The brief
Mr Lek's Passat had loud rattling noises coming from underneath when he drove, so he brought it in for us to find the source. A rattle from under the car means something in the suspension has worn loose, and loose suspension doesn't just rattle, it lets the car move where it shouldn't and wears its neighbours. The control arms locate the wheels, and they pivot through bushings, rubber or polyurethane cushions that absorb road shocks, soak up the movement in the joints, and keep things quiet. Over the years a bush perishes and tears, and once it has play the control arm shifts when it shouldn't, which is the rattle. A worn bush doesn't tighten back up, so it gets replaced.
The diagnosis
On the lift a thorough inspection traced the rattle to the control arm bush, worn and torn so the arm had play, which is the noise from underneath. The rest of the suspension was sound. That's a control arm bush replacement with the geometry checked, rather than chasing a rattle that's only going to get louder.
The work
The worn control arm bush was dismantled out and a new genuine VW-spec bush fitted, every fastener torqued to the manual figures and the suspension bolts done up at ride height so the new bush isn't pre-loaded. With it in, the front geometry was checked and set back to spec. A road test confirmed the rattle gone, the front tight, the steering precise, and the car tracking straight, all turned around in a day.
The outcome
No rattle from underneath, the front tight, precise steering, even tyre contact, and the car tracking straight, returned in a day. Mr Lek got the Passat back quiet again. A worn control arm bush only gets noisier and starts wearing the alignment about, so replacing it and checking the geometry put the front right in one go.
