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Old 08-11-2015, 09:38 PM   #1
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Exclamation Alarming engine noise

My 1995 Olds Ciera with the 3100 FWD configuration recently started making an alarming engine noise that can be heard when the vehicle is sitting at specific angles. The noise presents itself while braking hard, reversing hard, or parking facing downhill.

Any ideas? I took a video of the issue on my iPhone.

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Old 08-11-2015, 09:45 PM   #2
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That is alarming!

I would start looking for exhaust manifold leaks at the heads.
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Old 08-11-2015, 10:23 PM   #3
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That is alarming!

I would start looking for exhaust manifold leaks at the heads.
When I hear that noise, "exhaust" isn't exactly the first thing to come to mind. Care to explain this?
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Old 08-11-2015, 10:52 PM   #4
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When I hear that noise, "exhaust" isn't exactly the first thing to come to mind. Care to explain this?
Because it only does it when the engine is trying to torque backwards. Usually engine noises don't tend to go away in those scenarios. I am also thinking that the tension of the exhaust in relationship to the rocking engine causes it to pull the manifolds one way or the other. It also sounds like it could be a release of compression, but most other scenarios would have the noise happening all the time. You would be looking for a leak before the exhaust collects, so between the heads and the down pipe. Sounds like it may even be more than one cylinder, unless that was idling really high.

Another possibility is one of the engine pulleys is hitting something it shouldn't, but you should be able to spot that, and is usually caused by excessive movement, like from a bad mount.
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Old 08-11-2015, 11:14 PM   #5
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Because it only does it when the engine is trying to torque backwards. Usually engine noises don't tend to go away in those scenarios. I am also thinking that the tension of the exhaust in relationship to the rocking engine causes it to pull the manifolds one way or the other. It also sounds like it could be a release of compression, but most other scenarios would have the noise happening all the time. You would be looking for a leak before the exhaust collects, so between the heads and the down pipe. Sounds like it may even be more than one cylinder, unless that was idling really high.

Another possibility is one of the engine pulleys is hitting something it shouldn't, but you should be able to spot that, and is usually caused by excessive movement, like from a bad mount.
So your theory, then, is that certain types of motion are moving the exhaust manifold away from the engine in such a way that it loses compression. This compression loss is what I'm hearing.

Some more exhaust related info: when the engine is cold, you can hear the exhaust quite loudly. It seems to be leaking. When the engine heats up, the sound goes away and it sounds quite good. Do you think I may need to check out my manifold?

Thanks for your help, by the way. I'm at a loss because I'm more handy with computers than I am with cars.
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Old 08-12-2015, 12:42 AM   #6
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I don't think it'* losing compression, it'* just allowing the blast of exhaust gasses to escape from the manifold, near the source, instead of directing it through the exhaust system like it should.

Smoke is a great way to find exhaust leaks usually, if a visual inspection doesn't turn anything up immediately apparent.
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