Want to buy 06 Envoy XL Denali but tapping ..

BurnKero

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Hey guys,

I have my eye on an 06 XL Denali, Very nice vehicle. It has 75k on the clock. Its condition in and out is spectacular. The dealer has said they can produce maintenance records for me as well, Ill find that out tomorrow.

They are asking 17,900. Which I feel is a bit much, I feel if they knocked it down 1k, it would be more comparable to other Denali's Ive seen.

I absolutely love the truck, Perfect for my application. One big concern I have though. I noticed that there is a fairly pronounced tap/knocking sound that starts around 1.5k and fades away through 3.5/4k. It is present driving and parked in neutral. I first heard it under heavy acceleration during the test drive tonight, the engine was at operating temp. The vehicle seemed to have a harsh shift out of first while under heavy acceleration. Normal acceleration produced smooth shifts.

After we returned to the dealer, I popped the hood and rolled the engine through that particular range to confirm what I thought I had heard. It was indeed a good tapping sound that remained present the whole time I held the engine at 2k.

I would say something in the valvetrain? Is the vortec valvetrain know for this?

I would appreciate some input before tomorrow afternoon where I will be returning to the dealer with my mechanic. Thanks in advance!

Pete
 
It sounds like a bad lifter and needs to be replaced, at best it could be dirty and running Marvel Mystery Oil with the engine oil could clean up the oil journals and free up the lifters. Common cause of lifter failure is carbon build up due to lack of oil change or running the engine low on oil. Inspect the PVC valve and the inside of the oil cap for signs of excessive carbon build in the engine and also look down the throttle body by opening the throttle blade wide open and look to see how much carbon build up is on the back side of the throttle blade which would indicate what life the engine had by the previous owner. Good luck and enjoy your new toy.
 


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