Crown

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    Aug 23, 2009 8:03:21 PM

    Greentree
    Co-Pilot
    Greentree
    Loc: Texas, USA , United States
    Posts: 151, Gallery
    Registered on: Jul 1, 2007

    What's this noise?

    I have developed a brief gear clash sound that occurs just after initial start up of my GT3.  It happens only when the engine is stone cold and has not been run for at least ten to twelve hours.

    It doesn't happen all the time, just occasionally.  That's a problem since it can't be reproduced reliably.  It never would occur when it was at the dealer.  Finally I decided to try and catch it on video.

    After playing hide and seek with the gremlin for nearly a week I finally succeeded in capturing the clash on video.  You'll hear occur about one second after the engine starts.

    It occurs with the clutch completely depressed.  It doesn't matter if the air conditioning is on or off.  I think what's happening is the starter gear pulls out of the flywheel ring gear, but as the starter motor coasts to a halt, its gear creeps back and "touches" the ring gear.  The clash immediately throws the starter gear back to its at-rest position.  Once the engine has warmed up, even a little, it doesn't happen anymore.  On the other hand, maybe I'm being fooled and it has nothing to do with the starter at all.

    The starter has been replaced, but it's still there.  Has anybody out there had this problem?  What is it?Smiley

    dscf0057.avi


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    2008 GT3

     

    Aug 23, 2009 10:16:09 PM

    fritz
    Rennteam VIP
    fritz
    Loc: BaWü , Germany
    Posts: 10248, Gallery
    Registered on: Jul 23, 2003
    Reply to: Greentree

    Re: What's this noise?

    Greentree:

    I have developed a brief gear clash sound that occurs just after initial start up of my GT3.  It happens only when the engine is stone cold and has not been run for at least ten to twelve hours.

    It doesn't happen all the time, just occasionally.  That's a problem since it can't be reproduced reliably.  It never would occur when it was at the dealer.  Finally I decided to try and catch it on video.

    After playing hide and seek with the gremlin for nearly a week I finally succeeded in capturing the clash on video.  You'll hear occur about one second after the engine starts.

    It occurs with the clutch completely depressed.  It doesn't matter if the air conditioning is on or off.  I think what's happening is the starter gear pulls out of the flywheel ring gear, but as the starter motor coasts to a halt, its gear creeps back and "touches" the ring gear.  The clash immediately throws the starter gear back to its at-rest position.  Once the engine has warmed up, even a little, it doesn't happen anymore.  On the other hand, maybe I'm being fooled and it has nothing to do with the starter at all.

    The starter has been replaced, but it's still there.  Has anybody out there had this problem?  What is it?Smiley 

    Could it be coming from the VarioCam, caused by the build up of oil pressure in the system after startup from cold? Smiley


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    fritz

    Aug 24, 2009 1:47:31 AM

    Greentree
    Co-Pilot
    Greentree
    Loc: Texas, USA , United States
    Posts: 151, Gallery
    Registered on: Jul 1, 2007
    Reply to: fritz

    Re: What's this noise?

    Hmm, well, that's a possibility.  In other words, it's not gear clash at all, but the cavitation of high pressure oil.  I'll mention it to the service manager.  Thanks for the tip.

    I really miss working on cars myself.  However the Porsche requires a lot of specialized equipment, and manuals for a late model car are just impossible for the average Joe to get  --even if you are willing to pay the price (which I'm not).  Yet, when something goes wrong, I've just got to figure out what it is, even if it's not my problem.  It's like solving a puzzle.


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    2008 GT3

     

    Aug 24, 2009 2:04:58 AM

    Trundle_GT3
    Veteran
    Trundle_GT3
    Loc: CA, USA
    Posts: 1016, Gallery
    Registered on: Jun 30, 2003
    Reply to: Greentree

    Re: What's this noise?

     It's not uncommon, mine will do it on occasion.

    Others I know have heard it as well.

    Even the previous version would do it as well.

    SpeedGeek posted this on another forum: "I've never found a pattern to when it smokes. It's the occasional machine-gun rattle that freaks me out more than the smoke."

     

    You are not alone


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    997 GT3 Guards Red

    Aug 25, 2009 5:49:48 PM

    Greentree
    Co-Pilot
    Greentree
    Loc: Texas, USA , United States
    Posts: 151, Gallery
    Registered on: Jul 1, 2007
    Reply to: Trundle_GT3

    Re: What's this noise?

    The dealer couldn't reproduce it and had to rely on my video hear it.  They inspected the teeth on the ring gear and saw no damage.  After I brought it home the second time, I've haven't heard it.  Maybe there is something about the inspection procedure that fixes the problem as a side effect.

    Yeah, there is no pattern to the smoke.   I got some this morning matter of fact.  I'm willing to overlook that since we've all seen it many times before.


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    2008 GT3

     

    Sep 28, 2009 2:04:27 AM

    stuski1
    Newbie
    stuski1
    Loc: Plattsburgh , United States
    Posts: 21, Gallery
    Registered on: Feb 4, 2007
    Reply to: Greentree

    Re: What's this noise?

    I hear it too, somewhere I read it is normal, something to do with limited slip, Since New.

    But I have  a new noise, sounds like grinding marbles in front end when slowing down, car in gear or not.

    When I went to dealer to duplicate it, it wasn't there, it figures.Never tracked car.

    I drove from Montreal to NY border following others doing over 100 mph.

    I got 2 yrs left on warranty, 8,800 miles. Had rear tires replaced, fronts not, since then

    is when I developed new problem/noise.

     

    Sep 30, 2009 2:56:56 AM

    Greentree
    Co-Pilot
    Greentree
    Loc: Texas, USA , United States
    Posts: 151, Gallery
    Registered on: Jul 1, 2007
    Reply to: stuski1

    Re: What's this noise?

    The dealer replaced the starter with brand new.  At first I thought the noise went away.  But, no, the noise is still there.  I guess we can eliminate the starter being the problem.

    I notice when I first start up (after not running for at least 12 hours) there is a brief moment before the oil pressure needle goes to 5 bar.  If that brief moment is too long, I hear the noise.  If that moment is short, (when the engine has been stopped for just a few hours),  I don't hear the noise.  Maybe the noise has something to do with oil flooding the oil galleys pushing a slug of air ahead of it.

    I guess I'll have to wait until something breaks in order to know for sure what is it.  It's a Porsche Certified car.  Hopefully if something should break it'll still be under warranty.

    The front will sound like grinding marbles if you are pressing the brake pedal very firmly.  It's the anti-skid control kicking in.  You shouldn't hear it with normal braking though.


    --

    2008 GT3

     

    Sep 30, 2009 3:26:38 PM

    MarekN
    Pilot
    MarekN
    Loc: Czech Republic
    Posts: 409, Gallery
    Registered on: Jun 7, 2006
    Reply to: Greentree

    Re: What's this noise?

    Myself and other people on both boards say don´t worry about it. Other people have it as well. Mine does it also sometimes, but I drive the car only once a week (poor me) and it doesn´t do it on every occasion. It is definitely a mechanical grinding noise in mine, no air being pushed,but metal to metal contact. I figured it could be the hydraulic valve tappets a split second before oil gets in there.

    What do you say to that?

    As for the time and period of the event, it is identical to yours. On another note, my car has 28,000 km and is perfectly healthy with 0,2 liters of oil consumption per 10,000 km. Smoke on start up is a normal event to me. Sometimes less, sometimes more.

     

     

    Oct 1, 2009 12:48:48 PM

    Greentree
    Co-Pilot
    Greentree
    Loc: Texas, USA , United States
    Posts: 151, Gallery
    Registered on: Jul 1, 2007
    Reply to: MarekN

    Re: What's this noise?

    Yeah, one just needs to get accustomed to getting a little smoke every once in awhile.

    Earlier in the post Fritz suggested it was one of the VarioCam mechanisms chattering.  I think there are little metal vanes inside that gizmo.  Maybe they rattle as air passes through them.  It's the "metal to metal" noise that bothers me.  That can't be good.  But the engine is very stout.  I guess these little noises just doesn't bother it.

    I'm going to experiment this morning.  I'll turn over the engine (but not allow it to start) a couple of times.  Then I"ll start it and see what happens.  The idea is to get some oil up into the galleys before the engine spins up.


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    2008 GT3

     

    Oct 1, 2009 3:59:24 PM

    MarekN
    Pilot
    MarekN
    Loc: Czech Republic
    Posts: 409, Gallery
    Registered on: Jun 7, 2006
    Reply to: Greentree

    Re: What's this noise?

    I had a similar thought about unplugging the electrics and just letting it spin on the starter motor for five six seconds and then putting the leads back on and then starting it to have the same effect as you say, but when you lift the hood and all you get is an air filter and some block, you quickly pop it back in place and just forget about it.

    It´s like you say, on these modern machines, you can hardly do anything at all beyond an oil change at home.

     
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