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.***