TL;DR
- Oil pressure (Bentley): at least 0.5 bar at idle; regulated pressure on the six-cylinder 4.0 bar at elevated engine speed.
- Capacity: 6.5 litres with a filter change (M50 and M52).
- Low pressure means a worn pump, worn bearings or severe engine wear: all major repairs. Test with a gauge before deciding anything.
- Oil pan removal on cars built after September 1992 requires supporting the engine from above and lowering the front suspension crossmember.
How it works
On the six-cylinder, the oil pump is mounted to the engine block in the oil pan area and driven by a chain and sprocket; the sprocket nut has a left-hand thread. The pump draws oil through a pickup tube in the pan and feeds the engine through the filter in the oil filter housing, which also carries the oil pressure switch.
Checking the warning light and switch (Bentley)
- Ignition on, engine off: the oil pressure warning light must come on.
- Unplug the switch: the light must go out. If it stays on, the wire to the switch is shorted to ground somewhere.
- If the light doesn’t come on with the ignition on: ground the switch connector with a jumper wire. If the light then comes on, test the switch. If not, the fault is in the wiring to the cluster or the bulb.
- The switch itself: an ohmmeter between its terminal and ground should show continuity with the engine off and no continuity with the engine running, when oil pressure opens it.
If the light stays on with the engine running, check the oil pressure and don’t drive the car until the cause is found: the engine may be severely damaged.
Measuring oil pressure
- Check the oil level first. For the most accurate result, the oil and filter should be new and the correct grade.
- Remove the oil pressure switch from the oil filter housing (some oil will drain) and fit a pressure gauge in its place.
- Start the engine and check the pressure cold and hot.
| Condition | Specification (Bentley) |
|---|---|
| Idle, minimum | 0.5 bar |
| Regulated pressure at elevated engine speed (six-cylinder) | 4.0 bar |
Low pressure points to a worn or faulty oil pump, worn engine bearings or severe engine wear. All of these need major repairs, so confirm the measurement with a good gauge before tearing the engine down. Thicker oil isn’t a fix.
Capacity and oil
| Engine | Oil with filter change (Bentley) |
|---|---|
| M50 | 6.5 L |
| M52 | 6.5 L |
| S50US | 6.5 L |
| S52US | 6.0 L |
Use the grade and specification BMW lists for your car, and change the oil regularly: an old engine of unknown history deserves shorter intervals rather than longer ones.
Oil pan removal (six-cylinder)
- Cars built after 9/92 have a different front suspension crossmember. Removing the oil pan requires supporting the engine from above and unbolting and lowering the front crossmember.
- The dipstick guide tube is sealed with an O-ring: check it comes out with the tube, and fit a new one.
- The oil pickup is involved in the job; Bentley notes the pickup tube is refitted with a new gasket.
Refitting:
- Clean every sealing surface completely and fit a new pan gasket.
- Apply a bead of sealer (3-Bond 1209 or equivalent, about 3 mm wide and 2 mm high) at the joints where the pan gasket meets the end cover and the front timing case cover.
- Tighten the front pan bolts first, then the rear.
- Fill with oil, start the engine and raise it to about 2,500 rpm until the oil pressure light goes out (about five seconds).
Oil pump
The six-cylinder pump comes out with the oil pan off: remove the sprocket nut (left-hand thread) and lift the sprocket off with its drive chain, unbolt the pickup tube from the pump, then unbolt the pump from the block.
| Fastener | Torque (Bentley) |
|---|---|
| Oil pump to engine block (M8) | 22 Nm |
| Oil pump sprocket nut (M10×1, left-hand thread) | 25 Nm |
| Oil pan to block, M6 grade 8.8 / 10.9 | 10 / 12 Nm |
| Oil drain plug, M12 / M22 | 25 / 60 Nm |
| Oil filter cover (M8) | 25 Nm |
Inspect the pickup screen while you’re in there: sludge or debris on it says a lot about the engine’s past, and pieces of black plastic point to the timing chain guides. See the timing chain guide.
Hard driving and track use
The standard pan is designed for road use. For sustained hard cornering or track days, owners commonly fit a baffled oil pan or an oil accumulator to keep the pickup covered. Whatever you fit, keep the oil level at the full mark, and check the pressure with a gauge after any change to the system.
