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Weird knocking noise coming from engine

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New User

Oct 21, 2021, 7:16 PM

Post #1 of 4 (810 views)
Weird knocking noise coming from engine Sign In

Hi everyone. I have a really weird knocking noise coming from my cars engine (series 2 3800, car is 04 LeSabre)
Here is a video:
The noise happens at 7 seconds in after i rev and it comes back to idle, then goes away.

It happens consistently but under very specific circumstances. It happens when the engine is warm, i have just gotten off the gas and just hit idle. There is no noise at all at higher than idle rpm and no noise after sitting at idle for a while. So i hear it any time I pull up to a stop sign, traffic light, etc. Running AC amplifies it.
Pretty much totally stumped on this. Any ideas would be appreciated!

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Oct 21, 2021, 11:30 PM

Post #2 of 4 (799 views)
Re: Weird knocking noise coming from engine Sign In

It's weird alright? This makes that "clickable" > < it's there now what is it?
Check oil of course or better yet if this is new, change oil to another but interested in the sludge situation if you can tell?
Noises are tough almost always but sounds of an oil knock (be scared if so) as if there's a loss of oil pressure, perhaps it can't return to oil pan quickly enough?? IDK.
There's a chance it isn't really engine itself but something close that is being bumped fooling us what and where the source really is.

Pay attention and if it gets worse or better with an oil change note that.
BTW, I don't like that noise it's an older car you didn't say miles on it but smacks of worn or abused in some way to cause that would NOT set out on some trip with this with that,


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 22, 2021, 3:30 AM

Post #3 of 4 (784 views)
Re: Weird knocking noise coming from engine Sign In

Try something for me.

Get a yellow tire marking crayon and go to the harmonic balancer and draw a line from the center out to the edge of the pulley. Now start the engine and rev it once or twice. Shut the engine off and look at the line you drew and see if the line is broken.

I've had a few of this particular engine with a broken harmonic balancer causing a noise like that.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

New User

Oct 22, 2021, 10:00 AM

Post #4 of 4 (767 views)
Re: Weird knocking noise coming from engine Sign In

Ah gotcha. I purchased the car used it had like 164k miles on it now it's at 172k. No clue how the last owner drove it but I've been babying the car to try and make sure it lasts longer. It does burn oil but i get it changed religiously every 3 months and check it regularly. I've had the noise for a while when it first started it was so faint every shop i took it to said they didn't hear anything even though I could have sworn it was there and now it's at a point where it's really noticable and concerning.

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