New Guy on board

[rchalmers3]

Hello, my name is Rick, from just outside Columbia, SC. I hope you don't mind me joining your club!

I am semi-retired and am looking for a car hobby. I'm fascinated by these inline sixes, and have purchased a few different year model Trailblazers: nice cars with mechanical issues. That's my sweet spot, as I am incapable of performing satisfactory body/paint work!

I have a daughter who intends to be a licensed driver at years end. I have purchased a nice 2006 that has a rod knock. My aim is to pull the motor and have a look at the rod and crank bearings, then decide the best course of remedy. I have additionally purchased another Trailblazer at government auction. It's a 2005 with 125k on the clock. Dunno what I'll do with it at the moment. I may get the chassis and drive train ready to swap under a future (classic body) project, or the engine may simply be a donor for the daughter's 2006. Anyway, I am starting a collection around these vehicles and found this forum to use as a reference for consultation. Speaking of which... Here are a few beginners questions:

In looking for additional resources. Are their other places (websites, forums, ect.) I should know about that have information and active participation in LL8 discussions?

I have searched this forum and have created a (very) basic understanding of the various differences in the LL8 year models. Allow me to test my studies: At this time, my understanding is that the 2008 and 2009 engines are in their own category for swapping, due to the crank sensor and communications strategy. The 2004-2007 engines can be swapped at will, as long as the PCM corresponding to the installed engine is used. Does that sum things up?

I look forward to restoring some of these vehicles, possibly flipping a few just for fun and practice. I'm willing to share with you about anything I can, but I'm pretty sure most of you know more than I do, so I'll sign off with a thanks, and I look forward to hearing from you.

 

[Mooseman]

Welcome to our merry band. I'm sure you'll fit right in with your collection

In looking for additional resources. Are their other places (websites, forums, ect.) I should know about that have information and active participation in LL8 discussions?

There used to be the Vortec 4200 site but it went dark a couple of years ago when the owner passed away. We tried to copy some of the info here but nothing organized. Might be able to find some stuff from it through the Wayback Machine Internet Archive. We are fairly knowledgeable here on this engine. There's also TrailVoy but it's mostly tumbleweeds there now but we do use it for some archived info. Certainly not active there for sure.

At this time, my understanding is that the 2008 and 2009 engines are in their own category for swapping, due to the crank sensor and communications strategy. The 2004-2007 engines can be swapped at will, as long as the PCM corresponding to the installed engine is used. Does that sum things up?

Close. Plug and Play swapping can be done within 2002-2005 and 2006-2007. You could swap an older engine into an 06-07 by extending the coolant temp sensor wires and changing the coil plugs, so you could swap in the 05 engine into the 06. You wouldhave to keep your 07 PCM since it changed significantly that year.

If you have any questions, ask away.

 

[rchalmers3]

Hiya Mooseman, thanks for your prompt reply. All the way from Canada, eh? Hope you are having a pleasant and safe summer.

Thanks for mentioning those other resources. I found this forum in addition: https://www.inliners.org/ubbthreads/ubbthreads.php?ubb=postlist&Board=17&page=1

The activity there is not as robust, but there are some threads and discussions I found to be useful.
Hopefully I'll be able to learn these engines without being too much of a burden. I'll be traveling down to Myrtle Beach on Wednesday to pick up the auction truck. If I have troubles that I cannot figure out, I'll post up on this thread. Meanwhile...

Three questions about the fine points of the 2002-2005 to 2006-2007 differences:

On the 2006-2007 coolant temp sensor, does the sensor retain the previous plug configuration and pin out?

On the coil plugs, is it possible to fit 2006-2007 coils to the earlier engine, thus avoiding the need to modify the harness?

Lastly, please describe more about the specialness of the 2007 PCM. It was my understanding the 2006-2007 share the P12 and utilized CANBUS. Then in 2008 GM went with LAN networking, the 58x crank sensor update and other tidbits??? I am not challenging your knowledge, I'm refining my own understanding! As you have probably concluded, I'm old and find it hard to stuff new info into my addled brain. Please be patient while I formulate better questions!

Again, thanks in advance.
Rick

 

[TJBaker57]

was my understanding the 2006-2007 share the P12 and utilized CANBUS.

It is my understanding that CANBUS didn't happen in this platform until 2008. And even then only the PCM and TCM were on the CAN. This confirmed by @limequat I seem to remember. At least for the 4.2. I don't know about the 5.3.

My terminology might be somewhat off but I think before 2008 all communications were over single wire, class 2, SAEJ1850VPW. Now I might be mixing up hardware and protocols in that statement right there. As I have no formal education in the arena it is likely for me to come close to the mark but not a bullseye!!

 

[xavierny25]

Welcome to the Nation!

You've come to the right place for all things 360/370 Trailblazer related.

 

[Mooseman]

If I have troubles that I cannot figure out, I'll post up on this thread. Meanwhile...

If you could start a thread(s) in the appropriate technical section instead as this is more for intros than tech threads. Some people don't look at intro threads.

On the 2006-2007 coolant temp sensor, does the sensor retain the previous plug configuration and pin out?

AFAIK, yes. It moved from above the thermostat on the 05 to the back of the head on the 06.

On the coil plugs, is it possible to fit 2006-2007 coils to the earlier engine, thus avoiding the need to modify the harness?

No. They changed from a large teardrop shape to a small round shape along with the change in the valve cover and head.

Lastly, please describe more about the specialness of the 2007 PCM. It was my understanding the 2006-2007 share the P12 and utilized CANBUS. Then in 2008 GM went with LAN networking, the 58x crank sensor update and other tidbits???

These threads from the FAQ pretty much explains the differences:
4.2L interchangeability by years
4.2L Incompatibility by years ('04 engine in '08 truck, no start)
'06 4.2 swap into an '05

 

[rchalmers3]

Thanks TJ, I also don't have a fundamental understanding at the moment. For now, I'll go with the idea that 2008 plus engines require like kind replacements.

 

[rchalmers3]

Thanks Mooseman, I had reviewed those threads and will continue to reference them as needed. With a little more tme and hands on experience, I expect to have a better understanding of the fundamentals of the LL8 development.

I have another question about these motors: Why do you think it is that the LL8 seems to suffer from rod bearing failure much more than say, LSx engines of similar age and mileage? I notice that half the cheap cars on Facebook marketplace have bad engines. The other half suffer from bad 4L60's, but that is no surprise given the mileage! My 2005 Serra 1500 has 360k on the 4.8L in comparison.

Thank you,
Rick

 

[mrrsm]

Welcome Aboard. Can’t wait to see as much of your work as possible memorialized with images and read about your progress as you go forth! If you need Tear Down and Re-Build information on the Re-Build GM Atlas Vortec 4200 4.2L Engine for Parts and Part Numbers and Specialty Tools as well as deconstruction and Clean Up imagery, please visit my links here:

For actual Engine Work:

https://gmtnation.com/forums/threads/the-85-000-00-gm-4-2l-engine-repair.14423/

https://gmtnation.com/forums/threads/engine-swap-2004-for-2002-gm-atlas-4-2l-motor.15786/

For Engine Imagery, Parts & Tools, please visit my “Flickr-Bucket” (...most are located towards the bottom of the Albums Page):

https://www.flickr.com/photos/126111508@N07/albums

Regarding your Question about Connecting Rod Failures on the LL8 Engines:

I’ve not witnessed any Mains-Crankshaft Bearing Failure. Quite the contrary, the bearings on an engine with around the same mileage as yours looked positively pristine showing very low bearing surface wear. The “Rod Knocking” sounds are more likely being caused by “Piston Slap” due to excessive Piston to Cylinder wear caused by the Carbon Build-Up on the Compression Rings sticking tight to the inner Piston Grooves.

Poor Maintenance and lack of frequent enough Oil Changes using Organic Motor Oil instaead of HQ Synthetic Oil is usually what spells the demise of these Motors. The Cylinders walls on your engines will probably display some oval scarring in the upper 1/3 areas due to this problem with loss of the Graphite skirt coatings and deep scarring on the Pistons as a result. The Cylinders Sleeves in the GM 4.2L Engines have only 1.5mm of wall thickness and if you find them out of specs… they will deserve replacement using Melling Sleeves. The Tools used and the more intimate specifications and procedures to follow are covered on Page 5 in the Engine-Swap link above.

Best of Luck!

 

[Mooseman]

My '02 had a spun bearing when I bought it however it was poorly maintained. We have heard of a few getting rod knock but it's not a lot. The majority of these trucks die from other issues, like mine when the tranny went but the body was just too rusted. Saying that these engines suffer from bottom end issues would be incorrect IMHO.

The LS 5.3 in my Saab on the other hand does make some noise, however I think it's continuous piston slap. Been doing it for years.

 

[rchalmers3]

Mr.RSM and Mooseman,

Thank you both for sharing your observations. When browsing Facebook Marketplace, half the offers in my price target range (cheap!) mention rod knock or bad engine. But those reports are from their owners, who may not know the true source of the engine noise or why it locked up. Thanks to you guys I will be better prepared for a wider range of diagnosis as to why the engines I come across have failed.

BTW, the 2006 engine starts, runs and maintains slightly over 40PSI oil pressure indicated at idle. It knocks on slight revving and sometimes stalls at idle. No CEL. no codes after a battery replacement. I have not observed the PCM I/O's in order to diagnose the stall. My lazy mind attributed it to a sudden resistance to engine rotation. I have not done any further looking into it, as I plan on seeing what the other car needs first. Then I'll decide if the 2006 gets a swap or refurbishment of the engine.

More later,
Rck

 

[Mooseman]

The oil pressure gauge is fake.
Trailblazer oil pressure gauge doesn't tell you the oil pressure (4.2L engines) (YouTube)

As long as you have a minimum 12 psi, it will keep showing the fake readings.

 

[rchalmers3]

Yep, that's why I mentioned the indicated pressure. 'll go read up on where to tap in a mechanical gauge.

Thanks Mooseman,
Rick

 

[mrrsm]

Symptomatically... If the Connecting Rod(s) gets loose due to Failed Con-Rod Bearing(s)... .it will knock LOUDEST at Idle...and the sound will DECREASE in volume and frequency as the Engine RPM is raised. The reverse may occur with Piston Slap events.

According to the GM OEM Trailblazer Manual... The correct Range of Oil Pressure should be between 12 PSI at Idle and around 65 PSI at around 2,000 + RPM before the Gerotor Oil Pump By-Pass Valve engages:

@MAY03LT has Three Definitive Videos that will short cut your path to installing an Analog Oil Pressure Gauge and get more realistic results in all RPM Ranges.

 

[rchalmers3]

I watched those suggested videos, plus a few more. One YouTuber had an Envoy that had very low oil pressure after a 30 minute drive. He was monitoring the pressure with a mechanical gauge. The engine only produced 4-5psi at idle, causing the dash gauge to flicker and drop to zero, and triggering the CEL and low pressure warning.

Strange thing: if he shut off the engine for a few seconds, then restarted it, the idle oil pressure returned to a stable 11 psi. That makes me wonder if there is something else going on. A couple of thoughts would be a shifting big end or crank bearing. Another would be the exhaust cam advance mechanism. Is this a known issue with an understanding of the causes?

Guys, I'm a slow, suffering hunt and peck typist, so if my posts are brief and incomplete, please understand that I prefer an economy of time at the keyboard. Also, the EYE key on my laptop must have a bread crumb trapped under it. I must correct for missing eyes (ha! Not gonna type that letter) all the time. Bear with me, please.

Edit: another possibility for low pressure could be an air leak on the pickup side of the oil pump??
Rick

 

[Mooseman]

Edit: another possibility for low pressure could be an air leak on the pickup side of the oil pump??

It's possible, just like on the LS engines. The early production had a tech bulletin on defective o-rings. Also possible is a blocked pickup.

 

[fletch09]

Welcome

 

[mrrsm]

In addition to the Screen Pick-Up Tube Blockage Issue is the technical failure of the First GM Atlas 4.2L Front Cover-Gerotor Oil Pump design where the "BLUE" Viton "O" Ring was getting nicked during GM Factory Assembly or just flattening out so badly that later on... the Gerotor Gears were cavitating from a loss of Suction at the juncture between the Oil Pick-Up Tube and the Base of the Gerotor Oil Pump. The drop in Oil Pressure at highway speeds could be catastrophic to the motor.

GM responded with a New Design that solved the issue. The link below will take you to my "Flickr-Bucket" where you can see the differences between these designs. You cannot Mix & Match the two different "O" Rings and Gerotor Oil Pumps.They must be selected as a matched set between The Oil Pick Up Tube, The "BLUE" Sealing "O" Ring or the "ORANGE" Grommet and likewise the correct Gerotor Oil Pump fastened to the Timing Cover via a series of 10.9 Torx Scews:

I just freshened up my "Flickr-Bucket" Gerotor Oil Pump Album, so these 65 photos should show the differences mentioned above... quite nicely:

GM Atlas 4.2L LL8 Engine Gerotor Oil Pump

This Album shows Images of the Autopsy of a Late Model GM 4.2L LL8 Gerotor Oil Pump.

www.flickr.com

 

[rchalmers3]

Mr. RSM,

I'm wondering: Is the newer design recommended as an important upgrade the previous design, or can the blue o-ring be replaced, thus restoring a positive seal? What is your preference?

Rick

 

[gmcman]

Welcome aboard

 

[mrrsm]

Yes... The Updated Design is my personal choice because it has proven More Mechanically ROBUST in it's configuration based upon these distinctions:

(1) The Updated Oil Pick-Up Tube Flange Pipe is LONGER and thus is less inclined to bend or gyrate around under heavy Engine Vibrations. Unfortunately, the 2002-2003 OEM Gerotor Oil Pump Flange was made with a Very Shallow Port and a combination of having a Beveled inlay along with a "dimple" expansion in the Much Shorter Pick Up Tube Insert point present in Early Design of the Gerotor Oil Pump.

(2) Apparently, the Chief Designer (Ron Kociba) and his late 1990s GM Atlas LL8 Engineering Team decided they could ensure a Vacuum Seal with this First Pump by simply "squeezing down" the "BLUE" Viton "O" Ring and securing it Off Angle with a Single Flange fastener. Nope. Too Risky. Once that "O" Ring Flattens Out or is compromised by an inadequate installation...All Bets Are OFF.

(3) If you want a real World Example of how this failure can happen... Take a Drinking Straw and about 3" below the end of it...use a Razor and make a tiny slit in it. Then drop its length into a Glass of Water (with the tiny slit above the Water Line) and just try to take a sip... Keep Trying... and you'll get the right idea.

(4) The Problem gets even more exacerbated if you pull out the Straw from the Water Glass ...and Plug Up the end of it with your finger. The very same thing happens inside the Motor when the Oil Pump Pick Up Tube get completely occluded with Gas Gummed-Oily Crap....and then tries to get around the blockage, possibly by entering through a compromised Flange vacuum Seal and allowing Air into the Oil Stream.

(5) Since "Nature HATES a Vacuum" a Torn, Nicked or Flattened "BLUE" "O" Ring is more likely to fail on HIGH MILEAGE ENGINES. Once Compressible Air migrates into the Gerotor Oil Pump... Bye-Bye 65 MAX PSI Oil Pressure... and so...Good Bye Engine Bearings.

A Brand New "BLUE" "O" Ring WILL suffice in lieu of the COMPLETE Replacement of the Front Timing Cover and Updated Gerotor Oil Pump for around $135.00 via gmpartsdirect.com (Plus another $30.00 or so for the Updated Melling Oil Pick Up Tube with "ORANGE" Grommet. But if I have to go this Deep into any Engine... I follow General George S. Patton's Philosophy:

"I NEVER want to Fight for the Same Ground...TWICE."

 

[rchalmers3]

A quick update, I have confirmed the 2006 engine is suffering from loose big end bearings on cylinders #2 and #4. I have my fingers crossed that the crank and block will be usable.

The 2005 auction vehicle was a bust. Literally. It has the optional ventilated block in the passenger side area of #1 rod. Besides the broken rod, there are other loose rod bearings and uneven compression readings. Only #6 cylinder is healthy. I started pulling the 2005 motor and trans for repairs. It will give me practice for getting the 2006 out efficiently. I made a good start on the 2005 today. I ordered a 36mm deep socket for the axles and should have the engine out on Tuesday.

 

[rchalmers3]

Mooseman, I'm willing to post up new threads with images on these engine projects. Can you suggest the appropriate forum?

Thank you,
Rick

 

[Mooseman]

Right here in the 4.2 Vortec section. That would be awesome.

Why can't some of these auctions actually say if it's running or not?!? Well at least you'll have some spare parts.

 

[mrrsm]

Remember that once you pull the Motor and get it mounted on the Engine Stand, you can expect that quite a lot of the M11 X 2.00 TTY H-10 HEX Head Bolts AND the Crankshaft M10 X 1.50 TTY Main Cap-Screws WILL Snap Off during their removal with uncustomary ease. And thus, you will require either a Hook Pick Set or a Reverse HSS Drill & EZ-Out Carbide Quality Combo Bolt Extraction Kit to remove all of the remaining Bolt Remnants.

Make certain to Completely Remove the Engine Head from the Block PRIOR to attempting to Extract Bolt remnants... Or You'll wind up "Wishing Your Father NEVER met Your Mother" for all of the aggravation you'll otherwise have to deal with when doing this part of the job as a 'Necessary Evil'.

Take Great Care with the GM Atlas LL8 Engine Mains Buttress areas, as they sport Blind Bolt Holes that are threaded down into the Soft Aluminum to about 50mm below the top of the submerged 13.25mm X 18mm long Hollow Guide Pins that center the 7 Steel Mains Caps and Crankshaft Bearing Halves over their matiing in-block counterparts. If you discover that any of these Threaded Bolt Holes suffer from having any Internal Damage... Do Not Despair.

Shortly, I'll be posting a Write Up on How to Perform the TIME-SERT Repair of the GM Atlas Engine Mains Using 40mm M10 X 1.50 Internally Threaded Steel Cylinder Inserts.

THIS job becomes easier to accomplish using a clever combination of the TIME-SERT M10 X 1.50 Mains Kit meant for the Cadillac V6 Engines, along with a 12" long X 13/32" Aircraft Radial Engine Cobalt Drill Bit held in line with the Mains Bolt Holes using an Aluminum Drill Guide Plate of my own Design.

Using these Tools in combination will ensure that all (14) Threaded Holes can be perfectly repaired ...if you deem this necessary.

The Replacement Crankshaft Mains Bolt Set needs to be (14) GM Part# 11571239 (UPDATED INFORMATION ON 07/20/2020
GM Part# 11569841) and may be very hard to find right now. eBay is a very good place for you to start checking with the various GM Dealerships to purchase them in Ones and Twos, here and there for anywhere from around $5.00 to $51.00. So it will be well worth getting an early start to find them, as ALL of the ones presently inside the Motor will have to replaced. This is the Flanged Bolt Design you want:



I would only choose to use the Dorman flavor of these Crankshaft Mains Bolts as a Last Ditch Effort as they have Free Moving Trapped Washers in their design and thus, may behave (or misbehave) differently when being Installed, Torqued and then Tightened down to their Final TTY Stretched Condition:

 

[mrrsm]

THIS Updated Information describes a Better Part# for the GM 4.2L LL8 Crankshaft Mains Bolts:

GM Part# 11569841

However...as these individual GM Bolts can be Pricey and Scarce… as an Alternative Source...You might consider the Better Price & Availability and Full Compatibility of THIS eBay Offer from APDTY Part# 114276 @ $51.59 per (10) Bolt Set. You will need Two of these 10 Bolt Sets as a Total of (14) New TTY Mains Bolts are required...This eBay Offer shows (4) Sets are still available:

http://rover.ebay.com/rover/1/711-5...0001&campid=5338077216&icep_item=353048274711

 

[rchalmers3]

May I share my impulsiveness and stupidity with you?

The Trailblazer I bought for the daughter is a 2008 model. I'm completely happy with that.

The driver door on her car has apparently been replaced. It is color matched and has a 2006 decal, with a corresponding 2006 VIN. Obviously it's a different VIN than what is on the car and the title. I didn't make that observation until.....

I used the door decal for reference, bought a core engine and started a thread on repairing the 2006 replacement engine, which definitely has a 7x notched crank throw.

Looks like I'll need to locate another (58x) donor motor for her car.

Told ya I was getting old.

Rick

 

[m.mcmillen]

It would be significantly cheaper to buy the bolts here:

2002-2012 GM M10x133.5 Multi-Purpose Bolt 11569841 | GMPartsDirect.com

2002-2012 GM part # 11569841 - M10x133.5 Multi-Purpose Bolt

www.gmpartsdirect.com

You will also need connecting rod bolts as they are TTY also. 12552947 is the part number for those.

 

[mrrsm]

I wonder what they are charging for S&H... I got nailed on getting a few of these from a few Dealerships Sellers that charged more for that than for the Price of The Fastener(s).

And speaking of... That APDTY Company is just a few hundred miles from me in Florida, so I thought I'd Kill 2 Birds with 1 Stone by throwing them some business AND getting the chance to Test their Fasteners Out in a Block of Aluminum (NOT in an Aluminum Engine BLOCK) while using a few Extra 40mm Long TIME-SERT Inserts and see how the Bolts behave going into the Inserts via this "Steel On Steel" event..

I'll set the stage for this by ensuring that the interior Threads of the SERTS AND the Thread Lines on the New APDTY Bolts are BOTH Clean and Dry. Then I'll do a Photo-Play on this Experiment over in the "TIME-SERT 101" Article ...Warts and All.

With all that said, we should be able to see what happens after I follow the Instructions from the GM OEM Installation Specs. I'll try to discover what their reactions are going to be when going in and when subsequently being unwound after they all cool to ambient temperature to see if any break when used within the TIME-SERT System.

These Fasteners shipped FAST in Two APDTY Company Boxes ...and By God... They even Silk Screened the Bolt Heads as being "10.9" Metric Hardness. I thought that was Pretty Impressive... Now let's see how well they actually WORK to ensure they are 'Not Just Another Pretty Face'. The only thing I have not confirmed as yet is whether or not the TTY Factory Bolts are ALSO 10.9 Metric Hard. So "Mac",,, if YOU know, please edify us all about it. Here are some images of what these look like:

 

[m.mcmillen]

I wonder what they are charging for S&H

$24 to Wisconsin

 

[mrrsm]

Dammit Mac... Sorry... Even though there was No In State Shipping & Handling Charges on this... I should've included the Damned Receipt to show the State Tax included for the Honest TCO and Per Bolt Price for all 20 TTY Bolts:

 

[rchalmers3]

Thanks guys, I will get the OEM hardware from the lowest cost source I can find.

I'm going to need to replace the two tubes that locate the head on the block. Anyone have easy access to part numbers? Better yet, what do you guys use for getting OEM part numbers and prices? Besides a visit to the dealer that is.

 

[m.mcmillen]

I have a wholesale account and login through my local dealer and can get pricing and availability.

The part number is 3522352

 

[rchalmers3]

I have a wholesale account and login through my local dealer and can get pricing and availability.

The part number is 3522352

Thanks for the part number. While I would appreciate the access and discount. I'm not in a position to apply for an account at the local dealer. What's a hack like me to do, other than to post up here?!

 

[m.mcmillen]

That’s what we’re here for.

 

[rchalmers3]

For the entire set of TTY bolts and the two locating pins, the GM Parts Direct price, with shipping is $254. The Chevrolet Parts Online price is $70 more.

 

[Mooseman]

So as to not mix up the threads and avoid confusion, this one is locked.