Engine knock... from outta no where.

Chris E

Original poster
Member
May 6, 2016
17
Nashville Area
So I noticed today that our 06 TB with 4.2 i6 had a knocking sound... I noticed it when my wife was pulling in. Checked the oil and had to add a quart. That did not help obviously. I checked again when it was cold and the same thing.

Here is a link to a video some one posted with the same knocking (but with more pulley noise..)

Any ideas? I keep reading people saying it is the water pump or fan clutch but my ears cannot tell... but that's why I'm asking here. It is a little irregular at idle but becomes faster and more uniform under load. Almost sounds like a little troll is under the hood beating a small pot like a drum. :blinkhuh:

This vehicle is one of our commuters so I'm trying to keep it running as long as possible.
 

Sparky

Member
Dec 4, 2011
12,927
Well for one, you've got a nasty noisy pulley screaming at you too. Probably a bad idler.

Easiest way to tell if it is internal or not is take the belt off and start the engine (do it on a cool engine since you won't have coolant flow, and don't let it run too long because the battery will die). If the sound is gone it means finding the offender and fixing it. If it still knocks, it is inside the engine.
 
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Chris E

Original poster
Member
May 6, 2016
17
Nashville Area
Well for one, you've got a nasty noisy pulley screaming at you too. Probably a bad idler.

Easiest way to tell if it is internal or not is take the belt off and start the engine (do it on a cool engine since you won't have coolant flow, and don't let it run too long because the battery will die). If the sound is gone it means finding the offender and fixing it. If it still knocks, it is inside the engine.
Thanks Sparky, that is a good place to start. Also, that is someone else's video. I just linked it because that's what my TB sounds like right now. I too noted that pulley noise.
 

Chris E

Original poster
Member
May 6, 2016
17
Nashville Area
Pulled the belt, ran the engine, knock was still present...

Is there any hope that this is something minor in terms of engine repair?

Is this common? We just broke to 200k mark but I've been militant about vehicle maintenance and recently replaced the rear end with a locker so this is depressing. :hopeless:
 

littleblazer

Member
Jul 6, 2014
9,265
If its wrist pin knock you can run it for a long time before something happens...
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
Its early in the investigation...so reading some prior posts that lead from the simplest solutions to the more complex only if drastic action is involved will be a good course of action. The below listed should be considered “required reading” or prior posts along those lines...and if you can provide the Members with a Good “walk-around” set of videos that hover around the engine from top to bottom to help in pin-pointing the problems and make suggestions is always very helpful is sorting things out sooner than later… otherwise ...it can just be a big guessing game in the absence of symptoms that are clearly explained. Here are a few On Topic GMT Nation Member Prior Posts that are worth looking through:

From @Capote ...and his <FIXED> conclusions occurs with a “Happy Ending” involving the R&R of a Cracked Flex-Plate as the source of all the Racket:

http://gmtnation.com/forums/threads...ll-knocking-bottom-end-troubleshooting.15534/

...and from @holytornado … as his videos are a perfect examples of how to gather good information:

http://gmtnation.com/forums/threads/rough-idle-and-knocking-noise-from-bottom-of-motor.16220/
 

smt 59

Member
So after listening to the clip your knocking noise is a rod bearing, I have had a lot of experience with these. You should fix asap, if you don't and it completely goes you will require a new engine.
 
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gmcman

Member
Dec 12, 2011
4,656
I agree that it sounds like a rod bearing. It's a real pita, but if you have some time and the mechanical abilities, I would pull the oil pan and see what's going on in there. Hopefully, you can just change the rod bearings but making sure the crank journal is round is also key. If you keep driving it the crank will need to be removed for sure.
 

smt 59

Member
I'm pretty sure the crank maybe damaged at this point, the knocking is really pronounced. I did not check the profile but if your 4WD the job just got bigger as the shafts go through the oil pan.
 

Chris E

Original poster
Member
May 6, 2016
17
Nashville Area
Thanks for the input everybody.

I noticed this morning that the knock was not present at cold start but was there after it warmed up.

@smt 59 it is a 4WD.

What would be a reasonable price to have the work done by a private mechanic? I do not have the resources to take care of this one on my own.
 

littleblazer

Member
Jul 6, 2014
9,265
Put thicker oil in to mask it? :crazy:

I don't know pricing but it should be drop the pan and swap the rod bearings... but being as that kind of sucks I don't really know.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Usually, when an engine develops a knock like that, it's replacement time. Probably cheaper and likely more long term solution. With that rod knocking lime that, the crank is likely compromised and also the rod itself. Eliminate the guesswork and replace the whole thing.
 

Chris E

Original poster
Member
May 6, 2016
17
Nashville Area
@Mooseman - I was afraid someone would say that because that's my own mentality. There was a small part me of hoping I could get a little more than 200,100 miles out of this one :cry:

Looks like I'll be shopping for a new truck this weekend. Its been a good 11 year run I suppose...

I'll standby on this thread to see if we can come up with anything else in the short term.
 
Last edited:

smt 59

Member
I agree with Mooseman, it's better to replace the engine at this point as once it comes apart it just keeps snow balling. Good luck with the search.
 

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