Ok. I have delayed posting this because it seems almost impossible to describe, and since I cant find a way to record the sound - I know it will be hard to diagnose.

I have a 2005 GTO (LS2). When it sits overnight, or even for a workday in the lot, it makes a pretty nasty sound during cold start. For the first 2 or 3 seconds I guess, it sounds like a rough grind type of noise. Now I know "grind" may be a bit harsh, but all I can really say is that its not valve clatter or anything like that. I have changed my oil more often than required, and use mobil 1 filter. No leaks, oil levels good, using Mobil 1 so I think I have my bases covered.

Anyone know what this could be. After about a minute and its warm, there is no evidence of the sound. It seems to be very nasty for about 3 seconds, and then tapers off for about the next 15, getting fainter and fainter.

Its not a solid grinding sound, it seems to fluctuate perhaps like "gu gu gu gu gu gu gu" or something like that, and is DEFINATELY coming from front of car, not exhaust related.

Reason I posted here, is I dont think this is a GTO only issue, and I needed any advice I could get. After its warm, I could start it all day long with NO SOUNDS at all, nice smooth starts. No change in performance while driving, no strange noises while driving, just this when its a cold start.

Thanks for anything at all guys.

Danon - -

 

My first thought when you said after startup for 3 seconds it makes a grinding noise was the starter sticking on the flywheel but .... idk what else it could be ... Keep us posted.
Good luck
p.s. doesnt the car still have a warranty ?

 

Hey try and take off the drive belts and start it sometime when your sure it will make the noise.If the noise is gone you just narrowed it down. When you do this make sure the Secondary air pump is unplugged. I have had them make noise if it is still on the car. Let me know what you find with the belt thing. Good luck!

 

Thanks for all the help, I will have to get some time tomorrow evening to try out the suggestion, I will keep you posted. If anyone else has some other ideas, that would be great...

it still has a warranty, thats the only reason Im not really really worried..

But taking it to the dealer would be a waste, since it has to sit and get cold for it to do it.

d - -

 

Can you narrow it down a little more? Is the niose coming from the drivers side or pass? from the top of the motor or the bottom? front or back......ETC.

let me know
Al

 

ok, its coming from the front, I think drivers side. I really hated posting because I know how vague this is, almost like you have to be here. I did this, this morning and the car produced no griding sound. I put the key to battery power, turned on the AC unit to high, backed off, did it twice, put the car in neutral, and then started it. Its an M6 btw...

no noise, im gonna try again this evening after work when it should produce the sound, and see what happens. Had a friend come over, he heard it, and had no clue at all.

like i said, I take it to the dealer and it will be warm, I will start it up, no noise will happen and you know what that means, wasted fuel. I have 11k on the car, and oil level/color checks out fine, just changed oil 5 weeks ago.

thanks for trying to help my guys, it really is much appreciated.

danon --

 

piston slap ???? lifter pumping up ?
didnt LS1's have this problem ?

 

I had an intermittant starting issue with my 01 WS.6 a week ago. The dealer kept her overnight and worked on her a good bit. Never found it, but I think when they put the column back togather they maybe plugged a wire in that was loose or something. They charged me nothing. I am sure they will keep your car overnight.

 

take your car in and leave it overnight. if they still dont hear anything than leave it untill they do if your that concerned with it.
we allways suggest a customer leave their vehicle when its a cold start issue to give us a better chance of hearing the noise. this would be my suggestion to you. goodluck with it.

 

I appreciate the advice....

damn I hate leaving my car at the dealer, last time I did it came back with a ding in the door, and scratch on the door handle, they had to fix/repaint it all and it tooks over a week....

i think i carry bad luck around in my trunk.

last three days it has only happened twice...i dont know whats going on, does it sometimes, doesnt others...

thanks again for the help and advice

i will think about it and try to find a really really respectable dealer in the north houston area..

danon - -