4.2 mysterious knock HELP!

[Goodfella]

I have a 2008 trailblazer 3LT 4.2. This truck has never used oil. I must admit due to my 7 day work schedule, the routine maintenance often gets put on the back burner. It started with a low oil shut engine off message while on an incline of a boat ramp. I'm ashamed to admit it was down almost 4 quarts. I topped it off and had to help son move back to college the next day 100 miles away. I swallowed my pride and paid the local valvoline 100 bucks for a full synthetic change. I drove it to his school, and pulled a 16ft trailer back. On the way home I thought I noticed a tick on the highway only when decelerating with throttle off. A few days later I heard a loud knock/clatter and my heart sank. At this point I was sure the engine was done. Once warm it has a barely noticeable knock at idle. If u bring the rpms up the loud knock comes on about 1900rpm and disappears around 2500. I put a stethoscope on every inch of motor and pinpointed it to valve cover right over cam phaser and timing chain. I compression tested it and had 245,230,240,240,220,230. I pulled the vvt solenoid and screens were clogged. I currently have the valve cover off and can see nothing obvious.i can move the phaser ever so slightly with alot of force. The chain seems tight and looks ok. I have owned this since new and it has 130,000 on it now. I dont mow if i should replace all the timing components, or just solenoid, sensor, and phaser. The only work that has been done is water pump, hubs, etc. And the diff did fail at about 100,000, which i did myself(it was rough), but thats it. Any insight or opinions would be greatly appreciated

 

[Goodfella]

I forgot to mention it is throwing no codes. Everything I read that is similar all have check engine light and codes when scanned.

 

[mrrsm]

Judging from the Varnished Up Valve Train and the indelible symptoms of Low Oil Pressure (With Clatter in the Engine) your Oil Pick Up Tube has been almost Varnished SHUT. The link to this First Video will guide you (courtesy Kevin Nadeau) through his own journey with this repair...and if you decide to follow in his lead... Seek Out..Download and Watch ALL Five Videos B4 doing ANYTHING so you can benefit from his admissions of making mistakes that need to be avoided:

Ordinarily... many of us would recommend filling the Crank Case with 6 Quarts of Cheap Organic Oil and the rest as Transmission Fluid (One Quart)...then after starting the Engine and allowing to IDLE (NO Racing The Motor) for around 5 Minutes... Shut it down and then Change (and save the Oil Filter for an Autopsy to find out what came loose inside there) the Oil and Filter Using a Cheap One with 7 Quarts of New Organic 5W-30 Motor Oil.

Start and Warm Up the Engine again ...and if your Oil Pressure becomes Normal and No Noise happens with a VERY GRADUAL increases in RPM... Then Drive the SUV for a few Days and Repeat this entire exercise. If afterwards... your Oil Pressure remains nominal... you may have Dodged a Bullet. But... Judging from the Blackened Intake Camshaft Bearing Cap.... I suspect that at the very least.. That Aluminum CAP will have some underlying friction overheating damage and perhaps even have Blued the Camshaft Journal. Do not run this Motor if you hear any Clatter!

Before doing the above suggested Engine Flush Procedures... I would suggest that you also follow @MAY03LT 's Instructions in these Videos concerning installing an Oil Gallery Plug Adapter... and an Analog Oil Pressure Gauge and WATCH that item closely for the requisite 60+ PSI...Kevin shows you what HIS diagnosis was on his First Video as well:

 

[I_Shoot_Back]

It's not a rod knock?

 

[mrrsm]

Symptomatically ... Rod Knock usually presents heavier at idle and lower RPM and gradually disappears at higher RPM due to enough centrifugal pull from the rotating Crankshaft . But... I would NOT recommend raising and lowering the RPM trying to test any "theories" because with a large amount of play... the loose Connecting ROD(s) could gets jammed at Higher RPM... and can easily punch a hole through the side of the All Aluminum Engine Block and destroy this Motor. if your Main Bearings Journals went Bone Dry ...even for a few seconds at Higher RPM during such an Oil Starvation... those Aluminum Silicate Bearings would melt like butter into the Crank Journals. If you watch this last video...you can easily perform a Rod Knock Test:

 

[Mooseman]

Sounds like it could be a lifter if the noise is on top. I would actually do an engine flush using flush and then put in 6 quarts of oil and one of transmission fluid and drive it a while. The ATF won't lower the viscosity that much but will do a long term cleaning of the innards. The oil might get dirtier faster so plan on an early oil change. The flush and ATF might just unclog the pickup if it's clogged.

And yes, you should do an actual pressure test using a gauge.

 

[Goodfella]

I guess im gonna have to bite the bullet and take the pan off. Starting to think a swap with another engine might be a good idea

 

[Goodfella]

Do you think the phaser is ok? I dont know how to tell.

 

[mrrsm]

First Things First... Since you have the Valve Cover removed...follow up with @Mooseman 's idea about the Valve Train and reach out and try to move each and every Rocker-Pushrod Assembly for all 24 Valves on the Valve Train... if you find any that are Loose or Broken... then you are STILL in a good position to repair the problem since the entire Valve Train sits right there and is easily accessible. If you find nothing there and can use the McDonald's Straw and Screwdriver technique shown in the video of Post #5... doing this Test on an In-line 6 Cylinder like the GM Atlas 4.2L Engine is a Walk In The Park. If you find any Spun Rod Bearings during this Test... Put Down the Shovel... and Stop Digging... you will need to pull the engine out... no matter what.

There was a contemporary Thread started by @limequat today concerning a discussion of ideas about locating a Pick N Pull Motor ...or just buying a Good Used one from LKQ Online if it comes down to it. If you intend on pulling the Crankcase and Timing Cover... you can also observe and try to move around the Con-Rods from below and also will probably see the damage caused by over-heating near the Rod Caps with a Bright Flashlight. There again... if you can confirm Lost or Spun Bearing Pieces in the Bottom of the Oil Pan... Put Down The Shovel and Stop Digging. You will need a Motor ... so doing anything else to it other than getting the damned thing out of there will be wasting your time and effort.

 

[JerryIrons]

Symptomatically ... Rod Knock usually presents heavier at idle and lower RPM and gradually disappears at higher RPM due to enough centrifugal pull from the rotating Crankshaft . But... I would NOT recommend raising and lowering the RPM trying to test any "theories" because with a large amount of play... the loose Connecting ROD(s) could gets jammed at Higher RPM... and can easily punch a hole through the side of the All Aluminum Engine Block and destroy this Motor. if your Main Bearings Journals went Bone Dry ...even for a few seconds at Higher RPM during such an Oil Starvation... those Aluminum Silicate Bearings would melt like butter into the Crank Journals. If you watch this last video...you can easily perform a Rod Knock Test:

That's a great video

 

[Goodfella]

Ok sounds good. I will inspect the valvetrain and rod bearings tonight as you suggested.Thanks again. I will let you know the results.

 

[Goodfella]

Well i didnt get a chance to even touch the TB last night. The vehicle im currently depending on[95 s10 4.3] demanded my attention yesterday as I started it leaving work. I heard a faint knock on startup which got my attention and caused me to notice the valves ticking at idol. When it rains.............
My son(engineering student) has had it at college for the last three years and its safe to say it's been rode hard. Was running good when he was at home but now needs attention. I cleaned the throttle body and spacer he put on it. Then i followed the clean up procedure you outlined by changing oil with cheap conventional and a quart of atf. I have a full set of manuals for this truck and am guessing there is a procedure to adjust the valves? Man........im getting close to ordering that new midnight edition ZR2......lol

 

[Goodfella]

Im planning to resume work on tb tonight.....sorry if that was off topic......new to this forum stuff

 

[littleblazer]

The valves on the 4.3 by are easy. Loosen the rocker until it taps, then slowly snug it until you don't hear it anymore and then just throw half a turn on it after that. Rinse and repeat.

 

[Mooseman]

Yeah, should stay on topic. If you're having issues with the S10, you should start a new thread in the Other section.

 

[Goodfella]

Parts will be here tommorrow.....have decided to replace phaser, solenoid, sensor. Then i will flush it while monitoring mechanical oil pressure. My question is do you think my discount kent moore chain retention tool will work? Or should i bite the bullet and buy the real thing? Didnt wanna wait a week for one or spend the money for a tool ill prob use once. Seems like it will work to me but I lack the experience of removing one of these phasers. What do ya think?

 

[mrrsm]

The means used to help keep the turnaround point at the bottom of the Crankshaft Cog of the Timing Chain on BOTH sides of BOTH TC sections in Hard Contact so that both Sprockets (if required) can be removed while the TC tension is being maintained is good and solid ...is academic. So as long as you can manage a satisfactory, non-destructive result... no matter how you achieve this effect with whatever creative means you decide upon using... will be very acceptable. 'All Roads... Lead to Rome...'

You MUST Maintain enough pressure and tension of the Passenger Side that has a Force Vector IN LINE WITH the Chain and Sprocket Line you will find great ...to Keep the Timing Chain Tensioner COMPRESSED. If you lose that Tension ...even for an instant.... the Spring Loaded Timing Chain Plunger will expand outwards and Ratchet Lock in the Expanded Position. If this happens... You will find Great Difficulty is reaching the Latch Release to relieve the lock and then wrangle to re-compress the Tensioner Rod and Foot-Pad in the very narrow spaces to work on this problem.

If you need some visual reference and proof of these issues... check out ALL of the related Albums on the Left Margin of my Photobucket here:

http://s557.photobucket.com/user/60dgrzbelow0/library/0000TRAILBLAZERENGINEREPAIR?sort=3&page=1

But...This will hold true ONLY if the means to do so do not involve securing to and relying upon ANY portion of the Timing Chain to either one or both Sprockets. It will work best if you can keep all of your manipulations of the Timing Chain strictly just enough to unbolt the Cam Phaser TTY Bolt (which MUST be replaced) and then immediately slide the Cam Phaser forward just enough to remove the Timing Chain... align the Black Link on the Arrow Line or Dot of the New Cam Phaser and then carefully slip the Phaser right back onto the nose of the Exhaust Camshaft Vertical Slot.

It might be necessary to relieve the pressure holding the Exhaust Camshaft rigidly in place and allow it to move just enough for the vertical "Mortise and Tennon" style alignment to take place without disturbing the Exhaust Valve Train. Keep using the process of Photo-Documentation for your Mechanic's Projects Image Library and Post the relevant ones as needed. You won't regret having a visual record and neither will the Members who may need to know how you did things in the future should they encounter similar problems and need your help. This Portion of Jack Crane's Multi-part Youtube Video Series of the R&R of the GM 4.2L Engine Head may prove helpful:

...and another video illustration of the complexity involved if the TCT literally "Goes Sideways...>":

 

[Goodfella]

"It might be necessary to relieve the pressure holding the Exhaust Camshaft rigidly in place and allow it to move just enough for the vertical "Mortise and Tennon" style alignment to take place without disturbing the Exhaust Valve Train."

Am I supposed th have the cam locked down? I am using service information from AC delco tech connect online and it makes no mention of this.
The procedure for complete timing replacment makes reference to a camshaft holding tool, but the one for just the phaser does not. Should i clamp something on the flats of the cam to ensure it does not move?

 

[Mooseman]

I didn't use a holding tool, just an adjustable wrench to hold the cam while loosening and tightening the phaser bolt. It's possible that the cam may need to be rotated very slightly to allow the phaser to slip back on.

How-to: Replace the Cam Phaser (aka: VVT Actuator)

 

[Goodfella]

Oh ok....i get it......thanks. im 99% sure all the noise was coming from the phaser........i will post pics of it compared to the new one but i can see damage for sure.

 

[mrrsm]

The Primary Reason for using the holding tool is to keep the spring tension held in the combined Valve Springs under tension from rotating suddenly and either injuring the Mechanic's Fingers or allowing the unrestrained Valves freed from the lack of the hold maintained by the presence of the Timing Chain locked in step with the Cam Phaser and Intake Sprocket from twisting suddenly and smacking the tops of any Pistons that might be close to Top Dead Center. @Mooseman has been fortunate to have avoided these problems.

You could also ensure that they will NOT move using Two Large Crescent Wrenches (... fitted tightly at the locations highlighted in Yellow on the Two Camshaft Hex Locations in the attached image below) and held in place using Pairs of Plastic Coated Wire Hangers... bent into the end circles of both Wrenches... and then fed through the holes in both Fender Panels... Rigid and Tight... to Free up your hands to work on the Cam Phaser and Timing Chain without fear of them getting loose and out of position.

 

[Goodfella]

As I'm preparing to replace these components, I have another question........is it ok to use standard high temp threadlocker? Or should i obtain the gm threadlocker listed on tech connect? I read some opinions online that say it is special and has antisieze properties that normal thread lock doesn't. I was really hoping to stop by auto parts store on my way home to get what i need but if the consensus is to use the gm product i will.

 

[Mooseman]

Hmmm. Had a look in the GM-SI procedure and it doesn't mention putting anything on the threads of the phaser bolt. Since mine dates back to 2009, the procedure may have been updated since then. Personally, I don't see the reasoning behind a threadlocker since it is TTY and has a fair amount of torque applied (18lbf + 135deg).

 

[Goodfella]

It is not mentioned in the procedure but the list of sealants lists the phaser bolt and has the part number 89021297

 

[Mooseman]

I might be wrong but there might be some threadlocker on the new bolt pre-applied.

That GM threadlocker just looks like regular red stuff. This one, which says ACDelco, has Permatex on it. even just the bottles are the same.
https://www.summitracing.com/int/parts/ado-10-1006/overview/

 

[Goodfella]

Phaser didnt come with the bolt! On my way to the stealership.

 

[Mooseman]

Figures. It did with the Dorman.

 

[Goodfella]

Made good progress last night. Got the valve cover and plugs and coils installed. The bailing wire trick worked really well keeping tension on timing chain. Hopefully I will get the rest back together tonight and see if my noise is gone. Fingers crossed.

 

[Goodfella]

Well after a grueling two days I finally got it back together. It started and idle came up very high. Oil pressure was in the 60 to 80 range on the mechanical gauge. Idle is erratic, check engine light came on. runs noticeably smoother but not right. Drove it to oriellys because I don't have a scanner. Had codes for MAF unexpected value, intake airflow something, idle higher than expected......blah,blah....... I was so exhausted and disgusted I didn't even write the codes down.....worst of all initially I heard the same sound! In park if I slowly bring the RPMS up it will make the noise, if you rev quick with more throttle its smooth and quiet. While driving it was quiet. I checked and rechecked all the electrical connections. After I scanned it I cleared codes and drove it home the check engine light never came on but was still not right. I would surge sometimes when RPMs were steady just about the same range where I heard the noise earlier.

 

[Mooseman]

Ah man, that really sucks. Almost sounds like my 9-7x with the 5.3. It has a knocking noise when I rev it but only between 1500 and 2800. While driving, only at part throttle in that same RPM range. Full throttle and at idle, no noise. It's been doing this for years but has been getting slowly worse. I also first thought it was something in the valvetrain so I replaced everything with non-DOD components. Didn't change a single thing. Someone suggested that it could be a piston wrist pin. It can't be a rod or main bearing as it would have self-destructed by now. I wonder if it could also be rod side play.

This truck is now mostly my winter beater and just waiting for it to throw a rod or piston but I still drive it like I stole it. It's too bad because I like this truck, good power and fun to drive along with the "that's a Saab?" comments. I've been letting it go and looks like a rust bucket now .

 

[limequat]

I feel your pain goodfella. I went through the same steps before I finally pulled my engine and found damaged/spun bearings. In my case the phaser WAS bad...but so were the bearings.

Have you considered sending an oil sample for analysis?

 

[Goodfella]

 

[limequat]

Yeah, we have aluminum bearings, not tri-metal.

My armchair quarterback analysis is that some relatively minor bearing damage was done when it was starved of oil. Might be worth trying to prolong the inevitable by switching to a higher weight oil, but the end is nigh.

Also, I'm not sure how you managed to submit this 10 days prior to my recommendation, but, if at all possible I would like to borrow your time machine.

 

[Redbeard]

Looking at my oil report from Blackstone labs the aluminum runs between a 4 and 5 with unit average of 4. And that's with 185,000 miles under it and 11,518 miles on this oil being tested.

 

[Mooseman]

Also, I'm not sure how you managed to submit this 10 days prior to my recommendation, but, if at all possible I would like to borrow your time machine.

I believe I had suggested this to him in another thread

 

[Goodfella]

I wish I had a time machine..........im getting rid of it.........buying new gmc today!

 

[Mooseman]

Well, do come back after and tell us about it. Sure you won't have anything to fix but we'd still like to hear about it

 

[limequat]

Bummer another one for the junkyard

 

[I_Shoot_Back]

These trucks deserve more commitment then they in general get. Aint too hard to replace the engine and she be good to go for a very long time again. Plz post this truck on kijiji or craigslist orwhatever you have around there so that some one can love that truck again.

 

[Mooseman]

Aint too hard to replace the engine

Have you actually done one of these? I have, never again unless the truck is really worth it. 2WD version notwithstanding.