Broken Motor Mounts

[Kenny D]

I went ahead and purchased the Anchor brand from Advanced. Lifetime replacement plus, I get a 20% cash back through my bank rewards. I know I paid 3 times what they were on RockAuto, but they are just down the street when I need another. By the way, I stored my receipt in a cool dry place for preservation. Now just to schedule a day to install it.

 

[iamdub]

You should scan and print your receipts because the print on the thermal paper will still degrade and fade.

 

[Da90]

So I replaced the mounts in my Denali when I first bought the truck. They lasted less than a year. I wasn’t going to replace them again until I found a fix.

I may have let my motor mounts go a little longer than I should have.

On to the carnage and solution.

Driver side

Passenger side

Solution. I first notched the heat shield. I then took two pieces of 1/8” x 1” strap steel and welded it to the bottom crossmember bracket and the bracket that bolts to the block. I sure hope this works cause the Suburban we bought a few months back also has broken motor mounts.

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[08grey]

Thats gonna feel like a solid mount. You need some play.

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[Meccanoble]

So where is the point of failure? I dont know enough about mounts but sounds like its not the rubber thats failing. I believe tougher mounts would lead to more vibration? What made you decide to go this route? The rubber is not failing but instead the mount is breaking at the metal? If so, why would reinforcing the break points not work? Isnt it the rubber that is doing the playing?

 

[Da90]

Thats gonna feel like a solid mount. You need some play.

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I was worried about that. No vibration whatsoever! Feels just like stock.


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[Da90]

So where is the point of failure? I dont know enough about mounts but sounds like its not the rubber thats failing. I believe tougher mounts would lead to more vibration? What made you decide to go this route? The rubber is not failing but instead the mount is breaking at the metal? If so, why would reinforcing the break points not work? Isnt it the rubber that is doing the playing?

The point of failure is the rubber. Too much flex. This is a picture of original mounts that I replaced first.

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[08grey]

The point of failure is the rubber. Too much flex. This is a picture of original mounts that I replaced first.

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Here is a solid mount a member on another forum made.

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[08grey]

I have a new mount on the shelve right now I need to Install. How much to send it to you to add the steel? I'd be down to give it a shot.

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[iamdub]

So where is the point of failure? I dont know enough about mounts but sounds like its not the rubber thats failing. I believe tougher mounts would lead to more vibration? What made you decide to go this route? The rubber is not failing but instead the mount is breaking at the metal? If so, why would reinforcing the break points not work? Isnt it the rubber that is doing the playing?

The mounts are hydraulic, so they're basically oil-filled balloons. This is great for damping the vibes when running in 4-cylinder mode, but insufficient for the engine's torque when moving such a heavy vehicle. Trucks that tow tend to break the mounts much sooner. Over time, the rubber hardens so it isn't as flexible/elastic and it cracks. The fluid leaks out so now there's just a small amount of dryrotted rubber acting as the cushion which is hugely insufficient. This rubber is easily and excessively stretched and squished constantly from the engine loading and unloading, so the hard parts inside the mount are able to wallow themselves out some wiggle room. Eventually, there becomes a void where it's just metal on metal and the halves of the mount are like two links in a chain hanging freely then being abruptly pulled taught every time the engine torques.

 

[iamdub]

I was worried about that. No vibration whatsoever! Feels just like stock.


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I don't know how you don't feel vibes. Maybe your engine just idles so smoothly? Does it have AFM?

 

[iamdub]

Here is a solid mount a member on another forum made.

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This is how I plan to fix mine except I'll use rubber mounts.

 

[2011SSVHOE]

I remember back in the sixties Chevy had a problem with the small block mounts, the recall put a small steel cable around the mount so that the engine wouldn't torque over.
So 45 - 50 years later they still don't know how to make a motor mount.

Back in the 80's Mercedes 190E had liquid filled motor mounts, Great idea, no vibration but a very high failure rate due to excessive heat from the exhaust. Recall solution Install a cooling vent duct from the front to the motor mount. Gotta love that German engineering.

 

[Da90]

I don't know how you don't feel vibes. Maybe your engine just idles so smoothly? Does it have AFM?

I have the AFM turned off with a custom computer tune. I was really expecting vibration and was ok with that as long as I didn’t have to replace them anytime soon. I was honestly shocked/excited when I first drove it that there was no solid mount vibration. I went back and forth on how I wanted to do this. I let the mounts sit on my work bench for months brainstorming. I got sick of trying to over engineer this and went for it. My truck doesn’t run all that smooth compared to my 06 Tahoe and 09 Suburban. That being said... I’m about to do the exact same thing to my Suburban. When it’s complete on that truck I will be able to really tell if there is a vibration.


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[Da90]

I have a new mount on the shelve right now I need to Install. How much to send it to you to add the steel? I'd be down to give it a shot.

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I would do it for $50 and you pay shipping.


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[Meccanoble]

Glad to hear there is no vibration. But according to other member, the failure is due to too much rubber or something not associated with how its held? How does strengthening the frame prevent the rubber from getting damaged?

 

[iamdub]

Glad to hear there is no vibration. But according to other member, the failure is due to too much rubber or something not associated with how its held? How does strengthening the frame prevent the rubber from getting damaged?

The flat bar that he welded in solidly connects the two halves which makes it rigid mount. The rubber between the two halves isn't doing any cushioning, it's just "there".

 

[iamdub]

I have the AFM turned off with a custom computer tune. I was really expecting vibration and was ok with that as long as I didn’t have to replace them anytime soon. I was honestly shocked/excited when I first drove it that there was no solid mount vibration. I went back and forth on how I wanted to do this. I let the mounts sit on my work bench for months brainstorming. I got sick of trying to over engineer this and went for it. My truck doesn’t run all that smooth compared to my 06 Tahoe and 09 Suburban. That being said... I’m about to do the exact same thing to my Suburban. When it’s complete on that truck I will be able to really tell if there is a vibration.


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No AFM explains it. V8s generally run smoother than 6- and especially 4-cylinder engines and the LS engine is pretty smooth. Just some (most?) have random shakes and/or vibes at idle, and that's when you're gonna feel them, if any. I had poly mounts on my S10 (V6) and it buzzed everything at idle but instantly smoothed out as soon as it was revved any amount above idle. Like you, I was ok with it cuz I was content in knowing the motor wasn't going anywhere.

Looking forward to your updates on this.

 

[iamdub]

...Recall solution Install a cooling vent duct from the front to the motor mount. Gotta love that German engineering.

"Yo, I'm diggin' those high-performance brake cooling ducts!"

"Those are actually to cool my motor mounts..."

 

[swathdiver]

Some engines must use rubber mounts as they are part of balancing the engine. A solid mount would soon tear the engine apart. I thought that I read somewhere these LS engines were that way too. Such was the case with the old Buick V6s.