07 Sierra Denali Has Cold Start Knock

[Black02Silverado]

A friend of mine just purchase an 07 Sierra Denali back in June and has 6800 miles on it now and just now started noticing the cold start knock. From what he has described it to me that is what it sounds like. Is anyone else having the same thing happen with their 07 Denali?

 

I thought GM took care of that issue.

[99silverado1500]

I thought so to, but I was at the dealer looking at new trucks, and a brand new suburban that was sold that day, had a cold start knock and a nasty valve tap when the new owner took off. Its because of sloppy fit and the short skirt pistons. Its a GM thing, as my neighbors buick suv, whatever the model is, has a cold start knock on their V6.

[bryanhunt]

Until the trucks come from the factory with synthetic and GM tells you to change the oil with synthetic it sounds like you'll always have some engines with cold start knock. People that switched to it right out the gate seem mostly fine, those with little wear synthetic seems to reduce the severity of the knock as well.

[ChrisNJ]

I have an 07 Seirra Denali. I also had an 02-6.0 with piston knock and know exactly what it sounds like. GM gave me a 100K warranty on that 02, and it went 80K trouble free, never burning oil, etc.., worked it very hard towing big. It only knocked in the colder winter months at startup for about 15-20 seconds, but was very apparent.

Now this 6.2 does have a noise at start-up, but it is not a piston to my best estimation. It is a lifter noise, very slight, but it is there untill warmed up completely. It does not happen at idle, you have to give it some gas under slight load. A piston moves twice vs a lifters once, per cycle. The truck was in for it's fist oil change and I asked the dealer to investigate, telling them 'it's up to you, it has 100K warranty, and i'd rather not deal with it, your call' They said normal. I have 6K on it.

My wifes new 6.2 has not made this noise, although at around 800 mi. it's just starting very slight same noise. and i mean very very slight.

keep in mind i am an anal mech engineer, that raced engines under my legs at 13Krpm, that if they had trouble i could easily die. my ears are tuned for this stuff. my guess is a very high percentage of owners wil not hear it at all.

and with 100K warranty, i really don't care, i never keep them past 75-80K.

and i never use synthic oil, had an engine blow up with the early 90's synthetics, and it scarred me. no offense to synthetic users but for me it's not required if i get a new engine every 3-4yrs or 80K.

[cc1999]

So far so good with the new Suburban 5.3, but my last GMC pickup with the 5.3L started the vortech knock (as the dealer called it) @ about 60K. I had that GMC in the shop 4 times and spent about 400.00 and it still knocked every morrning on the way to work, for about 2-3 blocks and again when I would leave work in the evenings for 2-3 blocks, just untill it would get warmed up. I could not stand it. The Dealer did give me a GM bulliton that stated that it was normal, I just thought that it was not normal for the first 60,000 miles, when it never knocked, why is normal now? I sold that truck and bought a Dodge with a Hemi. I swore I would never have another 5.3L, but they convinced me that problem had been resolved when I bouhgt my 07' Suburban . I guess not. I also thought it was just the 5.3L and 4.8L, I guess not on that one as well.

[croos]

No problems with mine @ 3K. Will be going with full syn (Mobil 1) very shortly.

[bryanhunt]

and i never use synthic oil, had an engine blow up with the early 90's synthetics, and it scarred me

 

It was probably a 90s sludge-matic and not the synthetic... (synthetics were already 20 years old by that point anyway)

[mljenkins]

I noticed this morning (~50 F outside) as I started the truck (06 Silverado w/ 5.3) and walked around to wipe the dew off my mirrors that it had a slight knock for about the first 30 seconds of run time. I've never heard it before. It's due for an oil change and I will have them do the BG service again to clean things out. I'll have to remember to post a follow up. A lot of folks on the net swear by some of the BG products to eliminate that from happening.

 

It seems the piston slap is more common on a lot of newer cars. My brother's mustang (I think an '05) has a nasty slap noise for the first couple minutes it is started. I've heard a lot of other complaints from people that drive other newer vehicles.

[gmblack3]

Nothing so far at 650 miles on my 6.2. I plan on going to M1 oil and filter at my first oil change. Somewhere from 1500-2k miles. Is there less of a chance of getting noise if you change to synthetic sooner?

[hoot29576]

the 6.2 comes with synthetic from the factory.

[topdj]

Well he can trade me my truck has no knock LOL

[Bostonsfavson]

the 6.2 comes with synthetic from the factory.

 

Mine didn't.

[Fyrcaptain]

the 6.2 comes with synthetic from the factory.

 

 

I thought only the Corvette had a synthetic factory fill and the oil fill cap with M1 synthetic logo on it?

[hoot29576]

I had my oil changed last week in my sierra denali and was told that it had synthetic oil in it. I put mobil 1 synthetic in it at the change.

[Black02Silverado]

Update on my friends Sierra Denali engine knock. He took it to the dealer not to long ago for the start up knock and they told him it was normal not to worry and that he had a 100k warranty. Then he calls me today to tell me that the dealer called him and wants the truck in there now and they are going to pull his entire engine fully dressed and install a brand new fully dressed engine and that they have to ship his engine off to GM within 48hrs of when it was pulled out of his truck.

 

Anyone feel something isn't quite right with this. To first get the usual nothing is wrong to getting a call out of the blue stating that they want your engine now and it will be replaced with a completely new dressed engine?

 

Hmmmmmm.

 

To me that is great, to get a brand new completely new engine and done in a speedy manner. I would assume the warranty would start from zero on the engine?