Engine Oil Pressure – What Everyone Needs To Know

The first indication of trouble may be a flickering oil light or low engine oil pressure reading on a dash gauge.

If the warning goes unnoticed or is ignored, the next clue that something is wrong may be valve clatter as the hydraulic lifters or lash adjusters are starved for oil and ingest air.

So, A loss of engine performance, excessive engine noise, and even poor starting can all be caused by abnormal engine oil pressure.

Engine Oil Pressure
Engine Oil Pressure

When the engine oil pressure is too low, premature wear of internally lubricated parts can be one of the results.

Any of these problems should cause you to break out your mechanical oil pressure gauge and get a reliable reading.

All engines will lose a certain amount of engine oil pressure over time as normal wear increases engine bearing clearances.

Unusually low engine oil pressure in an engine regardless of mileage is often an indication that something is seriously wrong.

So anytime a vehicle has a low oil pressure condition, don’t delay in investigating the cause.

In addition, problems with other systems and parts within the engine can cause a high or low reading.

Engine Oil Pressure Gauge
Engine Oil Pressure Gauge

Common Causes Of Low Engine Oil Pressure:

Low Oil Level

  • The most obvious reason for the low oil indicator to come on, is the oil level actually being low. The first course of action would be to check the oil level in the engine. If the level is indeed low, you could top up the oil, and hear your car purr with joy!

Overheating of Engine Oil

  • The low oil indicator also tends to light up when the oil gets too hot, and thins out.

Worn Engine Bearings

  • In a high mileage engine, low oil pressure is often due to worn main and rod bearings. The oil pump itself does not create pressure. It produces flow and the resistance to that flow produces pressure. As the bearings wear, clearances increase allowing increased flow which reduces pressure.

Worn Oil Pump

  • Another common cause of low oil pressure is wear or excessive clearances inside the oil pump. Too much clearance inside the pump will reduce the pump’s ability to pump oil efficiency, which reduces flow and pressure.

Oil Pump Pickup Screen

  • Consequently, Restrictions in the pickup tube screen can choke off the flow of oil into the pump, reducing flow and pressure. Even a relatively small amount of varnish buildup on the screen can restrict oil flow at higher engine speeds. As a result, A coating only .005 inch thick on the screen will reduce the total “open” area of each hole to .030 inches, causing a whopping 44 percent reduction in oil flow!

Weak or Leaky Engine Oil Pressure Relief Valve

  • The pressure relief valve, which may be located on the pump body or elsewhere on the engine, can be yet another cause of low oil pressure if the valve sticks open or is held open by a small piece of debris. The valve opens when pressure reaches a preset value (typically 40 to 60 psi). This vents oil back into the crankcase and limits maximum oil pressure in the engine. The reason for doing so is to prevent oil pressure from reaching dangerous levels. Too much oil pressure can be just as bad as too little. Consequently, Excessive pressure can rupture the oil filter or even blow out pressed-in oil galley plugs in the block.

Faulty Engine Oil Pressure Gauge

  • Sometimes the oil pressure gauge itself can be at fault. If you find that the gauge shows low pressure after changing oil, there could be a problem with the guage. Replacing the oil pressure gauge should solve the problem.

Aerated Oil

  • Low oil pressure may also be the result of air in the pump. This normally happens when the bottom of the crank churns the oil in the sump, which is an indicator that you have too much oil in your engine. Bubbles in the oil prevent it from lubricating the moving parts properly.

Dirty Oil and Engine

  • Sometimes the engine may become starved for oil at higher speeds because the oil is not returning quickly enough to the crankcase. The underlying cause here is usually severe varnish buildup that restricts the oil return holes in the head.

Oil System Leaks

  • Leakage between the oil pickup tube and pump, as well as between the pump and block can also suck air into the pump. It is not unusual to find engines where the pickup tube has fallen completely off, causing a complete loss of oil pressure.

Plugged Oil Filter

  • A plugged oil filter can be yet another cause of low oil pressure. All filters create a certain amount of resistance to flow that increases with the rate of flow. But the amount is not much, typically only a couple of pounds. But as the filter becomes clogged with debris, the restriction created increases. Eventually no oil will pass through the filter element. So to prevent such a blockage, most filter have a pressure relief valve located in the filter. This allows the oil to bypass the filter and keep on flowing. Replacing the plugged filter will solve the problem.

Engine Oil Pressure Test Gauge
Engine Oil Pressure Test Gauge

Engine Oil Pressure Testing-Using A Mechanical Engine Oil Pressure Gauge

Pressure can be tested by temporarily installing a mechanical oil pressure gauge in place of the sending unit.

Step-1

  • Bring the engine up to operating temperature.
  • Now shut the engine off.
  • Locate the oil pressure sending unit; usually it is on the lower side of the engine block.
  • Disconnect the wire from the sending unit and remove the sender.
  • Install the oil pressure test gauge into the hole where the sender was removed.
  • Check the engine’s oil level and fill, if required.

Step-2

  • Now start the engine and check the oil pressure on the gauge.
  • Watch as the engine warms to note any excessive drops due to temperature.
  • Record the measured oil pressure, then turn off the engine.
  • Compare the test results with the manufacturer’s specifications.
  • If the oil pressure is within specifications, this shows that the oil pressure sending unit may not be working correctly.
  • In many cases, replacing the oil sending unit will correct the problem.
  • After the test is complete, reinstall the oil pressure sending unit, start the engine, and confirm there are no leaks.

Consequently, Without engine oil pressure an engine will experience extreme internal engine damage due to heat caused by friction.

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About Danny Bender 156 Articles
DannysEnginePortal.com Is The Premier Automotive Engine Troubleshooting Resource Site. DannysEnginePortal.com Shares Information On Engine Troubleshooting, Engine Rebuilding, Engine Repair Tips, Tech Info, Basic Machining, Automotive Testing, In Addition To Possible Solutions.