NEED HELP Weird top end knock

[edibleMango]

Hey all. I am new to this forum but I have found other posts on here to be useful so I figured this would be a good place to ask my question.

Last year I bought a 07 TB with the 4.2. It has about 230,000 on it but its in beautiful shape. I just rebuilt the front diff on it about 2k miles ago and everything has been running amazingly until this morning. The truck had been parked for about a month due to my traveling for work. I went out to start it and it started right up without issue. I walked away to let it warm up but when I came back (about 5 mins later) I could hear some irregular knocking not rhythmic at all. It honestly sounded like a bad AC compressor to me AND it only knocked when the AC clutch was engaged so I passed it off and shut the ac off. The sound disappeared initially. Only when I put it in gear and the revs dropped slightly it came back.

Facts:

• The knock is very loud at the front corner of the valve cover just above the VVT cam-phaser.
• Revving the engine slightly (about 1000 RPM) makes the knock disappear and it does not seem to come back even up to around 4000 RPM. However once the RPM drops back down for a second it will come back.
• Changed the oil about 1000 miles ago. Used a different brand of oil than normal. 5w30 full synthetic ultra platinum Penzoil.
• No codes - although it has not run for very long since it started knocking.

What I have tried:

• I started by removing the serpentine belt and running it for a sec. I put it in gear with the parking brake engaged and could hear the knocking. This rules out the PS pump, Water pump, Alternator, AC compressor, Tensioner, and fan clutch.
• I then replaced the VVT Solenoid just in case it was stuck open and causing oil starvation to the chain tensioner. No dice. It is worth mentioning though that the old solenoid was clean as a whistle.
• I decided to remove the valve cover and take a look. Expecting to see something obvious. I was disappointed - It is the cleanest 230k engine I have ever laid eyes on lol.

Trying to figure out where to go from here. I was thinking to replace the cam-phaser next but I am wondering if anyone has had anything similar to this. I found a post by Mooseman from several years ago mentioning that their knocking went away with a bit of oil pressure due to a bad hydraulic chain tensioner. This seems to also make sense because a bit more rpm causes the knock to go away.

Video of it knocking:

Video of the internals after removing valve cover:

Hoping to find a resolution here soon as my wife wants her TB back!

 

[mrrsm]

Welcome to GMT Nation...

C-A-U-T-I-O-N ... As soon as you get the chance.. Douse the Valve Train with a Water Displacing Lubricant like WD-40. As long as the Valve Cover is off the top of the engine and unsealed without 89 Inch Pounds holding pressure upon Brand New VC Gaskets... the exposed, worn area of the Cam Lobes have the least amount of lubrication... and they WILL Rust Up... Tuit De Suite... as soon as ambient, humid air hits them.

Any Engine Codes in Memory? P0014, P0017, P0345?

Your impression from @Mooseman 's Thread dials in on a completely extended Timing Chain Tensioner that is designed to normally take up the RETURN Slack since the Clockwise Engine Rotation keeps tension on the Intake side of the Timing Chain would snug up since the internal Hydraulic portion of the Tensioner works better with Higher Oil Pressure being generated at Higher RPM. Once it "Ratchets" to its full extension... That is IT... with the exception of a small boost from internal Oil Pressure.

Nominal 12 PSI Oil Pressure at Idle won't be enough to keep up that residual Timing Chain Tensioner Shoe Pressure pushing against the Passenger Side Timing Chain Guide... Right where the Clicking-Clacking Noise in your Motor is Most Evident.

Thus, this invites the free motion of the loose chain to *rattle a little bit at random* at Engine Idle as soon as the Metal Links and Side Plates of the Timing Chain expand with additional engine *Heat Soak* and then echo up inside that hollow chamber inside of the Upper Engine and under the Aluminum Valve Cover.

This noise may subside as the Oil Pressure can increase to 65 PSI @ 3,000 + RPM and make the noise lessen as the Tensioner moves slightly tighter against the "Loose" Return Side Chain Guide during the Chain's rotation.

This is a very High Mileage Engine and even as well cared for as THIS Motor obviously is... the Worn in Chain Guides and S-T-R-E-T-C-H-E-D out inter-links can combine to change the Timing Relationship between the Crankshaft Cog, the Cam Phaser Gear and Intake Sprocket.

This motor can become unmanageable with as litlle as 2 Degrees of Timing Variance, making EFI and Spark Plug Ignition Timing impossible to reconcile via the PCM.

Even with all of the added work involved with pulling the Front Timing Cover and the Crankcase - Oil-Pan, changing out the entire Timing Chain Set at One Go will reward you with a much renewed and reliable Motor.

Avoid using anything other than the Full Cloyes Timing Chain Kit... (RockAuto) Best for the Quality needed here.



"Pain is good if it results in the satisfaction of fixing it yourself..." @Mooseman

 

[Mooseman]

It's the timing chain tensioner. I know because I had the EXACT same symptoms, noise and absence of it at any RPM higher than idle. Sorry to tell you that you're in for a world of hurt to fix it, and I got the scar to prove it.

How to replace I6 timing chain and tensioner

 

[edibleMango]

Thanks @mrrsm for the reply and @Mooseman for the confirmation. Gives me confidence that I will be able to get her back on the road in due time. I started tearing into her today - My goal was to get all the stuff up top taken off to then move on to the underside at a later date.

Here is a video of the progress so far:

Does anyone know which cam-phaser I need to order? I have heard there are different variations available. How can I tell which one fits my application?

So far it looks like I will be ordering:
Cam-phaser
Cloyes timing kit
Cam-holding brackets from amazon
Valve cover gasket
Water pump + gasket + bolts
Crank pulley bolt
A threaded rod (m14x?) for installing crank pulley
Tensioner pulley
A tube of RTV for timing cover and oil pan

Is the pickup tube on this engine anything like the 4.3 or 3.6 where the sealing surface must have a new seal each time otherwise you will not be able to build pressure?

Did I miss anything? Is there any other TTY bolts I will encounter?

 

[Mooseman]

You're well on your way. The timing chain cover gasket set will have a new pickup tube gasket, which yours is the newer flat type rather than the early version o-ring. Both versions are included in the kit. It will also have the water pump gasket however only the Mahle will have the metal type that originally came with this engine.

For the cam phaser sprocket, it goes by the year. On my 02, I got a Dorman the second time I replaced it as the ACDelco rebuilt one, which doesn't seem to be available anymore, did not last. The Dorman lasted over 100k km until the truck was scrapped for transmission issues.

 

[Mooseman]

Rechecking your parts list, the Victor Reinz and Mahle kits include the RTV.

And with the experience I have now, I would also recommend taking the oil pump apart and inspecting the internals, including the pressure regulator/bypass. If in doubt, I would rebuild the oil pump as some have had oil pressure issues with the higher mileage units. Looking at what's available on RA, you basically get the one half as the other half is built into the timing cover. They list pumps and repair kits but looking them over, they are basically the same. I'd go with either the Sealed Power or Melling.

If you opt out of rebuilding the pump, I'd take it apart and give it a cleaning and ensure the bypass is working well and doesn't bind.

 

[mrrsm]

I can't assume that you have already done the following, but these are very important considerations worth mentioning before you proceed taking anything else off of the Motor:

(1) This Line Diagram shows the Timing Chain ID Links and their relationships to the Sprocket Markings on the Intake Cam Sprocket, the Cam Phaser Sprocket and the Crankshaft-Oil-Pump Slip On Cog at the 5 O'clock Position and the word "DELPHI" on the Cam Phaser should be Level with the Upper Edge of the Engine Block.

To rectify this circumstance, Re-Install the Old TTY Crankshaft Bolt and Rotate the Engine for as many as Fourteen Rotations (Yup...14 Xs) ...in a Clockwise ONLY Direction until you achieve THESE Views:



This referencing MUST all be achieved with the #1 Piston positioned at Top Dead Center and the Rear of the Intake and Exhaust Camshaft Flats being Horizontal, Level and Facing UP to be then held in place using THIS Tool to ensure that the Engine is NOT 180 Degrees Out Of Phase before removing the Timing Chain Set::

Amazon.com

(2) As you go forward... Having THIS Link as a resource will help enormously with knowing the majority of the Parts, Part Numbers, Pieces and Gasket Kits required for an ENTIRE Engine Build for the GM 4.2L LL8 Engine:

GM_04_42L_NEW_ENGINE_PARTS

This Album contains images of Brand New Engine Parts and Components for the Complete Rebuild of the GM Atlas LL8 4.2L Engine for the years 2002-2004.

www.flickr.com

(3) Refer to the images in THIS Album for the proper K&M Harmonic Balancer Removal and Installation Tools:

GM 4.2L HARMONIC BALANCER TOOLS

These Images display BOTH the Early Model Harmonic Balancer Removal Tools AND the Late Model HB Tools in use for the GM Atlas 4.2L Engines.

www.flickr.com

(4) When the time comes to Install a Brand New TTY Crankshaft Bolt, it is imperative to restrain the Crankshaft by passing a 15MM Long Impact Socket held with a Breaker Bar...through the Plastic Plug Covered Hole in the underside of the Crank-Case-Oil Pan, Rotate one of the three Torque Converter Bolts around to align with that Hole in the Pan and slide the 15MM Socket through and use it to prevent the rotation of the Crankshaft when applying 110 Foot Pounds of rotational force---PLUS--- Marking the Face of the TTY Bolt with a Vertical Line. Then...Rotate the Bolt Clockwise 180 Degrees from the 12 O'clock to the 6 O'clock position to achieve Final Torque To Yield Bolt Stretch:





(5) Before applying any Permatex High Temp Gray Silicone around the Flange areas of the Crankcase and Timing Cover, be fastidious in cleaning and using a Linoleum Razor Blade (taped off on one side for safety) and used by dragging it backwards to clean the Old Sealant away. Likewise, all of the indented lines should also be cleaned so as to look THIS Good:





...and Watch "Duane" from RealFixesRealFast applying the ACDelco OEM Sealant to the Inverted Engine Block on an Engine Stand at around 9:06 into this Rare Trailblazer Body R&R and GM 4.2L LL8 Engine Swap Video...

Remember that by Threading in Two of the Crank-Case-Oil-Pan Fasteners into the positions encircled in RED in this Image, and slowly tightening them down evenly... You will be able to Break the Old Sealant Loose between the Oil Pan Flange and the Base of the Aluminum Engine Block and NOT have to rely on using any Prying Tools... DO NOT FORGET TO REMOVE THE TWO REAR LONG PAN FASTENERS ACCESSIBLE BY REMOVING THE LONG RUBBER PLUG ADJACENT TO THE REAR OF THE ENGINE BLOCK NEAR THE BELL HOUSING!!! :


THIS *Tip* comes from... @Mooseman

 

[Mooseman]

He doesn't need that balancer tool. He already got it off and it's for the first gen balancer, which was only for 2002

 

[mrrsm]

That *Flicker-Bucket* Folder has BOTH the HB Removal and Installation Tools... (Just being comprehensive for all Readers to source them...)

Continuing in regards to the Later Model Front Cover which include the Oil Pump from GM and the Aftermarket Oil Pick Up Tube that Melling sells with the Vacuum Seal Assuring Orange Silicone Grommet...vs... the Early Model *FUBAR* Prone Blue Viton "O" Ring Design... Here are some comparison images of these Components and Part Numbers from their OEM Folks.

Please Note... These two different Front Cover and Gerotor Oil Pump Components are NOT interchangeable:

 

[edibleMango]

Thanks @mrrsm for the detailed write-ups!

I haven't been able to work on it this weekend as I am still out of town on business but I am hoping that next weekend I might get a couple of hours.

I ordered parts today - thanks to the pictures @mrrsm provided it was a breeze to at least find the correct part numbers on most things. Finding the parts for sale was another thing entirely. After looking at RA, Ebay and Amazon I opted to order most things through Amazon due to cost and availability.

List:

P/N	Item	price	link	Note
85084​	Gray RTV (aresol)	$28.09​	https://www.amazon.com/dp/B000HBM4K6/?tag=gmtnation-20	I hate squeeze tubes.
917-262	Dorman Cam-Phaser	$65.77​	https://www.amazon.com/dp/B00QSLNF16/?tag=gmtnation-20	Amazon had best price.
TCS 45052	FEL-PRO timing cover gasket set	$22.84​	https://www.amazon.com/dp/B000Q0R53E/?tag=gmtnation-20	Don’t need RTV as ordered separate.
9-0195S	Cloyes timing chain kit	$163.93​	https://www.amazon.com/dp/B0031GS5BG/?tag=gmtnation-20	Amazon had best price
Chinesium	Camshaft holding tool	$17.99​	https://www.amazon.com/dp/B07QDHZWLF/?tag=gmtnation-20	It is a piece of steel - should work.
Chinesium	Harmonic Balancer Installer	$13.98​	https://www.amazon.com/dp/B08ZYRCNFY/?tag=gmtnation-20	Will see if this will work. Threads are M16-2.0 which is the same as what is listed for the LL8. My only worry is it might be too short.
M16-2.0x110	Harmonic Balancer Bolt	$16.16​	https://www.amazon.com/dp/B0CM8324SM/?tag=gmtnation-20	Another user mentioned that this worked.
M16x40x6	Harmonic Balancer Washer	$22.09​	https://www.amazon.com/dp/B079K5NKTQ/?tag=gmtnation-20	Only washer I could find.
VS50667R	Valve Cover Gasket Kit	$17.69​	https://www.amazon.com/dp/B0016ZNIY8/?tag=gmtnation-20	Amazon had best price.

Initially I was going to order the HB bolt through Ebay https://www.ebay.com/itm/255219897165 but the seller is out of town and it would not ship until June. So I opted to go with the other option as mentioned HERE.

I will plan to look into the oil pump and make a decision when I have my hands on it @Mooseman thanks for the suggestion.

I have also got a leak somewhere on the rack and pinion. Haven't got a close enough look at it to know whether it is where the steering shaft attaches or hydraulic lines or driver side inner tie rod so I will also have to take a look at that when its dropped out.

Thanks for all the help guys. I hope I have an update next week!

 

[mrrsm]

Great News! Remember to place a Dollop of either Mol-D Grease or a respectable High Pressure Grease along the Full Length of the Bolt Threads of the Harmonic Balancer Installer Tool Kit and include using the same *Stuff* in-between Flats of the Hardened Washers of your Chinesium Install Kit.

The last thing you want to do is have the Crank-Shaft Threads inside the Nose of the Crank accidentally get Stripped Out. Of course, using the New TTY Crank Bolt to perform ANY portion of this initial HB Installation... is Out Of The Question.

It goes in Bone Dry after everything else has been done with the Install Kit and the Factory application of the Thread Locker that has already been applied on the GM or OEM Quality TTY Bolt Threads is sufficient to keep it there after applying 110 Foot Lbs of Torque Plus 180 Degrees of Torque Angle to achieve all of the holding power required.

Remember to install the Friction Washer on the Updated Harmonic Balancer inside location Bone Dry and use No Spray Lubricant or Grease on the TTY Crankshaft Bolt. In the absence of having a Machined in Woodruff Key... It is the F-R-I-C-T-I-O-N Fit that holds the HB solidly against the Crankshaft and any added lubricant will defeat the purpose.

Ergo... AFTER using the HB Installer Bolt and Washer Set with Moly-D Grease ... Thoroughly Spray out the Crank-Bolt Hole with Brake-KLEEN or similar De-Greasing Solvent and let it air dry or use some Canned Air. Remember that the Crank-Shaft Fastener Hole is BLIND... so any left-over grease or detritus will NOT Compress and can prevent the TTY Bolt from entering as deeply as necessary.

One Last Mention... Make certain to purchase BOTH Timing Cover Seals and you can keep the one that does NOT Fit because the Updated TC is Different than the 2002-2004 Version. There have been some instances where using the Wrong Seal has resulted in a lot of extra repeat work after the Motor Oil decorated the Garage Floor.

 

[mrrsm]

Regarding issues with your Off Topic Power Steering Seal Leaks on the Rack & Pinion... THIS Threads provides a LOT of information on that Topic when you finally have the opportunity of investigating it:

Snapped bolt holding power steering line to rack and pinion

Need help. I was replacing the power steering lines due to rust and managed to over torque the bolt that attaches the lines to the rack and pinion. Does anyone know where I can find that bolt or the dimensions. I got the part out that snapped but need to replace it.

gmtnation.com

PS... Your Title will "*** Draw In Many More Viewers" if "MOD adjusted" to be something like, " 2007 Trailblazer 4.2L Timing Chain Overhaul"...



*** "Milkshakes" --Kelis on YT

 

[Mooseman]

PS... Your Title will "*** Draw In Many More Viewers" if "MOD adjusted" to be something like, " 2007 Trailblazer 4.2L Timing Chain Overhaul"...

No. We already have a thread with that subject, which is already linked. This is perfect for those that have this same knocking at the front of the valve cover.