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.
Knocking noise at idle
- Thread starter Zx2ner88
- Start date
I also forgot to add that it seems to get slightly louder after the engine runs for about 30 seconds
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?
How did your vid come out?
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.
I can honestly hear it more inside the cab than outside. Its more of an annoyance than anything else.
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.
I'll try to grab a vid this weekend also.
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.
Heres the video and a link to it. [video=youtube_share;hN5dk0-JAJ4]http://youtu.be/hN5dk0-JAJ4[/video]
Somewhat similar to mine. Almost like a spun bearing. What kind of MPG are you getting? My city, which is what I do more of currently, is 11-12 but my highway is around 18-19.
Here is my noise.
Tapping, knocking noise 02 TB 93k
Here is my noise.
Tapping, knocking noise 02 TB 93k
My mileage is right on point. Getting 11-12, but considering i drive 1.3 miles to and from work that isnt bad.
Zx2ner88 said:
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.
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.
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 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.
Sparky
Member
- Dec 4, 2011
- 12,927
CaptainXL said:
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.
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.
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 said:Interesting info, thanks.
OK GM, what's up with the mixed bag of filters
I don't think the previous filters from ACDelco had the "Duraguard" label. Must have better/different performance spec.
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
ShadowClutch said:
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.
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.
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.
Zx2ner88 said:
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?
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
Zx2ner88 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.
CaptainXL said:
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
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
jeffro312 said:
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.
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
Is that even possible or safe?Zx2ner88 said:
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.
