Oil Pressure — General Information and Troubleshooting

Normal Oil Pressure Values

The 944 oil pressure should run 4–5 bar73 psi at idle when the engine is cold. As the oil warms to normal operating temperature, pressure will gradually decrease to 2–3 bar44 psi at idle. At normal operating temperature and 5,000 rpm, oil pressure should read approximately 4 bar58 psi.

Oil takes longer to reach normal operating temperature than coolant — do not be surprised if oil pressure continues to decline after the coolant temperature gauge has stabilised.

To confirm a reading against the factory thresholds with a mechanical gauge, see the oil-pressure figures and gauge check.

Reading the Gauge

Sending unit (gauge reads high)

Pegged high (5 bar73 psi) or will not read below 4 bar58 psi at operating temperature: this indicates a likely problem with the oil pressure sending unit, not the oil system itself.

Very occasional dip below 2 bar29 psi: can occur on very hot days after extended hard driving — not necessarily a fault.

Warning: Oil pressure below 1 bar15 psi is cause for serious concern. It indicates a problem with either the oil pressure indication or the oiling system itself. Do not drive the car until the cause is determined and corrected.

Causes of low oil pressure

Gauge and sending-unit failures are rare; genuinely low oil pressure normally indicates an actual problem with the oiling system. Work down the troubleshooter above, then read the matching cause.

Failed oil pressure relief valve

One method of diagnosis is to remove the relief valve and briefly crank the engine to verify that oil exits the relief hole. Oil coming out confirms a relief-valve problem. No oil, or very little, from the hole suggests a problem with the pump itself. For the plug torque and the piston wear check when you have the valve apart, see the lubrication-system service data.

Loose crankshaft pulley bolt

The crankshaft bolt applies force to a spacer that tensions the gear driving the oil pump. If the bolt is loose, the gear will not turn the pump.

Broken oil pump pickup tube

Normally caused by excessive vibration when the motor mounts are bad. The oil pan must be removed to replace the tube.

Worn main and/or rod bearings

Oil pressure that tracks normally through the range but reads lower than normal throughout typically points to a leaking relief valve or worn main/rod bearings.

Oil pump lost prime

If no oil pressure is indicated when the car is started, the oil pump may have lost its prime. To re-prime:

1. Remove the oil filter.
2. Pour oil down the centre hole of the filter mount while rotating the crankshaft counter-clockwise.
3. Install a new oil filter.
4. Start the car and verify oil pressure.