: Northstar oil pump failure

02-08-12, 08:16 AM
We recently fixed a lower case leak on a '93 Allanté. We had to flood the pump to restore oil pressure. Even after that, on a test drive the oil pressure looked low once it warmed up. Aftermarket oil pressure sensors often show "0" oil pressure in a '93 Allanté, so I suspected that could be the problem. But it had a Delco sensor. Then a mechanical gauge showed about 2 lbs oil pressure at idle. We decided to pull the oil pump. What we found was quite surprising- the outer ring had split into 6 pieces, and there was a small crack in the pump case. Apparently at some point something had passed through the pump to cause this. The cracks in the outer ring were not fresh. Over the years we have run into two other '93 Allanté Northstars which experienced what Cadillac engineering refers to as "catastrophic low end failure". When we experienced the first case back in 2005, I was told to look at the crank journals with the missing pistons to see if they were blue or not. They were blue, which showed loss of oil pressure. This was on a 76k mile well maintained one owner car. Then about a year ago we went through the same scenario on another '93 Allanté, 77k miles, well maintained, catastrophic low end failure. Blue crank journals again. We did nothing to investigate what might have happened to cause loss of oil pressure, instead focusing on what had to be done to replace the blown engines. I wish I had both of those blown engines back to check the oil pumps. Has anyone else been through something like this? I am thinking we may have gotten very lucky this time, to catch the problem before this engine self-destructed.