Power Steering Noise: Causes & Fixes

"Hi everyone,

My Superb 3U 77KW TDI has been making noises in the power steering system during steering movements for some time. There are no visible leaks externally. With the engine running and the power steering reservoir cap open, there's a significant amount of oil overflowing. This doesn't happen in a comparable vehicle. I've already replaced the power steering pump and the steering rack, including the check valve. Unfortunately, this didn't solve the problem. The oil overflow is still present. The parts are from TRW. I've blown out all the lines. I've noticed that there's a valve or calibration device in the return line to the power steering reservoir. I've also considered the possibility of air being drawn in, but I haven't found anything. In my opinion, the oil overflow is caused by a faulty valve. What do you think about this problem?"

Is the pipe bent or somehow constricted? If it's making a loud hissing/rattling noise, it could also be due to cavitation in the pump.

If the oil isn't foaming like in your mom's soup, then you probably don't have a problem with air in the system. I also think that a faulty pressure relief valve is causing the cavitation, which is producing the noise.