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rage123 05-16-2011 04:02 PM

try figuring this one.
 
I run a shop out of arkansas and have a problem with a 97 chevy tahoe 5.7 lt. Problem is, it is knocking but didnt prior to having the entire intake replace by one of my guys. only reason for replacing intake was because he broke one of the coolant ports off. There is no antifreeze or anything else like that in the oil. Im not sure if he did something wrong which caused this and he is just trying to cover it up or what. Ive checked the oil pump driver and seemed fine. if anyone has ever seen this or has any other ideas please let me know. Thanks.

T-bucket23 05-16-2011 05:01 PM

Did he use one of those brown disks to clean the intake surfaces. If he did and any of it got into the engine, it will wipe the bearings.

1ownerT 05-16-2011 05:16 PM

My last work truck was a 04 Chevy with the 5.3. On some occasions it would knock like crazy on start up, at other times no noise.

cobalt327 05-16-2011 05:26 PM

Quote:

Originally Posted by rage123
I run a shop out of arkansas and have a problem with a 97 chevy tahoe 5.7 lt. Problem is, it is knocking but didnt prior to having the entire intake replace by one of my guys. only reason for replacing intake was because he broke one of the coolant ports off. There is no antifreeze or anything else like that in the oil. Im not sure if he did something wrong which caused this and he is just trying to cover it up or what. Ive checked the oil pump driver and seemed fine. if anyone has ever seen this or has any other ideas please let me know. Thanks.

I would do an oil and filter change and cross my fingers if it's a bearing noise- which should be determined as best as possible. I've had good results listening w/a stethoscope to isolate the location of the noise- it may not be bearings.

eloc431962 05-16-2011 05:31 PM

X2 on the oil change, I have seen this before also and if it wasen't a bearing it was the oil-pump. JMO



Cole

Dave57210 05-16-2011 06:26 PM

knocking
 
Is there just enough of an intake air leak to make one or two cyl run lean and detonate?

willowbilly3 05-16-2011 06:57 PM

I'm thinking he dropped something down the intake which imbedded in the top of the piston.

eloc431962 05-16-2011 07:09 PM

Quote:

Originally Posted by willowbilly3
I'm thinking he dropped something down the intake which imbedded in the top of the piston.

That is a very good possibility, good call on that. :thumbup:


Cole

carsavvycook 05-16-2011 07:33 PM

Quote:

Originally Posted by rage123
I run a shop out of arkansas and have a problem with a 97 chevy tahoe 5.7 lt. Problem is, it is knocking but didnt prior to having the entire intake replace by one of my guys. only reason for replacing intake was because he broke one of the coolant ports off. There is no antifreeze or anything else like that in the oil. Im not sure if he did something wrong which caused this and he is just trying to cover it up or what. Ive checked the oil pump driver and seemed fine. if anyone has ever seen this or has any other ideas please let me know. Thanks.


Could be timing related. That one should be set at 0 degrees, and electronically adjusted with a scan tool. The engine rpm needs to be raised/goosed above 2000-2500 rpm, then let idle, for each distributor movement/timing adjustment, until it is set at 0 degrees timing (on the scan tool).

Hope this helps.

Stephen

rage123 05-17-2011 07:21 AM

hmmmmmmmmmmmmmmmmmm
 
Thanks for the replys guys. Im 100% on the rod noise as it sounds likes it gonna come through the side of the block. Regarding the brown sanding discs, Ive never heard of these causing problems as long as u cleaned up afterwards and we do use these little 2" discs regularly. However, I will probably find something else to use then since I don't wanna take any chances. It is a very big possibility that he could have dropped something in the motor or left something in there like rags or something like that. It wouldnt surprise me it the intake isnt sealed very good as he seems inexperienced with this kind of procedure but its not a spark knock or detonation. Timing was a couple of teeth off which has been corrected. This guy is no longer working for me since he was caught using drugs in the bathroom which explained the numerous trips to the bathroom ha ha. I figure the motor is pretty much trashed so I dont think Im gonna tear it back down since time is money and since I have to provide a new motor anyways(about 1200).

T-bucket23 05-17-2011 07:53 AM

Quote:

Originally Posted by rage123
Thanks for the replys guys. Im 100% on the rod noise as it sounds likes it gonna come through the side of the block. Regarding the brown sanding discs, Ive never heard of these causing problems as long as u cleaned up afterwards and we do use these little 2" discs regularly. However, I will probably find something else to use then since I don't wanna take any chances. It is a very big possibility that he could have dropped something in the motor or left something in there like rags or something like that. It wouldnt surprise me it the intake isnt sealed very good as he seems inexperienced with this kind of procedure but its not a spark knock or detonation. Timing was a couple of teeth off which has been corrected. This guy is no longer working for me since he was caught using drugs in the bathroom which explained the numerous trips to the bathroom ha ha. I figure the motor is pretty much trashed so I dont think Im gonna tear it back down since time is money and since I have to provide a new motor anyways(about 1200).

I have seen several cases of engine failure after cleaning with the brown scotch brite looking disks

rage123 05-17-2011 07:58 AM

but?
 
How did u realize the discs was the cause of youre engine failures? Did u tear one down and find sediment on the bearings and oil passages? Just curious

T-bucket23 05-17-2011 09:03 AM

Sent oil out to be evaluated. All instances found silicates (abrasives) in the oil. These were not jobs we originally did. We saw them after intakes had been done and original shop said it could not be anything they did.

cobalt327 05-17-2011 09:11 AM

Not arguing w/anyone, but it would seem to me that the particles that are large enough for the filter medium to filter out should leave only particles small enough to easily pass through the oil clearances of the bearings.

OneMoreTime 05-17-2011 09:54 AM

Quote:

Originally Posted by cobalt327
Not arguing w/anyone, but it would seem to me that the particles that are large enough for the filter medium to filter out should leave only particles small enough to easily pass through the oil clearances of the bearings.

All it takes is real fine particles like a polishing rouge to wipe out a set of bearings. You can't see them or feel them but they will show up in an oil analysis..


Sam


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