2010 DENALI 6.2 Motor "Seized"

[dyce51]

Picked up a 2010 Denali with a 6.2L I believe L94 very cheap. Was told motor was seized and my plan was to just swap a 6.0 into the truck. Previous owner said he was told that it was a lifter seized up. Story was that he started it in his driveway, it ran for 10 seconds and just shut off. Was "locked up" after that. Body is in Great shape and and transmission was rebuilt less than 100k Miles ago. Everything else had extensive service history every 3-5k miles with recommended maintenances done at specified intervals.

Anyway...motor is not original and was replaced about 50K Miles ago with a used unit...supposedly a "Low Mile" motor. Don't have any proof of this. Get the truck home, motor turns less than 1 revolution back and forth. Initial thought was maybe timing chain let go...but I was able to see rocker movement through the oil fill hole in the valve cover in the movement I am able to get out of the crank. Motor was not low on oil, and wasn't overheated.

Plan to pull valve covers at some point, but just getting some "feelers" from others on the forum. How common is it for a lifter to seize in the bore on one of these blocks? I've worked on a lot of the older "SBC" era stuff, but haven't touched much of the newer LS motors. I have no problem digging into it, assuming it's salvageable.

Again, bought it with intent to replace the motor, but if it's something I would be able to fix...that would be cool too!

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

 

[dyce51]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

Here's a couple pictures! Black interior as well. Few minor things to take care of too with time. Also have a 2013 SLT (Yukon), but not an XL. We have found with 4 kids, really wanted the extra room, love the style of these rigs, and the 2013 has been VERY good to us!

Thank you for the Welcome!

 

[Marky Dissod]

How common is it for a lifter to seize in the bore on one of these blocks?
I've worked on a lot of the older "SBC" era stuff, but haven't touched much of the newer LS motors.
I have no problem digging into it, assuming it's salvageable.

Again, bought it with intent to replace the motor, but if it's something I would be able to fix ... that would be cool too!

When you say, 'a lifter', there's two kinds of lifters in GM LStype V8s capable of V4 mode:
one mode lifters (ol' school), and two-mode lifters that allow V4 mode to happen.

Two mode lifters cannot possibly last as long as one mode lifters, even with the most responsible oil change intervals.
Two mode lifters fail often enough, that:
the majority of engine rebuilds replace them with one mode lifters, either as precaution or as a fix
fixing / replacing one or more failed lifters is among the most common reasons to rebuild these engines
Many rebuilt engine vendors sell more engines lacking V4 mode than having it, because it improves longevity and durability

 

[dyce51]

When you say, 'a lifter', there's two kinds of lifters in GM LStype V8s capable of V4 mode:
one mode lifters (ol' school), and two-mode lifters that allow V4 mode to happen.

Two mode lifters cannot possibly last as long as one mode lifters, even with the most responsible oil change intervals.
Two mode lifters fail often enough, that:
the majority of engine rebuilds replace them with one mode lifters, either as precaution or as a fix
fixing / replacing one or more failed lifters is among the most common reasons to rebuild these engines
Many rebuilt engine vendors sell more engines lacking V4 mode than having it, because it improves longevity and durability

I am familiar with the 2 different types of lifters in these motors...I'm more curious if either the DOD or Non DOD lifters actually get "Stuck" in the blocks of these 6.2L motors often, or if I should be looking elsewhere...I will probably end up pulling valve covers first to see what I can see. I haven't been able to get it into the shop yet, just researching before hand is all.

 

[Foggy]

The lifters "can" get stuck.. But if it only rotates several degrees in
either direction then you have a broken piston or rod more than likely
hanging up the "rotating assembly"
I haven't seen a dod lifter stick and keep the motor from turning
Unless it took out several lifters and the camshaft and those pieces have dropped
into the crank/rods area

 

[dyce51]

The lifters "can" get stuck.. But if it only rotates several degrees in
either direction then you have a broken piston or rod more than likely
hanging up the "rotating assembly"
I haven't seen a dod lifter stick and keep the motor from turning
Unless it took out several lifters and the camshaft and those pieces have dropped
into the crank/rods area

That was my initial thought was in rotating assembly. I'll probably start at valve covers but most likely assume I will be pulling the pan to have a look and dropping in a motor I just ran back out with my ratchet and socket to get a better idea of movement...and I get a full 3/4 of a rotation from stop point to stop point.

 

[j91z28d1]

definitely pull the valve covers.. only thing I can think of that would stop an engine from moving valve train wise would be a valve hitting a piston? either from dropping or maybe a valve seat fell out.

 

[dyce51]

definitely pull the valve covers.. only thing I can think of that would stop an engine from moving valve train wise would be a valve hitting a piston? either from dropping or maybe a valve seat fell out.

I was pretty sure it had a busted timing chain until I was able to see rocker arm movement through the oil fill hole in the valve cover...but I suppose it could have jumped...

I'll start up top and go from there! As stated in Original Post, I had intentions of pulling the motor...but if it's not toast I will attempt to fix.

Thanks for the input guys, and look forward to being on the forum!

 

[Rokjhn]

I picked up a 2009 Denali In similar condition scenario. Pulled oil plug and coolant came out with the oil. Couldn’t turn motor over with breaker bar on crankshaft pulley. Had to pull engine with transmission together. Pulled the heads and here is what I found, looks like the piston exploded. Taking block to machine shop to assess, but think it can be rebuilt. **Update-looks like a valve seat came loose and caused the piston to implode.***

 

[dyce51]

I picked up a 2009 Denali In similar condition scenario. Pulled oil plug and coolant came out with the oil. Couldn’t turn motor over with breaker bar on crankshaft pulley. Had to pull engine with transmission together. Pulled the heads and here is what I found, looks like the piston exploded. Taking block to machine shop to assess, but think it can be rebuilt.

That looks rough! I haven't drained the oil but the oil is at the "full" mark with no signs of water. I'm pretty curious what I have going on though...if I do have to pull the motor, I would probably rebuild at some point and swap it into something.

 

[Geotrash]

I was pretty sure it had a busted timing chain until I was able to see rocker arm movement through the oil fill hole in the valve cover...but I suppose it could have jumped...

I'll start up top and go from there! As stated in Original Post, I had intentions of pulling the motor...but if it's not toast I will attempt to fix.

Thanks for the input guys, and look forward to being on the forum!

Yup. Start by pulling the heads.

 

[ejf2461]

Picked up a 2010 Denali with a 6.2L I believe L94 very cheap. Was told motor was seized and my plan was to just swap a 6.0 into the truck. Previous owner said he was told that it was a lifter seized up. Story was that he started it in his driveway, it ran for 10 seconds and just shut off. Was "locked up" after that. Body is in Great shape and and transmission was rebuilt less than 100k Miles ago. Everything else had extensive service history every 3-5k miles with recommended maintenances done at specified intervals.

Anyway...motor is not original and was replaced about 50K Miles ago with a used unit...supposedly a "Low Mile" motor. Don't have any proof of this. Get the truck home, motor turns less than 1 revolution back and forth. Initial thought was maybe timing chain let go...but I was able to see rocker movement through the oil fill hole in the valve cover in the movement I am able to get out of the crank. Motor was not low on oil, and wasn't overheated.

Plan to pull valve covers at some point, but just getting some "feelers" from others on the forum. How common is it for a lifter to seize in the bore on one of these blocks? I've worked on a lot of the older "SBC" era stuff, but haven't touched much of the newer LS motors. I have no problem digging into it, assuming it's salvageable.

Again, bought it with intent to replace the motor, but if it's something I would be able to fix...that would be cool too!

Sir, Save youself some time and headache. Buy a new gm LS3 crate long block. Put your intake and injectors on it and take it to a local tuner do have a tune installed. You wont have to deal with afm/dod problems ever again or direct injection. I am a police chief and have several Tahoes and Caprices and every single one of the them have had lifter issues and then runined the camshaft lobes. After installed 3 engines in 1 Tahoe I said enough and started installing LS3 crate motors. You can save few bucks by rebuilding what your have but finding great machine shops nowadays isn't easy! Good Luck

 

[Marky Dissod]

Sir, Save youself some time and headache. Buy a new gm LS3 crate long block.
Put your intake and injectors on it and take it to a local tuner do have a tune installed.
You wont have to deal with afm/dod problems ever again or direct injection.
I am a police chief and have several Tahoes and Caprices and every single one of the them have had lifter issues and then runined the camshaft lobes.
After installed 3 engines in 1 Tahoe I said enough and started installing LS3 crate motors.
You can save few bucks by rebuilding what your have but finding great machine shops nowadays isn't easy! Good Luck

How do we get this post stickied? AWESOME.

 

[hagar]

Pull your spark plugs and turn the engine over by hand. I have seen it before that a head gasket went and filled a cylinder with coolant. The engine would turn over part way in both directions before locking up, exactly like yours. I actually thought the engine had a broken crank or rod or something so I pulled it out. I Caused myself a whole bunch of extra work, could have just popped the head and changed the gasket.

 

[Geotrash]

Sir, Save youself some time and headache. Buy a new gm LS3 crate long block. Put your intake and injectors on it and take it to a local tuner do have a tune installed. You wont have to deal with afm/dod problems ever again or direct injection. I am a police chief and have several Tahoes and Caprices and every single one of the them have had lifter issues and then runined the camshaft lobes. After installed 3 engines in 1 Tahoe I said enough and started installing LS3 crate motors. You can save few bucks by rebuilding what your have but finding great machine shops nowadays isn't easy! Good Luck

Good advice, especially if you have a departmental budget to work with.

On the shoestring "thousandaire" budget that many folks are working with (either real or spouse-imposed), doing some diagnostics and relatively inexpensive repairs, may need to be step 1, by necessity.

 

[dyce51]

Thanks for the advice guys...I bought this as a "Project" to get into an XL cheap. The current short Yukon we have just doesn't have enough room for all our "Crap" when taking the whole family overnight somewhere, or throwing in a stroller with all 4 kids along... A new crate motor would cost more than I bought the rig for. If it doesn't pan out, I'll end up parting it out. My plan was to pull the plugs first and then move on to valve covers and go from there. Plan on tearing into it in the next week. I'll update the post as I go!

 

[Marky Dissod]

Sir,
...
I am a police chief and have several Tahoes and Caprices.
Every single one of the them have had (dual-mode) lifter issues, and then ruined the camshaft lobes.
After installed 3 engines in 1 Tahoe I said enough and started installing LS3 crate motors.

May have something to do with an inordinate amount of time idling, peppered with assertive / enthusiastic driving.
Two-mode lifters especially don't deal well with quick transitions from V4 mode to high RpMs.

Plus it's pretty clever to upgrade from an L94 to an LS3 - an extra 30 horses & 15ftlb, no V4 mode, no VVT.

 

[dyce51]

Well, pulled spark plugs last night, thinking it dropped a valve...

 

[dyce51]

Another update for everyone interested. Pulled valve cover and nothing looked odd, loosened rockers on that cylinder and nothing seemed odd there. Threw my leakdown tester on that cylinder and I'm getting air out the intake only, so fingers crossed piston is intact and it's a head/valve issue yet...and the piston didn't get the piss beat out of it!

Next couple weeks I'll get the coolant drained and start tearing apart and pull the head!