A couple weeks ago I started my car and heard the engine clatter for a few seconds until it built up oil pressure. I thought maybe it was low on oil, so I shut it down and checked the level, but the oil was on point. I restarted the car -- no noise -- so I drove to work and back. The next time I drove the car, the engine made that "low oil" clatter for a second or two before it quieted down. I drove about 15 blocks and the engine developed a knock. This is a '95 L-36 with 45k miles on the car. I bought it in April with 41k from the daughter of the (deceased) original elderly owner. About 1500 miles ago, the LIM gaskets, and UIM were replaced. The UIM was original and hadn't failed. The LIM gaskets were on their way out, but hadn't totally failed yet.

We left on a 3000k mile road trip the next week, and had planned to drive the Olds since it gets better gas mileage than the GXP. We wound up taking the GXP, and it was a blast on the road trip (gotta love the extra power at sea level -- I live at 5300' in elevation) I towed the '95 to a mechanic I trust, and he finally got a chance to look it over yesterday. He pulled the oil pan and said the #1 crankshaft bearing was bad. He said the others looked okay, which tells him that it hadn't run low on oil. I know the car's UIM hadn't yet failed.

What could've caused the failure? He said that it might be that the crank wasn't perfectly round from the factory, but that he didn't have any real idea what caused it. I'm also wondering what all will need to be replaced. He's looking into a "crank kit" that would replace the crank and bearings. I know I'll want a new oil pump since the old one has probably sucked up metal from the failed bearing. I'm worried that the metal from the bearing could've circulated through the engine and caused other damage. I've changed the oil and filter twice on the car in the past 4k miles, and I'm hoping the filter did it's job. Any thoughts or suggestions?

This is something I figured I wouldn't have to deal with for at least 150k more miles.

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'91 Olds 442 w-41 (1 of 204): '79 Olds Holiday 88 coupe. Factory buckets, console
1958 Impala Coupe 348 75k miles
1958 Impala convertible 283, 51k miles

I would suspect the UIM you removed was a replacement, and not the original on the car. This would mean the original failed and did some minor damage to the rod bearings that got worse over time.

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#1 crank bearing, or #1 rod bearing? I'm sure it's possible, but I've never heard of a main bearing spinning on these engines. Somewhat rare, I'd think. But that's beside the point. You need to find out how bad the bearing is. If it spun a lot, you could have babbit material all through the engine if the bearing was destroyed. Could have clogged the oil filter, forcing the bypass to open, flooding the engine with lovely bearing material. If this is the case, the engine really needs to be dismantled and boiled. If you caught it in time and it just spun a little and didn't lose any material, you're prolly OK.

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