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Knock/rattle at idle only

Tiny
OUTTALUCK
  • MEMBER
  • 1999 CHEVROLET MALIBU
  • 3.4L
  • V6
  • 2WD
  • AUTOMATIC
  • 149,700 MILES
Broke camshaft, replaced with a 3.4L Pontiac Grand am engine, 1999 as well, but with A.I.R. System in heads. Only one way check valves left. So, after replacing a lot of stuff, catalytic converter, EGR, EGR line, oil pan gasket, etc. Was ready, took it out for a test drive. Family was happy, as we had this sitting around, and I decided to use it as a learning experience for the family.

So, everything went quite well, ran nicely. Went up a hill, felt and heard a pop noise. Pulled over, knocking sound. Drove it short distance home. Checked out engine, assumed rod/main bearing. Just went to troubleshoot, and it knocks at idle, less with serpentine off. Hit throttle, and over 1,000 rpm's or so, goes away. Pulled every plug wire, makes noise worse. Noticed a small liquid spray shooting from EGR line to EGR valve. Thinking heads/valves, not quite real sure.

This is a learning experience car, so not real interested in "just get rid of it" answers. I am stumped at where to troubleshoot the problem, and would like to teach my wife and kids how to disassemble/reassemble, or why it is better to try another boneyard engine.
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Sunday, November 19th, 2017 AT 9:27 AM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,355 POSTS
There should not be anything liquid coming from the EGR. That has me a bit confused. As far as the noise, check to make sure there is nothing loose such as a flywheel bolt, a starter. Also, check to make sure the flywheel is not cracked. Let me know what you find.
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Sunday, November 19th, 2017 AT 5:44 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,355 POSTS
PS: Are you able to identify what kind of fluid is coming from the EGR? Could it be from condensation?
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Sunday, November 19th, 2017 AT 5:45 PM
Tiny
OUTTALUCK
  • MEMBER
  • 5 POSTS
It is a fine spray type. Only thing I can think of is coolant, and it has lost a small amount of coolant. I can probably put a paper towel on top and absorb some to identify the fluid.

Starter and flex plate are okay, I know that much through previous repairs. Troubleshooting a little more, the noise sometimes settles down when revving engine. I will take a video of it when it is daylight to help.
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Sunday, November 19th, 2017 AT 5:51 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,355 POSTS
That would be great.
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Sunday, November 19th, 2017 AT 6:09 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,355 POSTS
After thought. Just an FYI. These engines are notorious for intake gasket problems. So what you saw may have been coolant.
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Monday, November 20th, 2017 AT 5:51 PM
Tiny
OUTTALUCK
  • MEMBER
  • 5 POSTS
Yeah, I know about the intake gasket... That was leaking and took out the camshaft bearings in the original motor. Still have the camshaft sitting on a shelf for proof that camshafts break, because no one believes me when I tell them... Anyways, I'll be posting the video of the car engine noise. Got a pretty good video of it.
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Monday, November 20th, 2017 AT 6:57 PM
Tiny
OUTTALUCK
  • MEMBER
  • 5 POSTS
Okay, so what you'll see/hear is the 3400 SFI engine out of the 99 Pontiac Grand Am at idle, with the kock. Then you'll hear us rev the engine and then it'll go away until it slows down to an idle, then it starts up louder again. Hopefully this helps explain what I'm hearing/seeing. But, I'm guessing the prognosis is not good.

From what I've gathered, piston slap is a common problem with these years of cars on GM and Ford, which this fits in to. But. The knock stays with the engine warmed up. When I put a stethoscope on it, I can hear that throughout the entire engine, accessories included, but nothing that stands out particularly to point to where it's coming from. It's actually louder outside the engine than when I search for it with a mechanic stethoscope
Video (Click to make bigger)
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Monday, November 20th, 2017 AT 7:08 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,355 POSTS
Do me a favor. I believe the harmonic balancer is mounted on rubber and then steel again where it bolts on. Check it. I had an olds sound like that and it was the harmonic balancer's rubber mount which was shot and causing the noise. Let me know and I'll keep my fingers crossed that is the problem. Otherwise, it does sound like a bearing knock.

And yes, that sounds bad!
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Tuesday, November 21st, 2017 AT 8:07 PM
Tiny
OUTTALUCK
  • MEMBER
  • 5 POSTS
Okay, will do tomorrow. If that decided to go, would/could that rubber pop out with an audible noise while driving and cause that? The noise I heard when it started began with a noise that I thought I ran over plastic debris on road at first.
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Tuesday, November 21st, 2017 AT 8:12 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,288 POSTS
Thanks for the video! Yep it sounds like the balancer alright, with the engine off see if you can move the belt one way or the other?

Here is a guide to give you an idea of what you are in for when doing the job.

https://www.2carpros.com/articles/how-a-harmonic-balancer-works

Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken
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Friday, November 24th, 2017 AT 6:37 PM

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