Funny noise, or normal for 993?
02-04-2002, 05:05 PM
#1
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Funny noise, or normal for 993?
Hi Folks,
Again, I've searched the archives but can't find anything related to this, so my apologies if it's a common thread. I used "funny noise flutter rattle clatter" and matched any, but found nothing relative.
When driving the 993 with the windows down I notice that it makes a bit of a "flutter" noise as the engine settles to idle. It only last for a couple of seconds and it's not awful, but it sounds a bit like the "valve clatter" that I've heard on cars before.
I've only recently been driving the car with the windows down due to the weather, so I don't know if this was present when I bought it or not. I had the car checked at the local Porsche dealer last week and the mechanic said that it was in excellent condition. He has a reputation for being a thorough, detail-oriented guy, so I'd think that he would have commented if there was a problem.
Should I worry, or is this just one of the noises that a 993 makes? If it is abnormal, do I need to get it into the shop ASAP, or what?
Thanks!
Again, I've searched the archives but can't find anything related to this, so my apologies if it's a common thread. I used "funny noise flutter rattle clatter" and matched any, but found nothing relative.
When driving the 993 with the windows down I notice that it makes a bit of a "flutter" noise as the engine settles to idle. It only last for a couple of seconds and it's not awful, but it sounds a bit like the "valve clatter" that I've heard on cars before.
I've only recently been driving the car with the windows down due to the weather, so I don't know if this was present when I bought it or not. I had the car checked at the local Porsche dealer last week and the mechanic said that it was in excellent condition. He has a reputation for being a thorough, detail-oriented guy, so I'd think that he would have commented if there was a problem.
Should I worry, or is this just one of the noises that a 993 makes? If it is abnormal, do I need to get it into the shop ASAP, or what?
Thanks!
02-04-2002, 07:24 PM
#3
Skip,
Can you replicate the sound by revving the engine and letting it settle to idle each time? Does the sound only happen right before settling? Does it sort of sound like a loose exhaust? If so, I have a similar noise and so far the best or most logical explanation given to me by a couple of experienced mechanics(other than something loose on the exhaust system) has been the that material in the catalytic converter become loose and makes the “flutter or sort of rattling noise”. I am still investigating though. I would be interested in what you have found out.
Can you replicate the sound by revving the engine and letting it settle to idle each time? Does the sound only happen right before settling? Does it sort of sound like a loose exhaust? If so, I have a similar noise and so far the best or most logical explanation given to me by a couple of experienced mechanics(other than something loose on the exhaust system) has been the that material in the catalytic converter become loose and makes the “flutter or sort of rattling noise”. I am still investigating though. I would be interested in what you have found out.
02-04-2002, 07:51 PM
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Skip, I think DJ is right and it's the rear spoiler lowering. There's an easy way to find out. Put the spoiler up manually so it doesn't lower when you come to a stop and see if the flutter goes away.
I had the same concern and it was the spoiler.
Buck
I had the same concern and it was the spoiler.
Buck
02-04-2002, 08:19 PM
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All,
Thanks for the tips, I'm going to check things out a bit more tonight. I don't believe that it's the spoiler lowering, in fact mine is very quiet with only a mild hum if I listen closely. The noise is also present if I am parked and rev the motor a bit then run around back to listen. It does sound a bit like a loose exahaust, so I'm going to check the bolts for that.
I was going to look into one of the alternate exhaust systems that I read about here frequently, so my guess is that this is one possible "fix". Not that I'd do this just to get rid of the sound, mind you, but it should go away if I replace it, right?
As for recommendations on a replacement exhaust system, RSR seems to be the favorite...
Cheers!
Thanks for the tips, I'm going to check things out a bit more tonight. I don't believe that it's the spoiler lowering, in fact mine is very quiet with only a mild hum if I listen closely. The noise is also present if I am parked and rev the motor a bit then run around back to listen. It does sound a bit like a loose exahaust, so I'm going to check the bolts for that.
I was going to look into one of the alternate exhaust systems that I read about here frequently, so my guess is that this is one possible "fix". Not that I'd do this just to get rid of the sound, mind you, but it should go away if I replace it, right?
As for recommendations on a replacement exhaust system, RSR seems to be the favorite...
Cheers!
02-04-2002, 10:41 PM
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I know I am probably completely off base here
and I have don't have much technical ability but I thought it couldn't hurt to raise another possibility.
Is it possible that it could be a belt that needs to be replaced.
My thinking is, when my car started cold it made a weird noise until it warmed up. I changed my belt and problem solved. Now I know your problem is different but it would seem to me that a belt at high rev's may be less taught then a belt at low revs. So maybe when your car comes down in revs, the belt becomes a little loose and makes some noise.
--hope this wasn't a really stupid suggestion.
and I have don't have much technical ability but I thought it couldn't hurt to raise another possibility.
Is it possible that it could be a belt that needs to be replaced.
My thinking is, when my car started cold it made a weird noise until it warmed up. I changed my belt and problem solved. Now I know your problem is different but it would seem to me that a belt at high rev's may be less taught then a belt at low revs. So maybe when your car comes down in revs, the belt becomes a little loose and makes some noise.
--hope this wasn't a really stupid suggestion.
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02-05-2002, 10:47 AM
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From the description, it sounds like normal 911 noise. My '78 SC did it and my '96 Carrera does it but it a slightly different fashion. Partly fan noise and partly muffler baffling.
Regards,
Don
Regards,
Don
04-10-2002, 11:36 AM
#9
Has anyone completely diagnosed and/or fixed this “flutter,” “rattle” or whatever you want to call the sound some peoples 993's are making on rev-down? I saw the following posted on the 911 list a couple of days ago:
“I also had a bizarre (rare but not unheard-of) cracked head issue with mine - symptoms sounded like gravel rattling in the muffler - required an entire top end about $5k, which was covered by my (extended) warranty.”
I then emailed the author and inquired for more specifics. Here is the correspondence I sent and received (with the responder’s name, email, etc. cut”):
My email:
I read your post from yesterday with great interest regarding your 993 and a cracked head. You described the symptoms as a gravel sound in the muffler. Was this a consent sound? I ask this because I have an interesting sound that I am trying to decipher. It sounds like some thing is loose on the exhaust system or maybe “a gravel in the exhaust system” type of sound. It really can only be heard when the revs approach idle. What I mean by this, is that when the car is parked you can rev the engine a little and as the revs settle down to about the idle speed there is a “rattling” sound. Then it quiets. I have checked the exhaust and can find nothing loose. My mechanic suggested that it could be the catalytic converter material starting to come loose within the cat. Can you suggest what else was a sign of your cracked head experience?
Response was:
"This *sounds* like the same symptoms I experienced with my car. There were no other symptoms, the car seemed to run fine, just this rattling in the rev-down scenario you suggest.
The only way to verify that I know of is to pull the exhaust and see exactly what is rattling around in there. If it's chunks of black ceramic, you're probably looking at pieces of a ceramic collar insert located around the exhaust valve seat. The bad news is, you can't tell which head(s) are involved without getting pretty far into a top end teardown.
I was most concerned that some kind of overheat situation had caused this, and there might be other collateral damage, but the tech assured me everything was normal, and I got to look things over when the engine was out and in pieces, and saw nothing untoward.
It's certainly possible you've got a disintegrating cat, but that's a pretty expensive piece to replace on speculation. I'd try to get the debris out to see if you can identify it before spending any real money.
If your car isn't too long in the tooth (or even if it is) and you do have a head coming apart, I'd explore trying to get Porsche to cover it, this is clearly a defect."
Anyone have any experience or comments? This has got me worried a bit.
“I also had a bizarre (rare but not unheard-of) cracked head issue with mine - symptoms sounded like gravel rattling in the muffler - required an entire top end about $5k, which was covered by my (extended) warranty.”
I then emailed the author and inquired for more specifics. Here is the correspondence I sent and received (with the responder’s name, email, etc. cut”):
My email:
I read your post from yesterday with great interest regarding your 993 and a cracked head. You described the symptoms as a gravel sound in the muffler. Was this a consent sound? I ask this because I have an interesting sound that I am trying to decipher. It sounds like some thing is loose on the exhaust system or maybe “a gravel in the exhaust system” type of sound. It really can only be heard when the revs approach idle. What I mean by this, is that when the car is parked you can rev the engine a little and as the revs settle down to about the idle speed there is a “rattling” sound. Then it quiets. I have checked the exhaust and can find nothing loose. My mechanic suggested that it could be the catalytic converter material starting to come loose within the cat. Can you suggest what else was a sign of your cracked head experience?
Response was:
"This *sounds* like the same symptoms I experienced with my car. There were no other symptoms, the car seemed to run fine, just this rattling in the rev-down scenario you suggest.
The only way to verify that I know of is to pull the exhaust and see exactly what is rattling around in there. If it's chunks of black ceramic, you're probably looking at pieces of a ceramic collar insert located around the exhaust valve seat. The bad news is, you can't tell which head(s) are involved without getting pretty far into a top end teardown.
I was most concerned that some kind of overheat situation had caused this, and there might be other collateral damage, but the tech assured me everything was normal, and I got to look things over when the engine was out and in pieces, and saw nothing untoward.
It's certainly possible you've got a disintegrating cat, but that's a pretty expensive piece to replace on speculation. I'd try to get the debris out to see if you can identify it before spending any real money.
If your car isn't too long in the tooth (or even if it is) and you do have a head coming apart, I'd explore trying to get Porsche to cover it, this is clearly a defect."
Anyone have any experience or comments? This has got me worried a bit.
04-10-2002, 01:44 PM
#10
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Skip,
Mine does make just a bit of the rattle...it's very subtle, at not really noticable on the road unless there are only a few cars out; otherwise, there's too much ambient noise to really hear it.
I confirmed it was one of the exhaust tips by having someone rev the engine and let it drop to idle while I poked around in the exhaust tips with a long screwdriver. I found that by pressing on a metal "wall" within my left tip, the rattle stopped. Perhaps this could ease some you your concerns.
Edward
Mine does make just a bit of the rattle...it's very subtle, at not really noticable on the road unless there are only a few cars out; otherwise, there's too much ambient noise to really hear it.
I confirmed it was one of the exhaust tips by having someone rev the engine and let it drop to idle while I poked around in the exhaust tips with a long screwdriver. I found that by pressing on a metal "wall" within my left tip, the rattle stopped. Perhaps this could ease some you your concerns.
Edward