OE Power Steering pumps on 1996-1999 Northstar Cad DeVilles operate at a different pressure-flow rate at low RPM compared to all present day " Genuine" GM replacement pumps, new or remanufactured. The " newest" lower pressure pumps cause the PS to become incredibly " stiff" when jockying in and out of tight spaces, engine at near idle, and rapid wheel motions required. Or in an emergency situation to get out of tough traffic when stopped at a light, etc. This has been proven by my certified repair shop several times by installing TWO new pumps which exhibit this sluggish operation, and finally a known good USED pump by performing several double swap tests. The mechanics were dumbfounded at the swap test results!
So GM must have changed their specs somewhere after the original stuff was marketed, and now in the replacement market, apparantly for uniformity's sake, anything available through the parts supply chain operates to the new specs. The ONLY way to get a pump that supplies sufficient pressure at near idle speeds is to get a KNOWN GOOD OE pump from a junk yard.
So now to the question. How do I contact a GM Service Technical person to get into Cadillac's Design Engineering department to ask how and why the engineers reduced the pressure/flow rate on later pumps, and then retroactively spec'd that back as far as 1996? Perhaps for better gas mileage? Cheaper pump vanes, etc? If the flow pressure/rate was diddled via a restrictor, it would seem fairly easy to return a present day pump to a 10 year old pressure spec. HOWEVER, if it was done by impellor redesign, then no hope, and it's back to the junk yard solution. Thanks in advance. Tom
Friday, April 28th, 2006 AT 8:12 PM