Sounds scary but your 2 trucks and 2 new ones on the lot do it too? Must be normal.

 

Yea. I mean, I don't remember my 2015 v6 colorado making this noise but I cringe every damn time I start this truck now. I have a hard time believing this is a normal operation. Maybe the cam chain is slapping or lack of oil pressure or rather the new cartridge filter is lacking a bypass. I have no idea.... I figured maybe some other 2017 owners would have the same issues but I guess not TOO many people have 17's yet.

 

Ok, So, I've got some audio just now. Tell me what you think. RIGHT AT 9 to 10 second transition you can hear it. It is only there for maybe a second cause the truck has only been sitting for 4 hours. It's worse after all night or a few days without driving it. Thanks.

Vocaroo | Voice message

 

I'm stumped, sounds too fast for an internal engine problem that I've ever heard. I guess it could be something to do with variable valve timing or the cyl cut out stuff? It does sound like something loose until the oil pressure comes up but wow, don't know. But either way if 4 new trucks do it I would think its normal. Although its not like a normal sound a vehicle should make too right? Weird....Hopefully some other 17 owners will chime in.

 

I would not over think this.

Today's cars make some crazy noises at start up.

My other car makes a loud roaring sound as when cold a door is open on the intake and you hear the air more for about 30 seconds.

Then there is another item when you shut it off that sounds like a ball bearing rolling and then a door shuts. Both are normal and due to cold start emissions.

Today's cars while similar are vastly different than even a couple years ago.

You can have a dealer check it but I wager they all do it and it is normal. The truck have two low of miles to have a piston slap or any rare fatal ness about them.

Like stated it could be something on the AFM.

 

Hey forum peeps,

So my 2017 Colorado, as well as my 2017 Canyon, both with the 3.6L v6 and both with 800-900 miles on them, makes a very strange noise on a cold start up. I tried searching but only came up with 1st gen stuff.

Thanks!

That short rattle is likely one of the hydraulic chain tensioners. The previous LFX 3.6L and even my 2010 3.7L I5 Atllas engine did that short "rattle" sound upon a cold start if you really listened for it. The newer LGX and LGZ 3.6L engines use similar timing chain design elements. And. . I would be willing to say your previous Twin did it as well with the LFX 3.6L, but maybe not as pronounced. My 2017 also has that and sometimes more noticeable than others. Not a concern. It could also be the hydraulic valve lifters pumping up upon a cold start. Oil drains back over some hours of sitting.

It takes a second or so for the hydraulic timing chain tensioner to tighten up by means of engine oil pressure on it. The tensioners work on one or more of the chain guides on the slack side of the timing chain. Some tensioners may only have a spring behind them to do the job. There may also be a balance shaft chain in these engines with a tensioner.

The timing chain has a series of chain guides with one or more also operated by an oil pressure tensioner. Below is a picture of a typical V6 Overhead Cam V6 engine (the GM 3.6L LFX I believe). The red arrows point to three tensioners and the blue arrows are other timing chain guides.

 

Normal 3.6L LGZ Cold Start Rattle.

I believe owners are reporting 2 or possibly three concerns here.
1. Initial oil pressure actuated Timing Chain Tensioner slack on cold engine starts. Normal operation - - no worries/no repair needed.

2. Possible Valve Lifter drain down or leakage. Repair required.

3. The occasional Cam Shaft Actuator malfunction. Repair may be required.

Both the older 3.6L LFX and newer LGX/LGZ V6 engines have Timing Chain tensioners that will drain back the oil required to pump them up when not running for several hours or over night. This is the predominate sound most would hear for a few seconds upon a cold start or after several hours of the engine not running and restarted.


See below:

That short rattle is likely one of the hydraulic chain tensioners. There are both spring operated and oil pressure actuated tensioners. The previous LFX 3.6L and even my 2010 3.7L I5 Atllas engine did that short "rattle" sound upon a cold start if you really listened for it. The newer LGX and LGZ 3.6L engines use similar timing chain design elements. And. . I would be willing to say your previous Twin did it as well with the LFX 3.6L, but maybe not as pronounced. My 2017 also has that and sometimes more noticeable than others. Not a concern. It could also be the hydraulic valve lifters pumping up upon a cold start. Oil drains back over some hours of sitting.

It takes a second or so for the hydraulic timing chain tensioner to tighten up by means of engine oil pressure on it. The tensioners work on one or more of the chain guides on the slack side of the timing chain. Some tensioners may only have a spring behind them to do the job. There may also be a balance shaft chain in these engines with a tensioner.

The timing chain has a series of chain guides with one or more also operated by an oil pressure tensioner. Below is a picture of a typical V6 Overhead Cam V6 engine (the GM 3.6L LFX I believe). The red arrows point to three tensioners and the blue arrows are other timing chain guides.

I was hoping this 'New' design would solve the oil drain issue, but possibly not.

 

Sounds like the lifters going nuts on the start up. Which might make sense because the V6 are Variable Valve Timing(VVT) right? So maybe thats just the start up sequence to help fight the cold start emissions? I dont know, just throwing out some bs.

 

my 17 canyon does this intermittently. im not worried about it.

 

OK, I started both this morning to investigate this, and they do it too. I concur that it is parts of what everybody's listed being employed.

 

Well what ever it is making the noise it's got 5yr/60k miles to PROVE if it is normal or not. >

 

Mine does the same thing, was a bit concerning when I first heard it, but it's :gmc 's problem until 50k miles.
My crany pulley looks to wobble slightly too, this was a known issues on the LS1's and I've had it replaced, oh well, maybe it will grenade at 40k miles or so and I'll get a new engine, compliments of the general. >

 

Mine Too!

Mine does this exact noise as well. Not every time, but about 5 times now. I think it's the AC clutch, but not sure. Looks like were all in the same boat. Let's all of us work together to see what this is. :serious:

 

The "rattle" is likely the hydraulic timing chain tensioner as I mentioned earlier.

This is a well known quirk on many brands of newer overhead cam engines with the long timing chain paths that they must circumnavigate.
This is not to be confused with a chronic stretched timing chain or timing chain guides which was another problem on earlier engines. The noise from that issue was constant and you would hear it all the time.
As long as it last only for a few seconds upon a cold start it is not a problem. Worry when your hear rattles, knocks, or other nasty sounds ALL the time.

 

huh? what is it rattling against? The chain itself? Don't the tensioners have a healthy spring behind them too just for this reason? Could be the noise but I don't buy it.......just my guess

 

Okie Dokie then...

 

Hey, you axed:grin2:

 

Poll?

Anyone else? I guess we could start a poll. I talked with a lady who bought a truck the same day I did, and hers does it too. :frown2:

 

I am going to have to go with a chain tensioner.

It is not a lifter as they do not sound like that. Piston slap does not go away that fast.

I would take it to a dealer and either get them to find it. If they say it is normal then get them to show another new trick do the same.

Chains will make a diesel like sound and a tensioner will make it go away this fast with pressure. So I think he is right on this.

 

to tinny

I think it sounds like an exhaust shield like maybe on the exhaust manifold or cat converter. That don't sound like it's inside engine. It seemed to do it as it started while the engine shakes for a second or two. it's to tinny to be in side.
Just my comment. anyway hope that's it. I have heard that sound on my brothers vette.

off road bob

 

I think it sounds like an exhaust shield like maybe on the exhaust manifold
off road bob

We don't have exhaust manifolds. They are molded/built into the heads, so that it is only a single exhaust collector exit. The design was made so that a turbo could be bolted directly to the head, and cut down on all the extra plumbing and bracketry.

 

I haven't heard anything out of the ordinary on my 2017 upon startup...i just sounds like a GM engine starting up.

 

Well no kidding! lol


No noise like that on yours?

 

I still think it could be the AC clutch, but what do I know.

 

The noise lasts so briefly - clearly either the lifters or tensioner momentarily being slack before oil pressure comes online. It is such a rapid and short lived noise, I am going with the lifters.

 

Not lifters. You will not bleed down that many lifters to make that much noise on start up. Now that kind of noise comes when the pump fails after it is running.

Tensioner is the most likely issue.

Tried my remote and no noise.

Note I have heard similar on the Ecotech 4 cylinders and it was the tensioner.

 

I didn't hear anything like what OP posted when I started my vehicle up yesterday.

 

Like I said, It comes and goes. Most often, it is there on COLD starts. But, since I posted this thread and I started the truck 5 times, I have not heard it back yet. Very strange...

 

Hey, it fixed itself, cool!

 

Could even be the starter drive is intermittent issues.

 

Another data point. My '17 Canyon makes that sound for about that length of time in the sound clip. 5ish times in about 30ish startups since I purchased. I have a little under 500 miles on odometer.

 

Yup! That's about the frequency of mine, too!

So....so strange.....

 

Mine did it once over the weekend. Thus far this engine is the nosiest on start up of any I've had, not counting this particular noise. I'm glad I have a lifetime powertrain warranty. :serious:

 

Mine has been doing it occasionally too. I'm at 450 miles.

 

Bump