The purpose of this report is to quantify the methodology for evaluating and isolating rattle noises in power rack & pinion steering systems. In today's ever changing market of vehicle body & suspension changes, it's very important that the correct process be used to identify the correct noise source. The results of this evaluation procedure will help sort out the difference between hydraulic generated noises and mechanical generated noises.The process used in sorting the hydraulic noise from the mechanical noise is through the use of a “standpipe”, which dampens the hydraulic reaction pulse in the hydraulic steering system. We refer to this hydraulic pulse as “hydraulic rattle”, and is often confused with mechanical rattle during vehicle evaluations. The concept of the standpipe is similar to that used in household plumbing, which reduces the effects of hydraulic hammering in the water pipes.