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Randall C
Randall C, ASE Certified Technician
Category: Car
Satisfied Customers: 12803
Experience:  32 years Foreign / Domestic Cars All aspects of Diag and Repair
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1999 Oldsmobile Aurora: engine knock..main bearing..used engine

Customer Question

I have a 1999 Oldsmobile Aurora 4.0 that gradually developed an engine knock that sounds like a main bearing. Everyone seemed to have a different idea what it was, but all agreed that the repair would cost more than the car was worth. When it had registered 125,000 miles, I located a used engine with 60,000 miles and had it replaced. THE NOISE WAS STILL THERE !
Theories varied but the most popular notion was that noise was probably coming from the transmission charging pump. The frequency (tone)of the knock seemed to bear that out, so a low-mileage transmission was installed. Nothing changed.
We replaced the belt tensioner, the idler pulley, the air conditionong compressor and the tensioner for the water pump belt. The noise is still there and getting worse.
The car now has 182,000 miles on it and I love it. I want to get rid of the noise and drive it another 100,000 or so
What can you tell me about the 4.0L engine, because I think I got two with the same problem
Submitted: 7 years ago.
Category: Car
Expert:  Randall C replied 7 years ago.
Hello, at any point did you run engine with belt off to see if noise left or stayed?
Customer: replied 7 years ago.
Finally, after everything else was tried
Expert:  Randall C replied 7 years ago.
Did the flywheel AND the torque converter get replaced?
Customer: replied 7 years ago.
Expert:  Randall C replied 7 years ago.
This engine does not have any know inherant problems with bearings or noises. There was a recall for head bolt holes drilled too deep causing premature headgasket failure. I am not ther hearing the noise but if stethescope is being used on oilpan and noise is internal,. you have changed engines.trans converter, flywheel removed belt etc and it clearly sounds like bearing noise, then this is most likely what it is. I do not have any explanation as to why 2 engines. You may want to place block of wood under oilpan and gradually jack up engine while running to see if lifting up on mounts and changing engine ride postition changes the tome indicating something other than engine. I wish I had more info. You could also try unbolting the torque converter and pushing it back and running the engine short while to see if noise remains. if so, clearly nothing trans related.
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