Cracked Head?
Thread Starter
Drifting
Joined: May 2001
Posts: 2,224
Likes: 24
From: Indiana
Cracked Head?
I posted this in another thread but it may have got lost. This involves the 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 responders 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."
This has got me worried a bit. Anyone have any experience with a cracked head? If the head was cracked would there be other symptoms? Anyone have any experience or comments?
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 responders 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."
This has got me worried a bit. Anyone have any experience with a cracked head? If the head was cracked would there be other symptoms? Anyone have any experience or comments?
