Overactive braking
I have owned a 2005 E91 330d Touring automatic for five years and it is currently showing 80,000 miles. Over the past year, it has developed a brake fault. This occurs when you gently press the brake pedal to bring the car to a halt from any speed; despite this, the car seems to apply sudden pressure to the braking system within a few feet of stopping. To passengers it feels like the driver has pushed the brake pedal hard just before the car has stopped. I have flushed the system with fresh brake fluid using a Sealey VS820 brake bleeder pressure system and checked for fault codes against my code reader, but there is none showing, along with no fluid loss. The car stops in a straight line and has passed its last MOT with very even brake balance in this state.
My second issue is that I would like to change the ‘sealed for life’ gearbox oil, but the Haynes manual refers you to BMW as it uses a manufacturer-specific oil. Can you tell me if it is possible to change the oil myself? If so, what oil should I use and is there a drain plug? Finally, how much oil do I require? Colin Truman Regarding your first query, this sounds very much like an overactive brake servo drawing the brake on excessively. I have experienced this on other vehicles. Although BMW have no listing for such a fault on their troubleshooting chart, this is worth checking. You may be able to determine if the problem is the servo by disconnecting the vacuum pipe to the servo and jacking up one wheel.
With the engine running, get an assistant to spin the wheel while you gently apply the brakes. You should be able to slow the wheel down without it suddenly locking up. Remember that without servo assistance the brake will be harder to apply. If full control is possible with the vacuum pipe connected, this would confirm that the servo is drawing the brake on too aggressively when applied.
The gearbox oil used by BMW is Shell M1375.4 (BMW part number 83 22 0 142 516); this can also be purchased as ZF Lifeguard 6. BMW do not recommend mixing oil, and as some oil will be retained within the torque convertor, it is not possible to change all of the oil without removing the gearbox.
To change the oil you will need to remove the gearbox sump, which also contains the built-in filter. New sump/ filter kits with a gasket and seven litres of ZF Lifeguard oil are available on ebay for around £180. You should have the plastic sump on your vehicle, as opposed to the metal version.
Refilling the ’box will be via the level plug in the gearbox. After filling, the engine will need to be run up and the gear lever moved through all gear positions twice. Then, with the vehicle in 'Park', the gearbox level needs to be topped up with the engine running – best done over a pit or on a secure ramp.
Finally, BMW recommend the level is checked using the BMW DIS (Diagnosis Information System).