Knocking noise at idle

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Hello everyone. Im new to the site and looking for some input on my issue. First some background information on the vehicle, its a 2002 trailblazer LS 4.2L with 112,000 miles. There is a slight knocking noise coming from either the back of the engine or possibly the torque converter area at idle up to about 1000 rpm, after that point it seems to go away. The engine runs very smoothly and there is no check engine light or pending codes. I have read that these engines can make some noise that is considered normal. I'll post a video of it in the next few days but any advice would be helpful.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
I also forgot to add that it seems to get slightly louder after the engine runs for about 30 seconds
 

81turboguy

Member
Nov 13, 2012
48
Subscribed to this, I have a similar tick on an 02. I'm not sure if it's piston slap or not. It doesn't annoy me that much but I'd rather know if it was an issue or not. Running 5w30 Mobil 1 with a Mobil 1 filter. I drove from Northeast PA to central Ohio and back this weekend and the noise is the same after running for 500 some miles.

How did your vid come out?
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Still haven't gotten around to making it yet. I should have it up by Saturday afternoon. And just as an update there is no change in the noise, but I have noticed that it doesn't actually started until there is oil pressure.
 

Sparky

Member
Dec 4, 2011
12,927
Mine has a little bit of noise sort of what you're describing, but I'm not sure exactly where from. But it runs fine, been doing it a long time, and has 175k miles and counting. I'm assuming yours isn't very audible?
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
I can honestly hear it more inside the cab than outside. Its more of an annoyance than anything else.
 

81turboguy

Member
Nov 13, 2012
48
Same here, inside the cabin. If I roll the drivers side window down, I can't hear it as much oddly enough.
I'll try to grab a vid this weekend also.
 

ShadowClutch

Member
Sep 5, 2012
88
Subbed. I will post a video of mine later. It makes an odd-rhythm tick up front by the fan, and a very regular tick near the intake. The sounds altogether are irregular and are not constant.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Heres the video and a link to it. [video=youtube_share;hN5dk0-JAJ4]http://youtu.be/hN5dk0-JAJ4[/video]
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
My mileage is right on point. Getting 11-12, but considering i drive 1.3 miles to and from work that isnt bad.
 

CaptainXL

Member
Dec 4, 2011
2,445
Zx2ner88 said:
The engine runs very smoothly and there is no check engine light or pending codes.

Right after you start it up I can hear the fan roaring which seems excessive. Then 4 seconds later I hear the knocking. I am going to take a stab and say your fan clutch is shot. To prove this run the engine for a few seconds with the belt removed. See if the noise goes away. If It was an internal engine issue we would hear the knocking right away, not a few seconds later after oil pressure builds up. Also as evident by your description that it sometimes doesn't make any noise.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
I actually did do that at one point but i forgot to mention. No change in the noise however
 

CaptainXL

Member
Dec 4, 2011
2,445
Try changing the oil again and use an ACDelco filter. Check the oil for any metal glitter. Use an oil pressure gauge and see if the pressure fluctuates. Possible spun bearing.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,028
Brighton, CO
I have never heard of a spun bearing that the noise went away with an increase to engine speed, I have only seen them get nosier, and louder.
 

Sparky

Member
Dec 4, 2011
12,927
CaptainXL said:
Try changing the oil again and use an ACDelco filter. Check the oil for any metal glitter. Use an oil pressure gauge and see if the pressure fluctuates. Possible spun bearing.

After seeing the reviews and teardowns of the AC Delco filters I would shy away from them. JMO.
 

CaptainXL

Member
Dec 4, 2011
2,445
Sparky said:
After seeing the reviews and teardowns of the AC Delco filters I would shy away from them. JMO.

Been using ACDelco filters for over 20 years with no problems on all my GM vehicles. The newer e-core PF-61e filters are the best design to come around since oil filters were introduced.
 

Sparky

Member
Dec 4, 2011
12,927
CaptainXL said:
Been using ACDelco filters for over 20 years with no problems on all my GM vehicles. The newer e-core PF-61e filters are the best design to come around since oil filters were introduced.

I never had a problem with them directly either, that I know of. However...

Oil Filter Comparison Study - GM Truck Central

The specific filter summary:
AC Delco PF1218 - GM Truck Central

It was one of the worst performing filters in their testing, so...

And a brief overall chart of the tested filters:
Untitled Document

That's why I'm not keen on the AC Delco ones anymore.

Now I'm not sure what difference there may be between that filter and the PF61e. I wouldn't think there would be, why would they build the various filters differently? Unless they are farming out various filters to various mfrs (like that one in the testing may have been built by STP). That is entirely possible. But then that can also open a whole new can of worms.
 

CaptainXL

Member
Dec 4, 2011
2,445
Yeah the overall build quality is much better in the PF-61e. Tons of reviews on Bob is the Oil Guy. For the price it is the best deal. The old design was graded a B and A in other categories. No way I am going to spend $$ on Amsoil or other expensive filters. Especially when the oil still needs to be changed based on OLM. Their testing at a 30um (micron). This is 30/1000th of a millimeter. This is basically like talcum powder. E-core Duraguard's trap particles down to 25 microns which would turn their tested F into an A.

BULLETIN ACD09-154

DATE: September 2009

TO: All ACDelco Distributors

SUBJECT: FILTER DESIGN CHANGE – PF46, PF47, PF52 AND PF61

Description

ACDelco is implementing a design change on the PF46, PF47, PF52 and PF61 ACDelco Oil Filters due to capacity constraints on the current product design. GM engineers have approved the new design which will begin to be incorporated in upcoming vehicle designs. This OE approved and manufactured filter provides the same Duraguard filtration performance as the previous design and specifically utilizes the original ACDelco media that traps particles down to 25 microns. Additional features include a slightly smaller can, fully covered baseplate, non-metallic end caps and high strength nylon core. This newly designed oil filter has the benefits of not only bringing excellent filtration performance, it is also environmentally friendly with components that can now be easily separated into steel, oil and parts to incinerate, resulting in less waste.
The Durapack versions of the newer design filter have begun shipping. The boxed or individually packaged versions will utilize the available production capacity on the original design, where possible, and will then begin to rollover to the newer design.
Effective Date
Immediately
Order Input
The current ACDelco short number will be used for the new design (interchangeable supersession). The system will automatically supersede to the new design.
 

Sparky

Member
Dec 4, 2011
12,927
Interesting info, thanks.

OK GM, what's up with the mixed bag of filters :crazy:
 

CaptainXL

Member
Dec 4, 2011
2,445
Sparky said:
Interesting info, thanks.

OK GM, what's up with the mixed bag of filters :crazy:

I don't think the previous filters from ACDelco had the "Duraguard" label. Must have better/different performance spec.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Ill try a new filter tomorrow and post any updates. I have a pennzoil filter on it now and im going to go with a purolator gold.
 

gmcman

Member
Dec 12, 2011
4,656
Have someone rev the motor up to about 1000-1200 RPM's and pull the electrical connector from each coil pack one by one. Generally if you have a bad rod bearing this will typically sniff it out.

This may or not throw a code but you can reset it if that happens.
 

ShadowClutch

Member
Sep 5, 2012
88
gmcman said:
Have someone rev the motor up to about 1000-1200 RPM's and pull the electrical connector from each coil pack one by one. Generally if you have a bad rod bearing this will typically sniff it out.

This may or not throw a code but you can reset it if that happens.

What are the expected outcomes of doing this?
 

gmcman

Member
Dec 12, 2011
4,656
ShadowClutch said:
What are the expected outcomes of doing this?

The knock will either go way or be drastically reduced if it's a rod bearing when you get to the bad cylinder. Listen to the change in pitch and you will know it when you hear it.

By removing the combustion the rod won't be slammed down into the crank, which generally is where the knock comes from.

If the bearing is spun or disintegrated then it will likely still knock but will not be as pronounced.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
gmcman said:
Have someone rev the motor up to about 1000-1200 RPM's and pull the electrical connector from each coil pack one by one. Generally if you have a bad rod bearing this will typically sniff it out.

This may or not throw a code but you can reset it if that happens.

Ill give that a go as well if the filter change doesn't do anything
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Ok i changed the filter and there was a significant reduction in the noise. I was also glad to not see a single spec of metal in the oil that can out of the filter.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Another update. I did some more diagnosis of the problem and i have some new results. I tried the spark plug trick and that had no effect on the knocking. I then took a piece of hose and listed to several different spots on the motor, couldn't hear the knock at all. So i took the inspection cover off of the bell housing, put the hose in a bit and listened. Im confident in saying that the knocking is coming from somewhere in there. I spun the flex plate to check for cracks and found none. Could it possibly be something in the torque converter? Also i couldn't hear it when listening to the transmission.
 

gmcman

Member
Dec 12, 2011
4,656
The bell housing could be amplifying the noise based on its shape. Can you get a sound clip from the bell housing area? Does the noise change in Drive?
 

CaptainXL

Member
Dec 4, 2011
2,445
Zx2ner88 said:
Ok i changed the filter and there was a significant reduction in the noise. I was also glad to not see a single spec of metal in the oil that can out of the filter.

I think your on the right track here. Seems to be valvetrain. If the noise was slight to begin with and now it is significantly reduced After using a new filter then what's the problem???

Can you provide another video for comparison? You used an acdelco PF-61e filter, right?
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Ill do my best to get a video where u can actually hear it. And i went with a purolator gold filter, not the ac delco
 

CaptainXL

Member
Dec 4, 2011
2,445
Zx2ner88 said:
i went with a purolator gold filter, not the ac delco

The question is why? Your trying to solve a problem and you are experimenting with different filters other than what came with the engine from the factory?! I would use an Acdelco PF-61e filter, use 5w-30 oil and do a flush to rule out the filter and oil as a problem.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
CaptainXL said:
The question is why? Your trying to solve a problem and you are experimenting with different filters other than what came with the engine from the factory?! I would use an Acdelco PF-61e filter, use 5w-30 oil and do a flush to rule out the filter and oil as a problem.

Ill try that filter at my next oil change, funds are a bit low at the moment. I did use a syn blend 5w30 at the last change. And what would you recomend for a flush?

@gmcman: yes i did try to tighten the bolts with a socket
 

jeffro312

Member
Oct 4, 2012
442
East Haven,Ct
A quick question. So the use of a non acdelco filter causes issue with our engine??? I had oil changed by a shop free asked for synthetic but not sure what they gave and filter was a no name car quest filter. So I changed to valvoline synthetic and not sure what filter came with auto zone special I just know its not acdelco. Got a slight knock at idle
 

CaptainXL

Member
Dec 4, 2011
2,445
jeffro312 said:
A quick question. So the use of a non acdelco filter causes issue with our engine???

There shouldn't be any problems. The only reason I would like to see an acdelco PF-61e used is to rule out any other filter as a cause. I don't keep track of filters that are compatible. Especially if the op says that a certain brand was installed but they don't know what exact part number filter.
 

Zx2ner88

Original poster
Member
Jan 2, 2013
51
Just to bring this thread back from the dead, I will be posting a video from under the vehicle tomorrow. I also plan on removing the torque converter bolts and running the engine to rule out that the noise is coming from the transmission. If the noise goes away after the bolts are out would that indicate a possible crack in the flex plate?
 

nopaybob

Member
Apr 3, 2013
97
Zx2ner88 said:
Just to bring this thread back from the dead, I will be posting a video from under the vehicle tomorrow. I also plan on removing the torque converter bolts and running the engine to rule out that the noise is coming from the transmission. If the noise goes away after the bolts are out would that indicate a possible crack in the flex plate?
Is that even possible or safe?

My 2002 W/ 220294 mile sounds the same as your vid.
I'm using mobil 1 oil and mobil 1 filter
Mine quiets down some after being warmed but is still there. Seems louder at times than others
Do you put in the 87 octane?
I just filled with cheap gas the other day, Today the knocking seems more prominent.
 

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