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91 C2 Hollow Ringing Sound in Engine Bay

 
Old 01-02-2006, 01:43 AM
  #16  
CraigC
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Default Ringing noise

Mark,
Thanks for the quick reply, I have tommorrow off, so this will give me something to do.
Thanks
Craig
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Old 01-02-2006, 11:55 AM
  #17  
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This happened when I replaced a part of my exhaust. It was the exhaust mount on the bypass pipe in the very rear. When away once I moved it a round a little and tightened it up.
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Old 01-02-2006, 08:39 PM
  #18  
red911c2
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CraigC,

When are we going to see pictures (in a new thread) of your "new to you" 964???

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Old 01-02-2006, 11:20 PM
  #19  
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Hi Chobe22,

Welcome !

I have the same problem and I tend to agree with Adrian, it is in my opinion, definitely the fan bearing!

E Chan
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Old 01-03-2006, 12:59 AM
  #20  
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I took the belts and pulleys off and the car still makes the ringing noise when running although it doesnt seem as loud. The shaft spun smoothly and both bearings feel smooth when rotated by hand. The fan does not contact the fan shroud when spun by hand or after I put it back together and started it up. I painted the fan shroud black inside where it appeared there had been contact in the past. If it touches again it will scrape the paint off and I will know it has just happened. I can move the shaft a zillenth of an inch up and down, is that to much? is there supposed to be zero movement? I think there is a good chance the ringing may be in the exhaust, or possibly I have the fan-alternator ringing and the exhaust also ringing. I looked through the records that came with the car and it appears a shop reinstalled the fan shroud at some time but it makes no mention of alternator or fan bearing replacement.

Im glad I did this, as it gave me a chance to check out my tool kit that came with the car. None of the tools I needed to change the belt were in it, and if they had been I wouldnt have been able to change a belt by the side of the road because the same guy put on the fan nut that installed my transmission drain & fill bolts! It must have been torqued to about 300 ft lbs.
Any comments on the acceptable amount of play in the shaft is welcome.

Terry, Your avitar is my new to me 964 and your old car. I will try to post some pics although you might have better luck posting pics than me.
Thanks,
Craig
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Old 09-25-2013, 03:52 PM
  #21  
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old thread new bump -

I have this same noise - I am replacing my alternator this week - but I don't think my noise is the alternator - I think its more coming from the exhaust - but it's definately wierd - and seems to be worse if I am cruising slowly at 2500 rpm on a downtown street, sounds like a couple steel ***** in a can....hollow knocking type thing....anyone familiar with this noise?
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Old 09-25-2013, 04:44 PM
  #22  
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My first guess would be cat heat shield.
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Old 09-27-2013, 07:11 PM
  #23  
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I replaced my alternator yesterday - and MOST of the hollow clanging sound is gone - but some still remains..so maybe it was a few things together making the noise -the alternator bearing was definitely toast....so now not only do I have that bearing out of the way - the alternator was only making a portion of the power it was supposed to put out - and now the car is a rocket...which is nice....

on to the install of my cup pipe, and to look into clanging heats shields and such - and maybe come across the root of the other noise...
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Old 06-20-2015, 11:15 AM
  #24  
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Resurrecting an old thread. This hollow marbles in a tin can noise is still present. A lot of other guys have experienced this. It's not the alternator. It might be heat shields, but when the motor is idling, you'd think the noise would be worse due to more vibration, and it's less noise, not more...

It's killing me. I get these ideas in my head like rod knock, but then the motor sounds fine and the noise is not present in the motor, it seems...so can't be. And then I think, maybe it's the planetary gear...and God only knows. Then maybe I think could it be the flaps inside the heater blowers that blow heat behind the wheels????? Is that possible?

Has anyone experienced this noise and fixed it?
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Old 06-20-2015, 12:25 PM
  #25  
JasonAndreas
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Originally Posted by Goughary View Post
This hollow marbles in a tin can noise is still present. A lot of other guys have experienced this. It's not the alternator. It might be heat shields, but when the motor is idling, you'd think the noise would be worse due to more vibration, and it's less noise, not more...
Have you tried locating the sound with a
mechanic's stethoscope mechanic's stethoscope
? The 12-18" or so hollow tube on the end really helps to pin point the source and they only cost $15.
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Old 06-20-2015, 12:47 PM
  #26  
Greg_V
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Default 91 C2 Hollow Ringing Sound in Engine Bay

A broomstick (or other short wood dowel of similar size) held to your ear / touching various parts of the engine also works in a pinch if you don't have a mechanics stethoscope.
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Old 06-20-2015, 01:28 PM
  #27  
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Originally Posted by Greg_V View Post
A broomstick (or other short wood dowel of similar size) held to your ear / touching various parts of the engine also works in a pinch if you don't have a mechanics stethoscope.
Marbles in a can is a typical description of a worn chain, guide or collapsed tensioner.
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Old 06-20-2015, 03:18 PM
  #28  
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Originally Posted by Goughary View Post
Resurrecting an old thread. This hollow marbles in a tin can noise is still present. A lot of other guys have experienced this. It's not the alternator. It might be heat shields, but when the motor is idling, you'd think the noise would be worse due to more vibration, and it's less noise, not more...

It's killing me. I get these ideas in my head like rod knock, but then the motor sounds fine and the noise is not present in the motor, it seems...so can't be. And then I think, maybe it's the planetary gear...and God only knows. Then maybe I think could it be the flaps inside the heater blowers that blow heat behind the wheels????? Is that possible?

Has anyone experienced this noise and fixed it?
As unlikely as it sounds I've had this thread open in my phone for a long time. Initially I thought something really bad is happening, until recently I met another new 964 owner, who also had rebuild, and when he started his car the same ringing was there. Based on previous posts on here I thought it would be the fan bearing, but now I'm not so sure.

Its loudest at start up and fades a bit once the car warms up, but even then its very faint and can be heard if driving by barrier so the sound shoots off it.

Originally Posted by J richard View Post
Marbles in a can is a typical description of a worn chain, guide or collapsed tensioner.
I have some semi-frequent chain drag/rattle on start up, but I've heard this is on the normal side until tensioners pick up the slack.
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Old 06-20-2015, 11:34 PM
  #29  
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Originally Posted by J richard View Post
Marbles in a can is a typical description of a worn chain, guide or collapsed tensioner.
I thought maybe those as well...but they were all replaced a few weeks ago. So no dice there...I wish one of the many things I had to do anyway would have resolved this.

Oh and here is another tidbit. The frequency of the marbles in the can doesn't change with the rpm...but it does go away and return it seems. This is why I thought maybe chain guides. But now all those are new. So I'm lost.

Who else has the sound?
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Old 06-21-2015, 01:22 AM
  #30  
J richard
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Any chance you can get it on vid?
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