Sticky lifter in 2001 STS

I have a 2001 STS with 50,000 km on it (bought used at 45,000 km). When the engine is cold, I hear the distinct sound of one or more sticking lifters.
I added top-end clearner to the oil and it certainly improved, but is still there. I've taken it to the dealer who de-carbonated the engine (no change).
What else can I do? What would be the impact of a sticking lifter longer term?
Thanks Mike
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"Mike" wrote

I'm unable to actually hear the noise in your vehicle, so it's possible you might have a sticky lifter, but I work on Cadillac motors and for the record....have never seen a sticky lifter or lifter noise from that year of vehicle. But, we do see plenty of the Northstars that make a noise that "sounds" like a lifter, but it is usually a noise caused by carbon on the pistons. Which is why your dealership performed the decarbonization procedure that is recommended by GM for this engine. Question is, which procedure did they use? There is one procedure that doesn't work that well, we always use the more aggressive procedure now. And, we have had some engines that require more then one application before the noise goes away.
Ian
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snipped-for-privacy@hotmail.com says...

I think too many people baby those northstars. They're a de-tuned race engine, get them up in the rpm range they start to breath in and they may not carbon up so bad. Same goes for the LS1.
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"Bonneville" wrote

Very true...that Northstar needs to be driven like you just stole the car. They will take whatever you can throw at them. I haven't seen one blow up yet that wasn't due to some sort of low oil condition, or lack of maintenance. And I've seen very few actually blown up.
Ian
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I all of a sudden have an urge to go take a STS for a drive.
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An old trick to loosen a sticky lifter is to put in a quart of transmission fluid. AT fluid has detergents that will loosen things up in a few hundred miles, then change the oil.
mike hunt
"Bonneville" wrote:

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I suppose I'll have to take it back to have it decarbonized again. What are the details of the more effective procedure (so I know what to ask for).
Strangely, the top-end cleaner had an effect...any idea why that would have quited the motor so much?
-Mike-

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