* Ball Joint: A worn or damaged ball joint is a very common cause of knocking sounds, especially when turning. The increased stress on the joint during reverse and left turns would exacerbate the noise.
* Tie Rod End: Similar to a ball joint, a worn tie rod end allows excessive play in the steering linkage. This play can manifest as a knocking sound under stress, particularly during turning maneuvers.
* CV Joint (Constant Velocity Joint): While less likely to knock *only* in reverse and left turns, a failing CV joint, particularly the outer joint on the passenger side, could contribute. The angle of the joint changes significantly during turning, making it a suspect. A clicking or popping sound is more typical of a CV joint, but a knock is possible, especially if significantly worn.
* Wheel Bearing: A worn wheel bearing can cause a variety of noises, including knocking. However, it's less likely to be isolated to only reverse and left turns. A wheel bearing usually makes noise regardless of direction.
* Steering Rack Bushings/Mounts: Worn bushings or mounts in the steering rack can create knocking sounds, particularly under stress like turning.
* Loose components: Something might be loose in the suspension or steering system. This could be a bolt, bracket, or other component that's rattling against something else.
Troubleshooting Steps:
1. Visual Inspection: Carefully inspect the passenger-side front wheel area for any obvious signs of damage, looseness, or wear in the components listed above. Look for grease leaks (CV joint), play in the ball joint or tie rod end (try to move them by hand – you shouldn't feel significant movement), and anything that appears loose or damaged.
2. Jack Up and Inspect: Safely jack up the vehicle and support it with jack stands. This allows for a more thorough inspection of the suspension and steering components. Again, check for play in the ball joints and tie rod ends. Rotate the wheel and listen for any unusual sounds from the wheel bearing.
3. Professional Inspection: If you're not comfortable performing these inspections yourself, take your van to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately.
Important Note: Driving with damaged suspension or steering components is dangerous. If you suspect a problem, have it repaired as soon as possible.
