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Cold Start Knocking Noise GTP

12-27-2007, 11:26 PM
I have a 2005 GTP with 69000 miles that developed a knocking noise when weather turned cold. After the car warms up the noise goes away. It doesn't sound like typical valve clatter. It sounds almost like a plastic fan blade hitting something metal. It's not the cooling fan however, and it does track the rpm. It's hard to determine where sound is coming from. You can here it from the front center of engine. Hard to say.

I thought maybe it was oil related and changed oil. Using Mobile 1 5w30 with the mobile extended oil filter. I also threw in a quart of Lucas Synthetic oil stabilizer to see if that would help.

Any ideas? I have been car shopping as one idea but ????? OOOUUUCCCHHH.

Mike B

12-28-2007, 01:21 AM
piston slap possible here. If it is, there really is nothing that can be done to correct it. Its just one if those things.

Are you filling up with premium 91 octane or better?

12-28-2007, 07:36 AM
piston slap possible here. If it is, there really is nothing that can be done to correct it. Its just one if those things.

Are you filling up with premium 91 octane or better?

I'm using 93 octane.

Mike B

12-28-2007, 09:08 AM
Although it is possible it is highly unusual for a L32 SIII 3800 engine to have piston slap. Piston slap is usually there regardless of the weather. It will be there in the warmer months but disappears after about 1 minute or so of engine warmup.

Has this noise been pinpointed? Is it really a knocking sound or ticking sound? Maybe it is drive belt noise or supercharger related. Check your pulleys (all idler and tensioner) and disconnect the SC drive belt if the sound originates from there.

brian 1
12-28-2007, 05:17 PM
you might want to try this,had some gp's like this.check the dust cover that goes at the bottom of the transmission.found a bulletin for this problem.not saying it will fix the problem,but i've fixed alot of them with this problem.Subject:Rattling, Ticking or Scraping Noise from Engine Compartment (Inspect Transmission Rear Dust Cover) #05-06-01-028 - (09/16/2005)

Models:2005 Buick Park Avenue
2005-2006 Buick Allure (Canada Only), LaCrosse, LeSabre
2006 Buick Lucerne
2005 Chevrolet Impala, Monte Carlo
2005 Pontiac Bonneville
2005-2006 Pontiac Grand Prix, Grand Prix GTP
with 3800 Series II or Series III 3.8L V6 Engine (VINs K, 1, 2, 4 -- RPOs L36, L67, L26, L32)

<A href="">Condition

Some customers may comment on a rattling, ticking or scraping noise coming from the engine compartment.
<A href="">Cause

This condition may be caused by the transmission rear (flywheel/flexplate) dust cover being installed incorrectly, resulting in the cover contacting the flexplate.
<A href="">Correction

<A href="">Figure 1 - Transmission Dust Covers (
(1)Rear Transmission Dust Cover(2)Front Transmission Dust Cover(3)Guide Tab<A href="">Figure 2 - Correct Installation of Transmission Dust Covers (
(1)Rear Transmission Dust Cover Alignment Feature (Refer to Step 6)(2)Front Transmission Dust Cover Notch locates above the Rear Transmission Dust Cover Alignment Feature (Refer to Step 6)(3)Front Transmission Dust Cover Guide Tab tucks behind the Rear Transmission Dust Cover
Inspection of Rear Transmission (Flexplate) Dust Cover
<A href="">Figure 3 (
Important: The rear dust cover has a designed-in bow. Refer to the shaded area (3) of the illustration above. Do not confuse this designed-in bow as a warp in the cover.
<LI type=1>Remove the front and rear transmission dust covers. Refer to Figure 1. <LI type=1>Start the engine. If the noise is present, it is not being caused by the transmission dust covers. Continue diagnosis until the source of the noise is found. Then proceed to Step 5 for correct installation of the covers.
If the noise is not present, continue to the next step.
<LI type=1>Inspect the rear cover in the area shown (1) for signs of it having contacted the flexplate. Refer to Figure 3. <LI type=1>If there are signs of contact (refer to Figure 3), use a sharp knife to cut away some of the plastic as shown by the dotted line (2). <LI type=1>Install the front dust cover (2). Refer to Figure 1.
After the front dust cover is installed (refer to Figure 2), position the rear cover so that the tab (3) on the front cover is behind the rear cover, as shown. When properly positioned, the alignment features (1 and 2) will be positioned as shown with the tab (3) hidden from view.

12-28-2007, 11:53 PM
Thanks For giving me some things to try. I'll post is I do or don't find something.

Mike B

12-31-2007, 02:35 PM
Thanks a million for your help. I'm glad there are people like you that come to these forums and help people like me out.

The problem was the fly wheel cover. I trimmed it and the problem was solved. The noise was coming from underneath but you had to be under the car to here the source. When you lift the hood the sound resonated through to the front center and sounded like it was coming from the center of the engine and exhaust. It truley sounded like a major problem and not the minor fix that it was.

Again thanks!! and Happy New Year!!

Mike B

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