My mom has a 1997 Bonneville SE, and this morning when she went to go to work, there was a terrible sound sort of like rod knock going on, but when I got close to the engine, it sounded more like it was coming from the top end, or around the cam area. Are bad bearings on the 3.8'* common, leading to rod knock, or are there any known top end problems that cause this problem? What about water pump bearings giong bad and causing that knocking noise? The car has 18?,000 miles on it, and has been fairly regularly maintained.

pushrod maybe but most likely as noisely lifter

I thought about it maybe being a lifter, but this is very loud. I could hear it inside the house with the car parked outside. I was told it may be a stuck of collapsed hydraulic lifter. If thats it, what would the process be for replacing it? I assume the engine has to come out.

if its that loud its its a rod knock !!!!!! how is the oil ? changes often? was the upper intake replaced?

Oil changes were done regularly. In fact it is due for another oil change and she was going to take it in this afternoon. It had the upper intake replaced last summer, it went and stranded my sister in the middle of the night.

i thought my knock was a lifter or timing chain or something 2 . i pulled the oil pan off and pulled #1 rod cap off and there it was i fixed the crank as good as i could and put a new rod bearing it and it quieted it for 3 months and just last week i put another on in it and it lasted a day till it started to knock again my guess its a rod

only reason why i asked if upper intake was replace cuz antifreeze could have contributed to this problem by geting in the lower half of the motor

Well the last thing you wanna do is take it to a mechanic. lol