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Discussion Starter · #21 ·
It will be difficult for you without knowing all of the right questions to ask, to firmly indicate they charged you by the labor manual, but they did not service your car by the repair manual. Bent valves are ruled in, or out before the timing chain and then actuator install. If they are being truthful about the actuator install sequence, clearly someone messed up, as that's a lot of work to have been avoided and replacing four actuators using the special tool for the process means four chances to have accidentally installed one out of timing.

Not every repair needs to have the book open, but a reasonably sufficient diagnostic approach should be followed to avoid situations like this. This is an interference engine, and misfires over one bank and a timing code would have definitely had me reaching for my compression tester and or listening to the intake ports at the throttle body on all 3 hand cranked compression strokes for the sound of leaking valves.

Form an opinion on what you think may have happened. I'd ask why the car no longer runs given you drove it there and the components should have made it better. If they say it stopped running shortly after you dropped it off, or didn't run after the timing chains were installed, ask how they knew it needed actuators if it didn't run. Then decide whether or not you need to state what you believe may have happened.
Thanks, appreciate the great feedback.
 

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Discussion Starter · #22 ·
Thanks, appreciate the great feedback.
This is the reason the dealer is telling me I need an engine. After replacing the timing chain, the issue was still the same and so they went ahead and changed the actuators on bank 2 cams, still same issue. They thought they got bad actuators and replaced them again with no results. A Cadillac field engineer, according to the dealer, got involved and diagnosed that the actuators were not parking during idle, causing the misfiring and eventual stall. This can be caused by not enough oil pressure getting to the actuators, thus the new head scenario or new engine. I asked them, if it could be the oil pump, but they said no.
Does this make sense to you guys… I’m not real sure how these actuators work, but needing an engine, because an actuator is not getting enough oil pressure, seems a little extreme. Like I said, I don’t know exactly how these actuators work.
Any thoughts?
Thks again guys, appreciate all the great feedback I’ve been getting.
JH
 

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There's a big difference between needing a new engine and needing a new head.
 

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Discussion Starter · #24 ·
There's a big difference between needing a new engine and needing a new head.
Yes there is, but not in price, in warranty, 90 days for repaired head or 3 years 100,000 miles for re-manufactured engine.
 

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Yes there is, but not in price, in warranty, 90 days for repaired head or 3 years 100,000 miles for re-manufactured engine.
Uh, there should be a big difference in price as well.

They quoted you 8 G's for a new engine.
What's the quote for a new head?
 

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Discussion Starter · #26 ·
Uh, there should be a big difference in price as well.

They quoted you 8 G's for a new engine.
What's the quote for a new head?
5Gs, but very little warranty, which to me, is not worth the savings.
 

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You didn't run with loose timing chains long enough to skip time and bend the valves, did you? I think that is they key thing to determine. Although if the valves were bent when you brought the car in, they shouldn't have advised you to replace the chains. If they were bent during/after the repairs, obviously the dealer's fault.

I tend to agree on replacing the whole engine vs. replacing a head on a high-mileage motor. Good luck with your car disaster, it happens to all of us eventually.
 

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This is the reason the dealer is telling me I need an engine. After replacing the timing chain, the issue was still the same and so they went ahead and changed the actuators on bank 2 cams, still same issue. They thought they got bad actuators and replaced them again with no results. A Cadillac field engineer, according to the dealer, got involved and diagnosed that the actuators were not parking during idle, causing the misfiring and eventual stall. This can be caused by not enough oil pressure getting to the actuators,
I'm knowledgeable, but not an expert and that doesn't sound right. It sounds like they are mixing the actuator function up with the LGX 3.6L actuator function. The LGX has an intermediate actuator park position, all others are parked at full stop by default at idle, unless the computer commands advance, which it does immediately upon start up for a few seconds until idle speed sets in.

Doesn't appear much diagnosing went on with two actuator set swaps, and what happened to that gap. $5k to swap out a cylinder head because they missed it, take it somewhere else, I wouldn't let them work on it anymore for money.
 

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5Gs, but very little warranty, which to me, is not worth the savings.
That sounds waaaaaaay steep for a head replacement.
It's almost as if they're attempting to steer you and cover their tracks....


Nah. A dealership would never do that. ;)
 

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Discussion Starter · #31 ·
That sounds waaaaaaay steep for a head replacement.
It's almost as if they're attempting to steer you and cover their tracks....


Nah. A dealership would never do that. ;)
Haha… I think they just don’t know exactly what the issue is and the safe way to deal with it, is to replace the engine.
 

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Discussion Starter · #32 ·
I'm knowledgeable, but not an expert and that doesn't sound right. It sounds like they are mixing the actuator function up with the LGX 3.6L actuator function. The LGX has an intermediate actuator park position, all others are parked at full stop by default at idle, unless the computer commands advance, which it does immediately upon start up for a few seconds until idle speed sets in.

Doesn't appear much diagnosing went on with two actuator set swaps, and what happened to that gap. $5k to swap out a cylinder head because they missed it, take it somewhere else, I wouldn't let them work on it anymore for money.
I’m just regurgitating what the service advisor told me, which doesn’t mean much, since he seems to stutter when I ask specific questions.
 

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Discussion Starter · #34 ·
You didn't run with loose timing chains long enough to skip time and bend the valves, did you? I think that is they key thing to determine. Although if the valves were bent when you brought the car in, they shouldn't have advised you to replace the chains. If they were bent during/after the repairs, obviously the dealer's fault.

I tend to agree on replacing the whole engine vs. replacing a head on a high-mileage motor. Good luck with your car disaster, it happens to all of us eventually.
As I understand the 2008 DI engine is a non- interference engine, which, I think, will not bend the valves or damage the cylinders, if the chain breaks or stretches. Nevertheless, they would not have replaced the chains and or the actuators if the engine had any strange knocking noises. At higher rpm’s (>2K) the engine, although misfiring on bank 2 only, ran half way decent and that’s how I drove it to the dealer.
 

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As I understand the 2008 DI engine is a non- interference engine, which, I think, will not bend the valves or damage the cylinders, if the chain breaks or stretches. Nevertheless, they would not have replaced the chains and or the actuators if the engine had any strange knocking noises. At higher rpm’s (>2K) the engine, although misfiring on bank 2 only, ran half way decent and that’s how I drove it to the dealer.
The 2008 3.6 LY7 is not diect injected.
The 2008 3.6 LLT is direct injected and IS an interference engine.

Which do you have?
 

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At higher rpm’s (>2K) the engine, although misfiring on bank 2 only, ran half way decent and that’s how I drove it to the dealer.
That is not a sign of timing chain health. As to whether damage had already occurred before you took the car in, I have no idea. And if it had, a meticulous and excellent mechanic would have checked first. It wouldn't be the first time an obvious, needed repair has been made to an engine that had other problems as well.
 

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Discussion Starter · #39 ·
That is not a sign of timing chain health. As to whether damage had already occurred before you took the car in, I have no idea. And if it had, a meticulous and excellent mechanic would have checked first. It wouldn't be the first time an obvious, needed repair has been made to an engine that had other problems as well.
Well, don’t know either, but they replaced the timing chain and had to start it to realize that the actuators may be bad also and took it apart again to replace the actuators and than diagnosed it as the actuators not locking during idle, due to lack of oil pressure. Only now, and 2 months into this fiasco, did they come to the conclusion that it needed a new engine.
 

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I’m just regurgitating what the service advisor told me, which doesn’t mean much, since he seems to stutter when I ask specific questions.
To reiterate, your presentation was a straightforward, almost certain to be a mechanical problem. The code combination pointed at timing. The symptoms suggested to me, timing skipped and possibly valves were bent. All direct injected GM 3.6l motors have domed pistons, so you can be sure it is an interference engine.

My understanding of how the actuators work, having disassembled a few and data logged and graphed what happens at startup and idle, doesn't add up with oil starvation being the cause. If the oil pressure is not sufficient, the actuator can not be unlocked and will remain in the parked position. Given documented adequate oil pressure at idle being ~12 psi for the 3.6L and no indication that you had an oil pressure problem, I don't see an opening to connect the two, as an out of control, or synch camshaft can be easily identified by comparing its degree angle to that of the camshaft on the opposite bank, as well as what the computer commands, which their equipment can easily do.

I believe you either had the misfortune of an acute jump in timing, resulting in bent valves, or the technician jumped to conclusions on the fix, given the common occurrence of timing chain related problems, skipped diagnosing to confirm, replaced the chains, only to be greeted by the same problem and not realizing the valves were bent, assumed actuators were the cause twice, until someone else came along and pointed out the gap between the cam and valves, suggesting they were bent. The tech could also have made an error during install resulting in bent valves, especially if they were checked and found okay before chain install, which may have caused confusion when the problem persisted.

The tech could have ruled out the non locking actuator hypothesis by unplugging the solenoids. The actuators lock by default, with the solenoids disabled, the actuators will all remain uniformly parked. Don't be intimidated into accepting the outcome by the engineer title. Have the tech tell you what happened, the service advisor doesn't know.
 
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