading too high, or over 80 PSI while driving, especially at higher RPMs. Vehicle owners can check their manuals for specifics on how high the oil pressure gauge reading should get to when running their engine at certain RPMs.

Other causes of a high or low oil pressure gauge reading

In addition to a bad oil pressure gauge, problems with other systems and parts within the engine can cause a high or low reading. A mechanic will check these problem areas to ensure these parts remain in good working order and are not causing the oil pressure problem.

  • The oil needs changing: Over time, oil breaks down and loses some of its viscosity, causing a low reading on the oil pressure gauge. The mechanic will check the condition of the oil and change it if necessary.

  • A blocked oil filter can cause an oil pressure gauge to read high: The mechanic will replace the filter and change the oil in this case.

  • A blocked oil gallery can also cause a high reading: If this happens, a mechanic flushes the oil system while changing the oil.

  • Sometimes the wrong grade of oil causes the oil pressure to read high. The mechanic will make sure that your vehicle has the correct grade of oil and change it to the proper grade if necessary.

  • Worn bearings sometimes cause the oil pressure to show a low reading. The mechanic will change the bearings if needed.

  • A broken oil pump may cause a low oil pressure reading. In this instance, a mechanic will replace the oil pump.


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Recent Oil Pressure Light is on Inspection reviews

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Number of Reviews

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Rating Summary
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Jeffrey

25 years of experience
846 reviews
Jeffrey
25 years of experience
BMW 323i - Oil Pressure Light is on Inspection - Charlotte, North Carolina
Jeffery was great. His job was to diagnose a low oil pressure issue with my 2000 BMW 323i. Jeffery was thorough, researched the problem, kept me updated with his progress and answered any questions I had along the way. Unfortunately, the repair that I needed was a bit extensive and is not offered by My Mechanic. However, if it was a project the service offered, I would definitely want Jeffery to do the job.
Toyota Highlander - Oil Pressure Light is on - Charlotte, North Carolina
Jeffrey was able to determine the problem right away and, although he didn't have the replacement part on hand, was able to install the new part and perform the oil/filter change less than an hour after the diagnostic. As with our past experiences with Jeffrey, things went smoothly and my car is happy again!

Breck

18 years of experience
541 reviews
Breck
18 years of experience
Chevrolet Tahoe - Oil Pressure Light is on - Spring, Texas
This is my second appointment with Breck. He is very professional, taking time to answer my questions and explain the issues with my vehicle. I am very pleased and will use Breck/Your Mechanic again.
Oldsmobile 98 - Oil Pressure Light is on - Houston, Texas
The mobile mechanic came. I must say I am impressed! He found my house. He and I started talking. He said he owned two Ninety Eights previously. He was there to look at my Oldsmobile Ninety Eight. He had two Oldsmobile Ninety Eight Touring Sedans. The ones he owned were from the 1987-1990 era. He was describing the floor shifters and they had and how much he liked Ninety Eights, Touring Sedans, and the Oldsmobile Eighty Eight LSS too. He talked about how a family member owned one and how he was fixing his. He talked in detail about the Touring Sedan and the things he loved. He asked me how long had I owned my Ninety Eight. I told him 2003. He told me how he become a mechanic and went to school for it and more. He got into the Ninety Eight and it would not start. He got out and disconnected the battery and rubbed the negative and positive battery terminals together. He reconnected them and the Ninety Eight started! The instrumentation then told him exactly what it was. There is a sensor at the bottom of the oil pan. He said by doing what he did with the terminals, it cleared the computer and reset it. We went underneath the car and he showed me the sensor. He said which one did you replace? I told him. He said you were on the right path. You know what you are doing. You need to replace this sensor and not the one you did. You can get the sensor and replace it because it is clear you know what you are doing and on the right path. He said you also need to replace your valve cover gaskets. They are leaking. I told him I will request him to come back and do that. I am not doing that even thought I can.

Matt

13 years of experience
23 reviews
Matt
13 years of experience
Mazda MPV - Oil Pressure Light is on - Tempe, Arizona
Very happy with the service I received with Matt. He took the time to learn about my vehicle history and maintainence as well as explaining all my options regarding his diagnosis. Absolutely will recommend him and call him again regarding any car issues I may have down the road.

Andrian

30 years of experience
78 reviews
Andrian
30 years of experience
BMW 528i - Oil Pressure Light is on - Pompano Beach, Florida
Andrian was early for the appointment. Very knowledgeable and put my mind at ease immediately. We scheduled the repair together after his diagnosis and I look forward to working with him in the future

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