What are the symptoms of a faulty BMW torque converter?
3 Answers
Common symptoms of a faulty BMW torque converter mainly include five types: excessively high torque converter oil temperature, excessively low torque converter oil supply pressure, torque converter oil leakage, excessively low vehicle speed or lack of power during driving, and abnormal noises during operation. Causes of torque converter failure: Excessive wear gap in the left and right sealing rings on the turbine shaft and guide wheel seat, causing internal oil leakage, poor oil inflow and return in the torque converter, excessively high torque converter oil temperature, the torque converter pump wheel failing to effectively transmit power to the turbine, damage to the overrunning clutch of the first or second guide wheel, reducing or disabling the power transmission function of the guide wheel, etc. Functions of the torque converter: Clutch function: When the engine is idling, the torque converter acts as an unengaged clutch between the engine and the transmission; torque amplification function: it increases torque by combining "high pump wheel speed" with "low turbine speed" to generate greater starting and driving torque; hydraulic coupling function: under non-idling or non-starting conditions, it acts as a hydraulic coupling to transmit engine torque to the transmission; lock-up function: when the turbine speed rises to match the pump wheel speed, the lock-up clutch engages, and the torque converter transmits engine power to the transmission in a 1:1 ratio.
When repairing cars, I often encounter issues with BMW torque converters. The main symptoms include the engine revving up high during acceleration, but the car doesn't move forward, feeling like it's slipping or idling. Noise is particularly noticeable during low-speed turns or uphill climbs, with a constant buzzing sound. Sometimes, the steering wheel shakes violently, especially during cold starts or in traffic jams, and gear shifts become sluggish, jerky, or fail to engage smoothly. These symptoms are often caused by internal wear of the torque converter or aging transmission fluid, leading to power transmission failure. During diagnosis, it's essential to check if the fluid is discolored or insufficient, and regular maintenance can prevent these issues. Once these problems arise, immediate repair is necessary; otherwise, the entire transmission could be damaged, leading to skyrocketing repair costs.
After driving my BMW for a long time, the most obvious sign of torque converter failure is when the car body jerks violently a few times upon starting, and then pressing the accelerator feels like stepping on air—the RPM surges but the speed doesn't increase. The noise is particularly loud when reversing, as if the engine is struggling. There's a noticeable lag during gear shifts, feeling like the power isn't connecting smoothly, and sometimes it even stalls suddenly. These symptoms stem from torque converter fluid seal failure or internal blade damage. Timely action is crucial, such as changing the transmission fluid and minor repairs, which can save a lot of money. As a long-time owner, I recommend regular checks on the transmission's condition and avoiding hard acceleration to extend its lifespan.
