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S80 '06-'16 / V70 & XC70 '07-'16 General Forum for the P3-platform S80 and 70-series models |
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Noise at cold startViews : 2810 Replies : 26Users Viewing This Thread : |
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Nov 10th, 2018, 09:27 | #21 |
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Thank you for your replies.
The timing and serpentine belts with pulleys and tensioners were replaced less than a year ago. Yes, the noise changes when I rev the engine. The rattle noise is heard 20-30 seconds after a cold start (idling). Yesterday, after hours of troubleshooting and testing, I discovered the source of noise coming from somewhere underneath the car from the catalytic converter area. Could it be a bad catalytic converter? What could generate this rattle noise in the catalytic converter? Here is the sound file again: https://youtu.be/aX1jngcvKN0 |
Nov 10th, 2018, 11:02 | #22 |
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There is an experience on another make of car which seems to offer a route to diagnosis. On certain 2.0 Peugeot engines there is a mild steel welded construction in the inside of the exhaust manifold. With ageing the weld corrodes and the steel construction vibrates inside the manifold in the gas flow at specific harmonics. Before anyone knew about this it was a nightmare problem for owners but once the fault was revealed it was the first place to look when this sort of fault arose. Since the location now seems to be inside the exhaust system, it seems that removal of the exhaust and examination for loose components would be a reasonable strategy.
I read back through this post looking for details of to which car this refers but most of the thread is taken up with irrelevant horn locking over Bendix drives! The interesting thing about this fault is that is seems to be temperature related and so expansion in the exhaust system may well be at the bottom of this problem.
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Nov 10th, 2018, 12:14 | #23 |
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Thank you Tatsfield. The car model in question is a Volvo V70III 2.5T, MY2008 with engine B5254T6.
The car has high idle speed for about 30 seconds after cold start in order to knock the catalyctic converter up, and it is during this first 30 seconds the noise appears and then eventually fades. If I drive for some time and then park the car for half an hour or so the noise appears but less noisy and for a shorter time (five seconds or even less). I believe you are right, Tatsfield, when you suspect the issue to be temperature related. Something is most likely expanding in the exhaust system when it heats up and the metallic rattle noise stops. |
Nov 10th, 2018, 17:14 | #24 |
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Catalytic converters can fall apart internally and rattle, also heat shields can get loose and rattle. The heat from the exhaust can change the sound.
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Nov 11th, 2018, 14:26 | #25 |
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I have been googling this metallic grinding noise this weekend and eventually I came across this youtube video that is dealing with the exact same grinding noise: https://www.youtube.com/watch?v=KZnpKwO0yUE
According to the comments to this video loose manifold bolts was the reason for the grinding noise. What do you say? Does it sound likely and plausible? |
Nov 12th, 2018, 03:16 | #26 |
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Nov 12th, 2018, 11:02 | #27 |
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No but the dispute did tend to clutter the thread in regard to the fault. What was said about Bendix drives was all acceptable information, just extraneous to the needs of the OP and his fault finding exercise. And now I'm contributing to the clutter! Sorry
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