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#3390303 - 06/06/14 01:16 AM three knocks heard at idle after sitting overnight
npfd Offline


Registered: 06/05/14
Posts: 9
Loc: Canada
Hi all,

The car is a 2007 Grand Prix, with the 3800 N/A.
We bought it second hand in 2011 with about 57k kms, now it has about 102k kms.

I used to hear this a while ago, I think even the first winter when we had the car.

Let the car sit overnight, and start it and drive several minutes and at a light at idle, I'll hear three knocks from the engine bay.

Some of the work we did:
Change plugs and wires
Redid the LIM
Ran a few techron tank fuels,
Premium fuel.
Checked the heat shields, one of them is a little loose
PCV changed with new gasket, in 2011
MAF cleaned a few times
Coils checked resistance
I do have to monitor the oil level every month, sometimes need to add a little, a small cup.
After reading on forums, ran Auto RX in the winter time. from November to February.
I used to hear the knocks, but at some point hte first knock was louder then the second after were quieter. Then eventually I would stop hearing the knocks.

Currently been using PF47 Ac Delco filter, and Quaker State 5w30 oil.

It was suggested that maybe the piston crowns are dirty due to the short drives, about 2 miles to and back from work. I do try to try on the highway 20 minutes one way several times a week.

I bought MMO, and was about to put it in the crankcase, but didn't and returned it..
Afraid that it might cause more leaks... after reading a fair amount on forums etc... most favour mmo... but looking at how its a solvent I was afraid it would aggravate the Rear main leak that's been going on since we bought the car.

We usually change the oil every 4 months... or 3x a year... regular dino oil...

Should I run another dose of Auto RX, or the maintenance.. safe to use the MMO maybe a week before changing the oil?
With the job i have right now I can just about keep the operating costs of the car, as any compression test etc,,, wouldn't be done right away maybe soon...

Thank you

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#3390309 - 06/06/14 01:31 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
Marco620 Offline


Registered: 02/25/14
Posts: 207
Loc: Midwest, Rural KS
Could be a timing issue or belt/tensioner. Checked those yet. Also if you have messed with coolant during service you could have a trapped air bubble. You might try the Mos2 or motor oil saver from Liqiumoly, just a thought.

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#3390311 - 06/06/14 01:33 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
Marco620 Offline


Registered: 02/25/14
Posts: 207
Loc: Midwest, Rural KS
Running a PEA cleaner like redline si-1 might help. Sometimes if you run too low on petrol the fuel pump might be talking at you as well.

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#3390432 - 06/06/14 07:45 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
Trav Offline


Registered: 11/20/06
Posts: 9760
Loc: MA, Mittelfranken.de
With 60K miles on this 07 engine i am surprised by the rear seal and LIM gaskets.
These engines are not known for carbon knock, carbon knock is usually heard at cold start up and sounds almost like a rod knock, it may take 5 min or more to disappear but it does.

From what you describe i think you may be barking up the wrong tree, i don't think its in the engine. Some more information would be helpful.

*Do you any knocking when first started that disappears quickly and is not heard again the remainder of the running cycle?
*Have you been using the recommended viscosity since you owned it?
*Is this knock sound metallic or more like something moving and clacking like a solenoid?
*Any recent Check engine lights?
*Is this 3 knocks always 3 or does it vary in amount or frequency?
*Does this get louder with lower ambient temperatures?
*Do you hear an electric motor noise at start up or shortly thereafter?
_________________________
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#3390436 - 06/06/14 07:49 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
gregk24 Offline


Registered: 04/13/13
Posts: 2776
Loc: FL, USA
First of all welcome to BITOG! I honestly have no idea what the knocking noise is, I would however stop putting in oil additives, Techron is ok every now and then in the tank but all these oil additives could be doing more harm than good. If you want a safe and fairly inexpensive way to clean up the engine gently, start using a good synthetic oil like PU, PP, M1 etc.
_________________________
2006 Honda Accord LX 2.4 i-vtec 124.8K
HGSB 0w20 Fram Ultra
NXT: M1 0w20

2005 Chevy Uplander 3.5 116K
Castrol Edge EP 10w30 Fram Ultra
NXT: M1 HM 5w30

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#3390484 - 06/06/14 08:59 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
ARCOgraphite Offline


Registered: 05/17/09
Posts: 8531
Loc: N.H, U.S.A.
Only three knocks? Might be ABS check.
_________________________
2014 Nissan Note S 5MT, OC#1 1630mi-PGB 5W30+NISSAN Mexico 65f0c Filter
2015 Forester 6MT 5Door, OC#0 3370mi-FACTORY 0W20(?)+TokyoRoki 160 Filter

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#3390504 - 06/06/14 09:35 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
brandini Offline


Registered: 10/08/09
Posts: 974
Loc: Richmond, VA
If it's a the same MPG the first start after it sits, it could be the ABS check.

My car does it at 15mph, thought it was bearing or CV related for the longest time but I can go from park to neutral and coast down a hill and it still does it, but only once.
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#3390618 - 06/06/14 11:24 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
Nick1994 Offline


Registered: 02/19/13
Posts: 1102
Loc: Phoenix, AZ
Could be the famous GM piston slap?
_________________________
2004 VW Beetle TDI 160k
(Yeah it's a chick car but it gets me 40 mpg)

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#3390622 - 06/06/14 11:30 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
ARCOgraphite Offline


Registered: 05/17/09
Posts: 8531
Loc: N.H, U.S.A.
Mice hitting the fan on the way scrambling off the UIM?

May just be accessory belt memory with a quick backslap. TRy a new belt if the current one is ancient - also check that the tensioner is free.
I'm really hoping its not coolant pooling in a cylinder, but it sure could be.
_________________________
2014 Nissan Note S 5MT, OC#1 1630mi-PGB 5W30+NISSAN Mexico 65f0c Filter
2015 Forester 6MT 5Door, OC#0 3370mi-FACTORY 0W20(?)+TokyoRoki 160 Filter

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#3390632 - 06/06/14 11:44 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
npfd Offline


Registered: 06/05/14
Posts: 9
Loc: Canada
Thank you everyone, and welcoming me too Greg.

I forgot to add that yes we did the Coolant drain and refill. We checked a few times with the bleeder so that there is no air.

As for additives, I've only used the Auto RX, and the Techron.

I haven't really checked the belt/tensioner... thought I do hear a slight rattle or pinging on acceleration at times.. thinking it could be the loose heatsheild..

@Trav, the LIM might have been a bad call.... as it was wet around the area, the RMS leak was there when we bought it, back of oil pan and side wet... valve covers felt dry in the back... and the front

*Do you any knocking when first started that disappears quickly and is not heard again the remainder of the running cycle?
- at times a rattle.... at first but don't hear it again.

*Have you been using the recommended viscosity since you owned it?

- yes its the 5w30 with the approved GM standard, 6094.. I think..

*Is this knock sound metallic or more like something moving and clacking like a solenoid?

- sounds metallic, hammering... like a double knock

*Any recent Check engine lights?

- Not yet
*Is this 3 knocks always 3 or does it vary in amount or frequency?

- Rarely it varies.... sometimes it sounded faster and usually slower... I'm estimating here, the three knocks lasts about 2 seconds... Not enough time for me to press on the gas to see if its oil pressure related, as a friend suggested...

*Does this get louder with lower ambient temperatures?

- yes in cold weather used to be very loud last year, it is more audible in cold weather and warm weather, even in summer you hear it faintly.. very easy to miss if you're not looking for it... and in the winter if you have the radio on, you'll miss it.

*Do you hear an electric motor noise at start up or shortly thereafter?

Only when driving, after 20 feet I hear what I think is the ABS pump engaging...like a moan...

I'm still a bit stumped why I didn't hear it towards the end of the Auto RX treatment...

I managed to get the service records from the dealer, hard a hard time, and they did oil changes like every year, at about 10k kms...

At times there is a surge at idle, a clunk noise on acceleration, sometimes trouble starting...

Thank you all for the input.

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#3390638 - 06/06/14 11:51 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
supton Online   content


Registered: 11/09/08
Posts: 4731
Loc: NH
I think it's a bad mount. Stuff moving around. Find a watcher, open the hood, and try shifting from drive to park to reverse, to make the engine rock a bit.
_________________________
2004 VW Jetta Wagon, TDI, 5spd manual, 299kmile, his
2011 Toyota Camry, base, 6spd manual, 80k, hers
2010 Toyota Tundra double cab, 4.6L, auto, 89k

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#3390698 - 06/06/14 01:15 PM Re: three knocks heard at idle after sitting overnight [Re: npfd]
npfd Offline


Registered: 06/05/14
Posts: 9
Loc: Canada
thank you for the input, forgot to mention happens when I'm stopped, the knock, or sometimes coasting to a stop....

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#3390816 - 06/06/14 03:25 PM Re: three knocks heard at idle after sitting overnight [Re: npfd]
Trav Offline


Registered: 11/20/06
Posts: 9760
Loc: MA, Mittelfranken.de
Will it make any noise if you start it and just let it warm up or does the car have to be moving?
I have heard a noise similar to this which turned out to be a noisy electric AIR pump on a 3800 GM.
One that has failed will throw a CEL but the fan inside can wobble when its worn and strike the housing as it winds down to a stop.
That would be a heck of a long shot. LOL
_________________________
ASE L1, Master. Deutsch Meisterbrief.

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#3391081 - 06/06/14 09:06 PM Re: three knocks heard at idle after sitting overnight [Re: Trav]
edhackett Offline


Registered: 06/09/03
Posts: 1540
Loc: Sequim, WA



Sorry, I couldn't help myself. grin

Ed
_________________________
Never attribute to engineers that into which politicians, lawyers, accountants, and marketeers have poked their fingers.

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#3391890 - 06/08/14 12:28 AM Re: three knocks heard at idle after sitting overnight [Re: npfd]
npfd Offline


Registered: 06/05/14
Posts: 9
Loc: Canada
Thank you again for the input, lol at the song.... I do think I'm SOL..

I have remote started it and let it run for 10-15 minutes from afar didn't hear anything....

Usually happens when the car is stopped, at a red light, or let off the gas and moving.... Could the secondary air pump make that much noise? very audible in colder weather... btw I never knew this system existed.... and I Do hear it on the driver side of the motor... and strange thing when I had my head turned left, I thought I heard the knocking from the back too..... probably looking into it too much...

I'm still at a loss why I didn't hear it after the auto rx was in for a while....
Any way to test the secondary pump?

Thank you

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