Answer
Feb 13, 2026 - 09:16 AM
When the power steering suddenly disappears on a W163 ML 320, there are three main things you need to look at right away. First, pop the hood and check your serpentine belt; if it snapped or slipped off, the pump won't turn. Usually, if that belt is gone, you’ll also notice your battery light come on and the AC stop working, since they all run off that same loop.
If the belt is still intact, check your fluid level in the reservoir. These specific models are notorious for a leaking O-ring where the reservoir meets the pump, which can let air into the system or eventually drain it dry. If the fluid is low, top it up with the correct Mercedes-approved hydraulic fluid and inspect for wet spots around the hoses, the pump body, and the steering rack boots.
If you've got plenty of fluid and the belt is spinning but the wheel is still rock hard, the internal seals on the pump have likely failed. This manual provides the complete factory troubleshooting tree to confirm the fault, along with the step-by-step instructions to replace the power steering pump or the steering rack. It gives you the exact torque specs and hose routing you need to get that hydraulic system sealed back up and working properly.
