We are not talking about the high-speed wobble you get from an unbalanced tire on the highway. We are talking about that annoying, jerky vibration you feel when you are turning the wheel at low speeds, like when you’re pulling into a parking spot. Mechanics call this "steering judder."
It feels like the power assist is cutting in and out rapidly, fighting your hands. If you ignore it, you risk damaging the pump or the rack seals. Here is the checklist to track down the cause.
1. Air in the System (Aeration)
This is the number one cause of steering vibration. Hydraulic systems rely on fluid being non-compressible to transfer force. Air, however, compresses. If air bubbles get trapped in your rack or lines, the pressure fluctuates wildy, causing the steering to "stutter."
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Check the fluid: Open the reservoir while the engine is running. If the fluid looks pink and foamy, or you see bubbles surfacing, you have air in the line.
- The Fix: You need to bleed the system. Jack up the front wheels to take the weight off. With the engine off, turn the steering wheel from lock to lock (all the way left, then all the way right) slowly about 15-20 times. This pushes air out to the reservoir.
2. Belt Slip and Tension
The power steering pump generates the pressure that the rack needs. It is driven by the engine’s serpentine belt. If that belt slips—even for a micro-second—the pump stops creating pressure, and your steering goes heavy. When the belt grabs again, the steering gets light. This rapid on-off cycle feels exactly like a vibration.
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Inspect the belt: Look for a "glazed" or shiny surface on the ribbed side of the belt. Shiny means it has lost its grip.
- Check the tensioner: If you have an automatic belt tensioner, check if it is bouncing excessively while the engine idles. A weak tensioner cannot hold the belt tight when the power steering pump is under load (like when parking).
3. Sticky Spool Valves (Dirty Fluid)
Inside the steering rack, there is a precision component called the rotary spool valve. It directs fluid to the left or right side of the rack piston based on where you turn the wheel.
If your power steering fluid is old, black, and full of sludge, this valve can physically stick. It momentarily hangs up before snapping open.
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The diagnosis: If the belt is tight and there is no air, check the fluid color. Dark fluid suggests contamination.
- The Fix: A full fluid flush. Cleaning out the sludge often frees up the valve and smoothes out the operation.