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Broke something...its not pretty...
- Thread starter boombots
- Start date
It looks like the 1987 Buick Riviera had the highest torque transverse mounted 90 degree V6 without balance shaft, Supercharged versions from the 90s and 00s have more torque and a balance shaft so they might be a good source.
Cadillac has a history of transverse mounted V8s so I will look there too.
Cadillac has a history of transverse mounted V8s so I will look there too.
After removing my broken mount and swapping it for a new one, I used some vise grips and a crescent wrench to remove what was left of the old bolt from the motor mount.
The bolt that fails is held in to the mount with some sort of thread locking compound, not impossible to remove by hand but it was a pain in the butt.
After the broken bolt was out, I looked and there is plenty of meat to drill out the mount and tap it with a larger thread, 9/16" fine thread is looking good.
The depth of the hole looked to be about 48mm including the aluminum bracket. There were several threads engaged in the hole, I think a 40mm bolt would be fine for people who want to replace the stock fastener. 50mm with a stack of washers might work too.
I didn't like what I had to do to remove the mount so what I might do is use a 9/16" stud with fine threads in the motor mount and coarse threads on top, then make a sleeve with a crush strength equivalent to a M12 10.9 bolt so that if I apply too much torque I'll crush the tube and make the mount loose and noisy rather than break outright. If there was enough force to break the stud, it would break at the coarse thread, hopefully leaving me enough stud to grab with vise grips and remove in the car for a quick fix without motor mount replacement.
Looking around, Dorman makes a 9/16" stud about the right size and costs about $22 for 10 of them in Grade 8 strength (it's a wheel stud I think).
I looked at proof loads and 9/16" coarse thread is about 73.4% greater than M12 10.9 so that's my upgrade path.
The bolt that fails is held in to the mount with some sort of thread locking compound, not impossible to remove by hand but it was a pain in the butt.
After the broken bolt was out, I looked and there is plenty of meat to drill out the mount and tap it with a larger thread, 9/16" fine thread is looking good.
The depth of the hole looked to be about 48mm including the aluminum bracket. There were several threads engaged in the hole, I think a 40mm bolt would be fine for people who want to replace the stock fastener. 50mm with a stack of washers might work too.
I didn't like what I had to do to remove the mount so what I might do is use a 9/16" stud with fine threads in the motor mount and coarse threads on top, then make a sleeve with a crush strength equivalent to a M12 10.9 bolt so that if I apply too much torque I'll crush the tube and make the mount loose and noisy rather than break outright. If there was enough force to break the stud, it would break at the coarse thread, hopefully leaving me enough stud to grab with vise grips and remove in the car for a quick fix without motor mount replacement.
Looking around, Dorman makes a 9/16" stud about the right size and costs about $22 for 10 of them in Grade 8 strength (it's a wheel stud I think).
I looked at proof loads and 9/16" coarse thread is about 73.4% greater than M12 10.9 so that's my upgrade path.
Ford sells the motor mount complete, the bolt is not available separately as far as I know.
You can try to find a bolt the right size but looking at the mount it seems like some special tooling is used to torque the bolt while aligning the bracket without putting undue torque on the rubber boots of the hydraulic bushing.
You can try to find a bolt the right size but looking at the mount it seems like some special tooling is used to torque the bolt while aligning the bracket without putting undue torque on the rubber boots of the hydraulic bushing.
Add me to the list of broken top motor mounts. I sheared the bolt and broke an axle in the process. I am currently fighting the dealer on this one. They said because of my mods they don't think they can cover it. I don't even have an aftermarket RMM. When I get it back I will replace the bolt with something of the stainless steel variety.
Stainless steel does not mean stronger.
There are some stainless allloys that make good fasteners but many of the best fasteners are not "stainless".
Stainless can have drawbacks like galling issues also. Their strength can be corrosion resistance or strength at high temperatures, you don't really need that in a motor mount bolt.
What you want to look for is ultimate tensile strength, yeild strength and elongation%.
High elongation% means the bolt is ductile and tough. High yield strength means that it can take a large load before it permanently deforms, high ultimate tensile strength means that it takes a large load before it will snap.
When you are looking, don't be tempted by a high UTS if the elongation is small, that means your bolt is brittle.
I want to go for a larger diameter fastener because that let's me use a much more normal fastener with good elongation and yeild strength for a large increase in strength.
The stock bolt is a metric 10.9 grade bolt which should be very strong already, there is only so much improvement that can be found with the alloy of a bolt and most ultra high strength bolts are brittle.
There are some stainless allloys that make good fasteners but many of the best fasteners are not "stainless".
Stainless can have drawbacks like galling issues also. Their strength can be corrosion resistance or strength at high temperatures, you don't really need that in a motor mount bolt.
What you want to look for is ultimate tensile strength, yeild strength and elongation%.
High elongation% means the bolt is ductile and tough. High yield strength means that it can take a large load before it permanently deforms, high ultimate tensile strength means that it takes a large load before it will snap.
When you are looking, don't be tempted by a high UTS if the elongation is small, that means your bolt is brittle.
I want to go for a larger diameter fastener because that let's me use a much more normal fastener with good elongation and yeild strength for a large increase in strength.
The stock bolt is a metric 10.9 grade bolt which should be very strong already, there is only so much improvement that can be found with the alloy of a bolt and most ultra high strength bolts are brittle.
I just came off of a short second gear WOT pull and and shift into 3rd to cruise at speed. I hadn't even given it has in 3rd when it broke. I only new something was very wrong when I heard a crunchy noise when I gave it a bit of gas.
[MENTION=4182]Wimp Lo[/MENTION]. I'm going to a bit of research on what I have here it my workplace. Being in industrial manufacturing I have isles of bolts most of which are stainless. I'll go through our fastenal catalogue and see exactly what we have in stock. You're given me enough info to get a good head start. Thank you.
[MENTION=4182]Wimp Lo[/MENTION]. I'm going to a bit of research on what I have here it my workplace. Being in industrial manufacturing I have isles of bolts most of which are stainless. I'll go through our fastenal catalogue and see exactly what we have in stock. You're given me enough info to get a good head start. Thank you.
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