NEED HELP Vibration

Hearnrobert2828

Original poster
Member
Dec 8, 2019
8
Knoxville
Hello. So I just bought a 2007 trailblazer LS. I replaced the control arm on driver side. I have a vibration I cannot seem to get rid of. I don't know how to decide if it's a motor mount or something else entirely. I was putting it in neutral at lights and that would cause it to stop until I put it in drive again. But it doesn't happen constantly. If it is a mount wouldn't it do it every time driven? Any help would be greatly appreciated. Thanks!
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Thread title changed.

When do you feel this vibration? Moving? Not moving? Idle? Park/neutral?
 
I had a vibration that I couldn't figure out for the longest time, eventually I had my wife rev it a bit while I was checking around, turned out to be the thermal plating above the exhaust had rotted and was bouncing around. specifically it was right above the CAT.

point is, does it only make the noise while driving or can you get it to do it in park
 

Hearnrobert2828

Original poster
Member
Dec 8, 2019
8
Knoxville
Thread title changed.

When do you feel this vibration? Moving? Not moving? Idle? Park/neutral?
Mostly only when u come to a stop at a light and the engine is at idle. A few days ago I could put it in neutral and it would subside but now (when it happens) regardless of what gear it's in it vibrates.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Does it go away once you get moving again?
 

Hearnrobert2828

Original poster
Member
Dec 8, 2019
8
Knoxville
Hello. So I just bought a 2007 trailblazer LS. I replaced the control arm on driver side. I have a vibration I cannot seem to get rid of. I don't know how to decide if it's a motor mount or something else entirely. I was putting it in neutral at lights and that would cause it to stop until I put it in drive again. But it doesn't happen constantly. If it is a mount wouldn't it do it every time driven? Any help would be greatly appreciated. Thanks!
It mainly comes from the engine bay.
 
Have you checked on your heat shielding? without knowing how bad the vibration is, we can only guess. I would check on it as well, ive seen a lot of 360s come in expecting huge repairs and it ends up being something small like a heat shield. Usually the one right above the CAT which is basically in the engine bay,

Have you popped the hood and tried to identify where its coming from? or have you only experienced the vibrations from the drivers seat?
 
If your facing the engine, on the left where the exhaust manifold is, if you look down you can see the CAT sitting right at the end of the manifold, the heat shielding is above it on the body of the vehicle. its held in with some small bolts, but they like to rot in that area and when they rest on the exhaust they will vibrate and they tend to stop when you give it some gas,

That may not be the issue because I'm not there to experience how strong the vibrations are, but its something small to check in a few seconds anyway, but I would definitely pop the hood with the engine running and see if you can narrow down the vibration to a specific area
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
How much mileage? If it's a 10Hz vibration that goes away when off-idle, it's likely the engine mounts. Do however check for any exhaust related components rubbing or hitting the body or frame.
 

Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
I would try to inspect the motor mounts. See if you can see any goo seeping out from the top of the rubber mount or if they look warped/off balance. If you can take a picture of them and let us see them as well that would be helpful. Is your CEL on? A vacuum leak could be a cause of a slight vibration.

There is also a little heat shield on the passenger's side motor mount. I would inspect that as well to see if it has come loose or corroded. I you decide to gamble on replacing mounts, I would start with the passenger's side mount. Since it is near the heat of the exhaust manifold, it is more likely to give up the ghost first.

I would do the 10hz vibration test first as @Mooseman suggested. That's usually a dead giveaway that the mounts are bad.

I found this picture of a mount that is leaking.
1576155540337.png

Here's a good video showing what kind of vibration you could see with bad mounts. When mine went bad it only vibrated at idle and (I think) 1500 or 2000 RPM's.

 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
And if it is the mounts, get only ACDelco. Others don't dampen the vibrations properly.
 
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Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
That'll do it! I would spray those bolts with your preferred lubricant, heat the engine up, then use a torch to heat the bolts, then tighten them down. They are likely to brake otherwise and still might brake even with those steps.

You could also just keep lubing them up a few times a day for about 3 days and that might allow them to be tightened. Not sure of the rust that you may have considering you live in TN. If they don't look very rusted then you might be able to tighten them as is.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
If you are in "The Rust Belt"... it can be caused by a "Skin and Bones" Vibration Problem:

Skin (If some of the Small Studs-Fasteners have Rusted away):

EXHAUSTMANIFOLDSHIELD.jpg

Skin and Bones (...and then Rattle like Hell in between like an Echo Chamber at certain RPM):

EXHAUSTMANIFOLDSHIELD2.jpg
 

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