1st Mechanical Issue
 

Hi folks,

So I'm going to take the truck by the dealer later but I thought I would ask you guys in case you've encountered this issue before.

Everything works fine but when the engine goes from gas to electric I hear a slight grinding noise coming from the engine bay. It happens every time the gas engine shuts down, whether it switches to electric mode or when I turn off the truck.

Anyone experience this?
And if so, what is it?

Thanks.

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Edit to add: This noise is more noticeable when the engine is cold. For example it is more pronounced when the engine shuts down after the first remote start in the morning.

Re: 1st Mechanical Issue
 

Okay so I tried all afternoon to replicate the noise and could not.

Finally this evening I got it on audio/video.

You can hear it at the end of the video, right after I turn off the engine at the same time as the little engine off beep sounds.

http://www.youtube.com/watch?v=1SxASlAAjQc

Any thoughts?

Re: 1st Mechanical Issue
 

that doesn't like anything I have ever heard....how many miles do you have and does it only happen on a warm engine.....is the AC on.....could it be a fault in the ac or power steering pump as they are electrically driven?

Re: 1st Mechanical Issue
 

Hi jet1,

It's interesting, it only used to happen on a cold engine. I heard it a couple of times after the remote start cycle ended but didn't think anything of it. Then today for the first time whilst driving, it started doing it very faintly when the truck switched from electric to gas and when I was running at normal operating temperature.

It's the remote start element that has me thinking it isn't related to anything hybrid, as nothing of the 2-Mode is engaged during remote start warmup and then the engine just turns off.

Ugh! :(

Re: 1st Mechanical Issue
 

Okay ... I got a better recording of it with the hood up:

http://www.youtube.com/watch?v=o1TxqaHPEdE

sigh

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ETA: This is with a cold engine shutdown ... it gets a lot less pronounced when the engine is at running temp.

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Oh and jet, she has 25xxx miles on her.

Re: 1st Mechanical Issue
 

Serge,
I can't really hear the sound it loud enough from your video, but if it is a wining noise coming out from behind the front drivers side wheel, it would be the same as the sound I get on my 2010 Tahoe when it goes into Autostop as well.
It happens to me many times specially after a 15-20 mins drives or longer.
after askign the experts on this forum, I was told it is the Auxiliary pump that makes that sound, it does no harm, and GM are aware of it.
You can check at the dealer to see if they have a software update for that issue in your next visit.
I am waiting for my next oil change to take it to the dealer and have them look at it for a second time.
First time I showed them the video, they wanted me to leave the car, but I was in a hurry. Mine is still under warrenty though.

here is a video with the sound when it goes to autostop.

http://youtu.be/Bkz24zsseWc

hope this helps

Guss

Re: 1st Mechanical Issue
 

Serge: thanks for the second video. Have the dealer look at the throttle body for any build ups. 25k is real soon for this. I have seen it at 150k plus.

Re: 1st Mechanical Issue
 

Thanks HillBilly :)
So I guess it is a different issue than the one I mention in my previous post.
Thanks again

Re: 1st Mechanical Issue
 

those sounds seem all normal to me. no drivability issues.

Re: 1st Mechanical Issue
 

Thanks everyone ...

I'm at the dealership and they have the truck to try and diagnose the issue.

This is actually the second dealership I'm visiting cause the first didn't have time to deal with it. It is definitely not a 'normal' sound and neither service manager has ever heard it before.

So now I wait ...

Thanks again.