Component Tests and General Diagnostics
WM 170301 Checking oil pressure
Tools
Technical values
Preliminary work
Information
If vehicles have fault entries relating to oil pressure, oil pump activation, oil pressure monitoring, etc. in the DME control unit (and a warning light comes "on" on the instrument cluster), proceed as follows:
- Check the oil level.
- Delete related faults.
- Do not replace components, such as the oil pump, oil pressure sensor or oil pressure control valve if you suspect that they are faulty.
If the vehicle has not been driven for a long time (months), the control mechanism in the oil pump can become stiff ("stick").
Very short trips and a lot of loading/manoeuvring can cause the oil to become very diluted => Oil pressure very low. For example, 20 cold starts in quick succession can reduce the viscosity of the engine oil by 30%.
- Change the engine oil. Test-drive the vehicle.
- If error messages/warnings are displayed again, proceed in accordance with the instructions under Guided Fault Finding in the PIWIS Tester.
Information
- The oil pressure can be displayed and checked for any engine speeds using the PIWIS Tester.
- The pressure readings can be shown graphically in the data logger.
- If an oil-pressure gauge needs to be connected for further tests, proceed according to the instructions starting from "Preliminary work".
- For details of measured values, see below.
1. The adapter can be fitted without removing the Y-shaped pipe on naturally aspirated engines.
2. On turbo engines, remove Y-shaped pipe at the right and air box for air cleaner ahead of the throttle valve to create unrestricted access to the oil pressure sensor. -> 243519 Removing and installing air box for throttle housing (Y-shaped pipe ahead of throttle valve) 243519 Removing and installing air box for throttle housing (Y-shaped pipe ahead of throttle valve) and -> 242719 Removing and installing air box for air cleaner 242719 Removing and installing air box for air cleaner
Air cleaner outlet on turbo engine, right
Tools and materials
Tools
Oil pressure tester
Checking oil pressure
WARNING
Toxic substances
- Danger of poisoning or suffocation
-> Ventilate the work area well.
-> Never ingest or inhale.
-> Read specific information on the Hazard Sheet.
-> Wear personal protective gear.
WARNING
Hot fluid
- Danger of scalding
-> Let the fluid cool down.
-> Wear personal protective gear.
WARNING
Highly inflammable or explosive materials
- Danger of fire or explosion
-> Avoid contact with hot parts or sources of ignition.
-> Use suction to remove ignitable vapours.
-> Attach warning sign in a clearly visible position.
Information
The oil pressure may be too low for a number of reasons:
- Oil is diluted (e.g. fuel gets into the oil due to too many cold starts without warming up the engine afterwards).
- Oil pump is faulty.
- Too much bearing clearance (e.g. crankshaft bearing).
- Oil level is too low.
- Oil pressure regulating valve is faulty.
- Oil pressure sensor is faulty.
- Incorrect oil has been used. Use only oil that has been approved by Porsche for the measurement.
Information
The oil pressure may be too high for a number of reasons:
- Oil has thickened or is very cold after a cold start and high engine speeds.
- Oil pump is faulty.
- Mechanical oil pump pressure relief valve is faulty (oil pump needs to be replaced).
- Oil pressure regulating valve is faulty.
- Cable plug of oil pressure regulating valve has fallen off or open circuit between it and the control unit (oil pressure may be up to 11 bar, engine loses approximately 10 kW of engine power)
- Oil pressure sensor is faulty.
- Incorrect oil has been used. Use only oil that has been approved by Porsche for the measurement.
1. Remove screw plug at the measuring point -5-. When doing so, make sure that the sealing ring -6- does not fall off. Soak up emerging engine oil with a cloth.
Oil pressure sensor and oil pressure measuring point
2. Screw adapter for oil-pressure gauge -1- with sealing ring -2- into the measuring point. Carefully tighten to max. 10 Nm (7.5 ftlb.).
Adapter in measuring point
Adapter setup
3. Screw oil-pressure gauge -3- onto the adapter -2-. Counter screw torque using an open-ended wrench -1-.
Oil-pressure gauge on adapter
4. Move oil-pressure gauge upwards into position. When doing this, make sure the hose is not touching any rotating components. => Oil-pressure gauge set down securely
Oil-pressure gauge set down securely
5. Complete motor for taking measurements.
6. Check that there are no rotating components touching the measuring hose and that the pressure gauge is easy to read when positioned.
Oil-pressure gauge set down securely
7. Connect the PIWIS Tester. Connect battery charger.
- Use the PIWIS Tester to call up the actual values for oil pressure, engine temperature and engine speed in DME. The oil pressure displayed in the PIWIS Tester is always higher than that on the pressure gauge by the value of the ambient pressure (depending on the altitude, e.g. 1000 hPa).
- The pressure display on the oil-pressure gauge must be the same as the value on the PIWIS Tester once adjusted by the ambient pressure value.
- The pressure display on the oil-pressure gauge is much slower than that on the PIWIS Tester. The measured value on the PIWIS Tester fluctuates rapidly. The trend between the two measuring instruments is significant.
- The measured oil pressure remains virtually constant over different rev ranges. The measurement using the oil-pressure gauge merely confirms that the oil pressure sensor's display is correct.
- The pressure readings can be shown graphically in the data logger.
8. Start the engine and let it run until it reaches the measurement temperature. => Engine temperature: 90°C Measured values (examples)
- For a cold start (e.g. 24 °C), pressure immediately jumps to 8 bar briefly (oil-pressure gauge).
- Following cold start, oil pressure drops briefly to 3 bar (oil-pressure gauge) - 4000 hPa (PIWIS Tester).
- For warm-up phase at idle speed, pressure drops from 3 bar to 1.8 bar (oil-pressure gauge) - 4000 hPa drops to 2800 hPa (PIWIS Tester).
- At engine temperature of 90 °C at idle speed, 1.5 bar to 1.6 bar (oil-pressure gauge) - 2600 hPa (PIWIS Tester).
- At engine temperature of 90 °C at 1000 rpm, 2.8 bar (oil-pressure gauge) - 3800 hPa (PIWIS Tester).
- At engine temperature of 90 °C at between 2000 rpm and 4000 rpm, the oil pressure is almost constant at 3.0 bar (oil-pressure gauge) - 4000 hPa (PIWIS Tester). The value may fluctuate by 0.1 bar (100 hPa).
Subsequent work
1. Remove oil-pressure gauge and adapter again.
2. Refit screw plug with a new sealing ring.
3. Fit Y-shaped pipe or intake pipes ahead of the throttle valve. -> 243519 Removing and installing air box for throttle housing (Y-shaped pipe ahead of throttle valve) 243519 Removing and installing air box for throttle housing (Y-shaped pipe ahead of throttle valve) and -> 242719 Removing and installing air box for air cleaner 242719 Removing and installing air box for air cleaner