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I have a 08 Chevrolet Impala with a 3.5 with 70k miles. There is a tick that corresponds to engine speed. It's a pronounced tick but I highly doubt its piston slap or rod knock. It seemed like an exact match for a noisy lifter. I replaced lifters and same thing.

The noise seems to come from the upper part of the motor, maybe slightly to the rear, below the plenum. Oil level is fine and no low oil pressure light.

What else could cause engine tick?

Video may tell more

https://youtu.be/EZjPWnCwGTk

UPDATE: Pulled the rod on #6 and found this on the bearing.enter image description here

Touching the crank, feels smooth. Nothing like the rod bearing. Need to mic it though.

UPDATE 2 : Several rod bearings are similar to this but not quite as bad. Main bearings are fine. What could have caused this?

  • Google for GM 3.5 piston slap. I think you'll find that these engines may indeed have piston slap. If it was rod knock, you would probably know it, so I would rule away rod knock. – juhist Jan 25 at 17:51
  • Could a noisy fuel injector make that sound? – asp316 Jan 25 at 20:16
  • Yes it could, I used to have 1989 Opel Vectra with noisy injectors. However, the noise could be heard only with the hood open. You couldn't hear it to the inside of the car with the hood down. If the noise can be heard inside the car, I don't believe it's injectors (unless they are extraordinarily noisy). – juhist Jan 25 at 20:27
  • I'd probably put a vacuum gauge on it and do a running compression test on each cylinder. That does not sound like a noisy injector. – Ben Jan 26 at 2:30
  • Disconnecting spark plug from #6, the noise goes away. Guess I'm getting into it. Anyone know how hard it is to pull the oil pan? Hoping to work on just that cylinder. – asp316 Jan 26 at 21:54
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Wow!

What do the crankshaft rod journals look like? That's some serious bearing damage.

What caused it? Hard to say, other than a lack of lubrication. Which may have been promoted by piston slap...

I would be replacing ALL the lower end bearings, and potentially having the crank pulled and polished/reground if there is anything short of a mirror finish on any crankshaft bearing surface.

Also, what does the top end of the #6 rod look like? I'd knock out the wrist "gudgeon" pin and check the bushing. Perhaps that is what is causing your tick.

  • Rod journals look fine and mic fine, oddly enough. What's odd is the wear pattern is in a specific spot of the worn rod bearings. I was expecting the wear to be across the whole bearing. What would cause that? – asp316 Feb 8 at 14:11

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