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What To Do If Your Engine Oil Pressure Warning Light Is On

by Larry Carley copyright AA1Car.com

engine oil pressure warning light If the engine oil pressure warning light is on, it may mean your engine has lost normal oil pressure. STOP driving immediately and turn your engine off. Your engine can be severely damaged if oil pressure is low or zero.

Symptoms of Low Oil Pressure

Oil Pressure warning light on or flashing

Oil pressure gauge reading very low or zero

Ticking, rattling or knocking sounds from your engine

Sudden loss of engine power or misfiring

Possible Causes of Low Oil Pressure Gauge Reading or Warning Light:

A low oil level (check the dipstick)

Worn oil pump

Worn engine main/rod bearings

Serious engine oil leak (gaskets, seals, cam plugs or oil filter)

Defective oil pressure sending unit (oil pressure may be okay but the gauge is not reading correctly)

Defective oil pressure gauge or warning light switch (oil pressure may be okay but the gauge or switch is defective)

Oil Pressure Warning Light Diagnosis

First, determine if the oil is full or low by checking the dipstick. NOTE: On some engines, there is an oil level sensor in the engine's oil pan that will turn on the oil warning light if the oil level is low. If the dipstick shows a low oil level (the oil level is at or below the ADD line, or no oil can be seen on the dipstick), your engine may be leaking oil, burning oil or both. Add oil as needed, restart the engine and see if the engine now has normal oil pressure (normal gauge reading or oil pressure warning light off).

Check the dipstick. If low, add oil and inspect your engine for leaks.

Oil leaks are a common cause of oil consumption and a low oil level in the engine. Oil leaks can occur at the valve cover, oil pan or timing cover gaskets, overhead camshaft end seals or plugs, or the front or rear crankshaft oil seal. Inspect the top, sides and bottom of the engine for signs of oil leakage. Look for greasy stains, heavy accumulations of grease, or oil dripping on the ground. The higher the miles on the engine, the more likely the gaskets and seals may be leaking. If your engine is leaking oil because of a bad gasket or seal, the leaky gasket or seal should be replaced.

oil leak locations
Oil can leak past old gaskets and worn seals.

If the outside of the engine is clean and there are no obvious oil leaks, and the oil level is low, your engine is probably burning oil because the piston rings, cylinder, valve guides or valve guide seals are worn. This may be the result of high mileage wear or neglect (not changing our oil often enough to prevent wear). Oil consumption problems such as these can be expensive to fix because it may require rebuilding or replacing the engine.
NOTE: On many engines, replacing the valve guide seals will significantly reduce oil burning if the original guides and seals are worn.

If the oil usage is not too severe (say less than one quart of oil every 1000 miles), check your engine dipstick often and keep adding oil as needed to prevent the oil level inside the engine from getting too low. If the engine is using a lot of oil (say more than a quart every 500 miles), check the dipstick constantly every time you fill up with gas. Carry some oil with you in the trunk of your vehicle and add some oil as needed to maintain the oil level in the engine above the ADD mark. The bad news is that your engine is on its last legs and will likely need to be overhauled or replaced soon.

worn oil pump causes  low oil pressure
Internal pump wear and leaks can cause a loss of oil pressure.

Bad Oil Pump?

If the oil level is between ADD and FULL, and the engine was making noise when it was running, the problem may be a worn or defective oil pump that cannot maintain normal oil pressure. DO NOT run the engine until the pump can be replaced. Oil pressure can be checked by attaching a pressure gauge to the port where the oil pressure sending unit screws into the engine block. If oil pressure is within specifications (typically 10 psi for every 1000 rpm) the oil pump is okay and the problem is likely a bad oil pressure sending unit. If pressure is less than specifications, the oil pump may be worn, or the engine bearings may be worn.

If the oil level is between ADD and FULL, and the engine was running normally (no noise) after the oil pressure warning light came on, the problem may be a defective oil pressure gauge, sending unit or warning light switch. You can probably start the engine and drive the vehicle home or to a shop for repairs. But if your engine begins to make loud ticking, rattling or knocking noises, STOP and shut off the engine.

Low Oil Pressure Fixes

If the oil level is low, add oil to the engine to bring the level up to the FULL mark on the dipstick. DO NOT overfill the crankcase. Use the type of oil viscosity specified in the vehicle owners manual.

If the oil pressure gauge reading remains low or the oil pressure warning light remains on, remove the oil pressure sending unit on the engine and connect a pressure gauge directly to the engine. Start the engine to see if the pump is generating adequate pressure. If pressure is normal (about 10 PSI for every 1000 RPMs of engine speed, the problem is not a bad oil pump, but a faulty oil pressure sending unit. Replace the oil sending unit.

If you do not have a pressure gauge for testing oil pressure, try replacing the oil pressure sending unit with a new one. If the oil pressure warning light goes out or the gauge reading is now normal, you have fixed the problem. But if the warning light or low gauge reading continues, the problem is likely a bad oil pump.

If the oil pump is worn or defective (does not produce adequate pressure), the oil pump will have to be replaced. The gears inside the pump and the pump housing and cover will wear over time, so low oil pressure on a high mileage engine (over 100,000 miles is not unusual). Also, sometimes debris in the crankcase can be sucked into the pump and prevent the oil pump bypass valve from fully closing. This will also cause a loss of normal oil pressure.

On many engines, the oil pump is located inside the oil pan on the bottom of the engine. The pan must be removed to replace the pump. This may require raising the engine and/or removing steering or suspension components that are in the way so the pan can be removed. On other engines, the oil pump is located inside the timing cover on the front of the engine. The pump has a large internal gear that slides over the crankshaft and is driven by the crank. Disassembly requires removing most of the components on the front of the engine to replace the pump. This type of pump is much more difficult and time consuming to replace.

If oil pressure is low because of worn engine bearings, the crankshaft bearings will have to be replaced. This usually requires overhauling or replacing the engine.

book More Engine Oil Related Articles:

Troubleshooting Low Oil Pressure

Oil Pump Diagnosis

Motor Oil Viscosity

Diagnosing Engine Noise

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