Broken Motor Mounts

[Rocket Man]

With how much I WOT mine, I'm still surprised you broke an ACDelco H3 mount so soon. Granted, I don't do many WOTs from a dig (no reason to), but still.

I also don't see how poly mounts wouldn't appeal to you guys' wives. I thought they liked that sort of thing. I guess an "O face" while being stuck in traffic could be a distraction for them, though.

They need more like a Harley vibration, solid mounts in a Tahoe would just be just a tease.

 

[Meccanoble]

They need more like a Harley vibration, solid mounts in a Tahoe would just be just a tease.

UPDATE!!! The H3 is NOT broken. The 4 bolts that connect mount to the engine are all gone!! Heading to Home Depot to find similar bolts. Any specific torque for these bolts? I'm sure I tightened them right before but I know I had trouble fitting in. I think I will keep the H3's in and return the solids if possible.

 

[Meccanoble]

Can anyone confirm the size bolt? I think all 7 are the same but would like to be as much prepared as possible.

 

[Foggy]

Metric for sure.. I'm thinking M12 thread. But not sure. Make sure you get
Grade 8 or better.. Gm uses the grade of 10.9, 12.9 kinda stuff.. I know it's
the Good Stuff, so only go with the high grade strength. I would use something
on the threads that go into the block- maybe a teflon paste to keep them from galling
and seizing into the block

 

[Meccanoble]

Metric for sure.. I'm thinking M12 thread. But not sure. Make sure you get
Grade 8 or better.. Gm uses the grade of 10.9, 12.9 kinda stuff.. I know it's
the Good Stuff, so only go with the high grade strength. I would use something
on the threads that go into the block- maybe a teflon paste to keep them from galling
and seizing into the block

Teflon paste? Is this similar to the stuff like red or blue that keeps the bolt sealed?

 

[Rocket Man]

UPDATE!!! The H3 is NOT broken. The 4 bolts that connect mount to the engine are all gone!! Heading to Home Depot to find similar bolts. Any specific torque for these bolts? I'm sure I tightened them right before but I know I had trouble fitting in. I think I will keep the H3's in and return the solids if possible.

Metric for sure.. I'm thinking M12 thread. But not sure. Make sure you get
Grade 8 or better.. Gm uses the grade of 10.9, 12.9 kinda stuff.. I know it's
the Good Stuff, so only go with the high grade strength. I would use something
on the threads that go into the block- maybe a teflon paste to keep them from galling
and seizing into the block

Teflon paste? Is this similar to the stuff like red or blue that keeps the bolt sealed?

Not sure on the bolt size or thread pitch. Service manual states mount-to-engine bolt torque is 37 ft-lbs and they don’t specify use of thread lock but I wouldn’t use anti-seize or “Teflon paste” because that might help them to vibrate loose. If you are worried about electrolysis or having the bolts seize in place I would use blue Loctite. It accomplishes the same thing along with being a medium strength thread locker which will help them hold.

 

[Meccanoble]

Not sure on the bolt size or thread pitch. Service manual states mount-to-engine bolt torque is 37 ft-lbs and they don’t specify use of thread lock but I wouldn’t use anti-seize or “Teflon paste” because that might help them to vibrate loose. If you are worried about electrolysis or having the bolts seize in place I would use blue Loctite. It accomplishes the same thing along with being a medium strength thread locker which will help them hold.

I'll probably just do without any. I have red but i think you recommended blue for a reason. I see grade 8.8 in the stores based off websites. I hope thats good enough.

Might be best to use the ones i currently have on the engine and the new ones on the body....?

 

[iamdub]

Can anyone confirm the size bolt? I think all 7 are the same but would like to be as much prepared as possible.

M10x1.50x20mm long

Use blue thread locker (Loctite, etc.) if you want. It's not a convenient place to fit a torque wrench but I've always torqued 'em down by hand as tight as I could get 'em in that area- about 2.75-3 solid grunt's worth of torque. Never used thread locker and never had any come loose.

20mm length isn't so common and you're likely to find 25mm or 30mm. Thread one in by hand and if it bottoms out, take it out and grind a few millimeters off the tip. You may wanna pick up an M10x1.50 nut to have on hand in case you need to grind the bolt down. Thread the nut all the way down on the bolt before you grind it. I recommend you use a flap disc and grind a slight taper into the edge of the tip. I just put a slight 45° on that edge and it's fine. No need to round it over or sharpen it to a point. When you're done grinding, removing the nut will act as a tap to fix and clean up the threads. You could always pull one outta the other side and take that with you to the hardware store for reference.

Aim for grade 10.9, but 8.8 will be fine.

Glad to know the H3 mounts are still good to go!

 

[Meccanoble]

M10x1.50x20mm long

Use blue thread locker (Loctite, etc.) if you want. It's not a convenient place to fit a torque wrench but I've always torqued 'em down by hand as tight as I could get 'em in that area- about 2.75-3 solid grunt's worth of torque. Never used thread locker and never had any come loose.

20mm length isn't so common and you're likely to find 25mm or 30mm. Thread one in by hand and if it bottoms out, take it out and grind a few millimeters off the tip. You may wanna pick up an M10x1.50 nut to have on hand in case you need to grind the bolt down. Thread the nut all the way down on the bolt before you grind it. I recommend you use a flap disc and grind a taper into the tip. When you're done grinding, removing the nut will act as a tap to fix and clean up the threads. You could always pull one outta the other side and take that with you to the hardware store for reference.

Aim for grade 10.9, but 8.8 will be fine.

Glad to know the H3 mounts are still good to go!

I am not familiar with grinding or any custom work involving bolts . I dont even have a grinder. If I cant find locally, i'll have to go to dealer on Monday. Looking for a link to send. I see zinc bolts. If I spray them with paint built for high heat, will that help in any way?

 

[iamdub]

I am not familiar with grinding or any custom work involving bolts . I dont even have a grinder. If I cant find locally, i'll have to go to dealer on Monday. Looking for a link to send. I see zinc bolts. If I spray them with paint built for high heat, will that help in any way?

No painting of any kind is necessary.

Here's some at Home Depot: https://www.homedepot.com/p/Prime-L...Hex-Head-Cap-Screws-10-Pack-9114719/310516216

Apparently, 20mm is actually a standard/common length. Maybe they're just always out of stock when I shop for them. They're out of stock at my local Home Depot. Get 20mm and you won't have to grind anything, just screw 'em right in, with or without a little thread locker if you want. You could stick something in one of the holes, and hold your fingernail on it to mark the depth so you'd know if a 25mm bolt would work in case the 20mm isn't available. Don't have a metric ruler? Just know that one inch is 25.4mm. So, if you have right at an inch of depth or a little more, then you can use a 25mm bolt. You could always use a thick washer to space it out if it comes to that. I'd get washers anyway. It's just four bolts in four holes- nothing complicated.

I'm sure any decent local hardware store (Ace, True Value, whatever mom-and-pop store is close to you, etc.) would have what you need as well. No need for dealership visit or cost, if they even have them in stock.

 

[Luie]

I had to replace my engine mounts a few years ago and for the life of me cant remember where or what brand they are. Im guessing off Amazon...

 

[Meccanoble]

No painting of any kind is necessary.

Here's some at Home Depot: https://www.homedepot.com/p/Prime-L...Hex-Head-Cap-Screws-10-Pack-9114719/310516216

Apparently, 20mm is actually a standard/common length. Maybe they're just always out of stock when I shop for them. They're out of stock at my local Home Depot. Get 20mm and you won't have to grind anything, just screw 'em right in, with or without a little thread locker if you want. You could stick something in one of the holes, and hold your fingernail on it to mark the depth so you'd know if a 25mm bolt would work in case the 20mm isn't available. Don't have a metric ruler? Just know that one inch is 25.4mm. So, if you have right at an inch of depth or a little more, then you can use a 25mm bolt. You could always use a thick washer to space it out if it comes to that. I'd get washers anyway. It's just four bolts in four holes- nothing complicated.

I'm sure any decent local hardware store (Ace, True Value, whatever mom-and-pop store is close to you, etc.) would have what you need as well. No need for dealership visit or cost, if they even have them in stock.

My goodness I feel blessed. Few things!

First, I thought the 4 bolts that go into engine were same as the one that goes into frame. The engine side is a LOT shorter than the side that goes into frame. If I ran to this trying to fix on my own, I would have been stressed exponentially!!!

Secondly, I went to Home Depot looking for a similar bolt but wanted the hex flange. Not sure if it matters. I found some but they were silver like these and the guy that worked there told me they were not rated Grade 8. The ones I wanted take a week to come in. I didnt look at the non flange type like what you sent.

I DESPERATELY ran to Napa with failure but O'Reilly's had a Dorman set that were rated Grade 10.9 and GOLD like the Home Depot guy recommended. I also got blue loctite to use just to play it safe as my torque ability in a tight spot is now questionable.

I am so grateful for all the resources I encountered today. I first looked at that mount and thought the bolts snapped in the engine (cried inside) to now being able to possibly get this installed today! I'll keep you all posted.

 

[gooffeyguy]

Just curious, because I'm not familiar with GM mounts, but how many bolts does one take for each side?

Sent from my SM-G930V using Tapatalk

 

[iamdub]

Just curious, because I'm not familiar with GM mounts, but how many bolts does one take for each side?

Sent from my SM-G930V using Tapatalk

Four on the engine block side, three on the frame side.

 

[iamdub]

My goodness I feel blessed. Few things!

First, I thought the 4 bolts that go into engine were same as the one that goes into frame. The engine side is a LOT shorter than the side that goes into frame. If I ran to this trying to fix on my own, I would have been stressed exponentially!!!

Secondly, I went to Home Depot looking for a similar bolt but wanted the hex flange. Not sure if it matters. I found some but they were silver like these and the guy that worked there told me they were not rated Grade 8. The ones I wanted take a week to come in. I didnt look at the non flange type like what you sent.

I DESPERATELY ran to Napa with failure but O'Reilly's had a Dorman set that were rated Grade 10.9 and GOLD like the Home Depot guy recommended. I also got blue loctite to use just to play it safe as my torque ability in a tight spot is now questionable.

I am so grateful for all the resources I encountered today. I first looked at that mount and thought the bolts snapped in the engine (cried inside) to now being able to possibly get this installed today! I'll keep you all posted.

Yes, the gold is the zinc chromate, the anti-corrosion coating usually associated with the high-strength machine bolts. It's durable but not thick so it doesn't cause fitment problems. Plain zinc is the bright silver coating which is a little less durable, is cheaper, and is more common everywhere else. There's a whole lot of other factors in bolt material and coatings but you can Google that if you ever find yourself bored enough to geek out on it. Glad you're making progress!

 

[Meccanoble]

The 2 bolts closer to the front of the car were easy, I was able to torque. I torqued to 50 ft/lbs to play it safe. The 2 on the side closer to the inside of car were harder as I remembered from previous installs. I was able to hand tight the one closest to driver side but will need a smaller ratchet with angles to properly tighten the last one. Needed a quick break

 

[Rocket Man]

The 2 bolts closer to the front of the car were easy, I was able to torque. I torqued to 50 ft/lbs to play it safe. The 2 on the side closer to the inside of car were harder as I remembered from previous installs. I was able to hand tight the one closest to driver side but will need a smaller ratchet with angles to properly tighten the last one. Needed a quick break

Be careful if your block is aluminum that you don’t over torque them and strip or deform the threads. Torque specs are for a reason and you went more than 25% over spec.

 

[Meccanoble]

Pictures

 

[Meccanoble]

The jack lifting the engine up has 7" high of wood. The top 2 pieces are no more than 3" wide.

 

[Meccanoble]

Be careful if your block is aluminum that you don’t over torque them and strip or deform the threads. Torque specs are for a reason and you went more than 25% over spec.

Thanks for the advice. I seen 100 tq would be ok and thought 50 would be no biggie. I ended up using a wrench to get that last bolt as tight as I could. That front DIFF seems to limit so much access.

My test drive was successful. Noise is gone and that start up seems quick.