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Knock after head gasket replacement

Tiny
JDOT6
  • MEMBER
  • 2004 CHEVROLET MONTE CARLO
  • 3.8L
  • V6
  • TURBO
  • 2WD
  • AUTOMATIC
  • 186,000 MILES
I took my car into the mechanic for a head gasket replacement, paid almost $1,800.00 in total, they replaced the gaskets, took the heads and had them machined and stuff. I pick the car up and upon starting it the car hesitated to start, and acted like it wanted to stall, and then a knock started. Could the knock be caused from them changing my head gaskets or are they not held reliable?
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Monday, March 1st, 2021 AT 7:07 PM

17 Replies

Tiny
JDOT6
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  • 11 POSTS
There was no sign of any knock before I took the car in.
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Monday, March 1st, 2021 AT 7:16 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Is it a knock or more of a tick? I'm not sure what would have been done to cause it by changing the gaskets, but there could be something related to one of the valve.

If it is loud enough to be recorded, record it and upload it for me to hear. Also, here is a link that describes different engine noises. See if you find one that mirrors what you experience.

https://www.2carpros.com/articles/engine-noises

Let me know. Also, let me know if you have other questions.

Take care and God Bless,

Joe

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Monday, March 1st, 2021 AT 7:42 PM
Tiny
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Definitely more of a knock.
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Monday, March 1st, 2021 AT 7:45 PM
Tiny
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They told me they took the heads, had them resurfaced and pressure tested they were fine. Just something seems not right here how my car ran fine besides the bad head gaskets, I have them repair it and now it knocks? And didn’t want to start when I picked it up from them.
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Monday, March 1st, 2021 AT 7:46 PM
Tiny
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My supercharger boost gauge is also stuck in the middle now as well, not sure what they did to cause that or if that could have caused a knock?
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Monday, March 1st, 2021 AT 7:53 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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The supercharger had to be removed. See if you can tell if that is where the sound is coming from. I attached a pic of it below.

Let me know,
Joe
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Monday, March 1st, 2021 AT 8:31 PM
Tiny
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In my opinion it definitely sounds like it’s coming from the lower end of the engine.
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Monday, March 1st, 2021 AT 8:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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It does sound like an engine bearing. Does it change when you rev the engine or it is under a load?
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Tuesday, March 2nd, 2021 AT 11:29 AM
Tiny
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Gets louder definitely.
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Tuesday, March 2nd, 2021 AT 12:57 PM
Tiny
JACOBANDNICKOLAS
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Have you made contact with the shop that did the work? Have they had a chance to check and listen to it?

Joe
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Tuesday, March 2nd, 2021 AT 1:33 PM
Tiny
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Yes, they just listened to it, assumed it was a knock, said I need a new engine or block. Said they did their part right and there was nothing they could do.
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Tuesday, March 2nd, 2021 AT 4:19 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
This is going to be a difficult one to prove. Let's try this. Let's see if we can confirm what the noise is coming from.

By any chance, is the check engine light staying on while the engine is running? If it does, have the computer scanned for diagnostic trouble codes. Here is a video showing how it's done:

https://youtu.be/b2IJGfImVvw

If you don't have a scan tool, often times a parts store will do it free of charge. If this needs to be done, make sure to write down the codes found for me.

Next, and don't laugh, go to a parts store and purchase an automotive stethoscope. They are not at all expensive, under 10 dollars. Then, with the engine running, see if you can determine what portion of the engine the sound is coming from. Check on top of the supercharger, valve covers, and so on. Pay special attention to the valve covers. It could be something that went wrong in the cylinder head.

Let me know what you find.

Joe

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Wednesday, March 3rd, 2021 AT 3:54 PM
Tiny
NICKOLAOSF
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Hi JDOT6,

We can help you with this information. First I would recommend a video with sound to verify rod knock or lifter knock. This sounds like you have a lifter issue, before we jump to conclusions please send video with sound try to verify failure.
I am glad to help you. If there is anything else we can help you with please contact us again. Thank you for choosing 2CarPros.
Cheers, Nick
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Wednesday, March 3rd, 2021 AT 7:56 PM
Tiny
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Here’s another video:
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Wednesday, March 3rd, 2021 AT 8:06 PM
Tiny
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And another.
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Wednesday, March 3rd, 2021 AT 8:07 PM
Tiny
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I think maybe my supercharger belt is worn. Pulleys are loose or the supercharger bearings, or the supercharger coupler.
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Wednesday, March 3rd, 2021 AT 8:08 PM
Tiny
NICKOLAOSF
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It sounds like lower end noise. If when you raise the idle the noise is heavier, you have lower end noise (rod knock). There is a possibility for your blower to have a failure. Determine by removing the drive belt and listen again.
Cheers, Nick
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Wednesday, March 3rd, 2021 AT 8:31 PM

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