Broke something...its not pretty...

[Hijinx]

Checkout quirkparts.com for what you need. It looks like the passenger side is a stud and nut combination. Part nos on quirkparts.com.

http://www.quirkparts.com/auto-part...ine/engine-cat/engine-and-trans-mounting-scat

Ehh... Numbers 6 and 7?

 

[westcoaST]

Below the exploded parts graphic are the part numbers. Scroll down to see the part numbers.

 

[westcoaST]

6. Part #: -W708873-S437

7. Part #: -W520204-S442

 

[Wimp Lo]

I seem to have broken my motor mount, the head sheared off.

On the bolt head, it is marked 10.9 so I think it should have been a good bolt.

I broke it being stupid, with sticky tires and a 3,000 rpm clutch drop from a stop.

Looking at the mount, I think it is designed to hold the motor down when the axle is trying to wind it up. It looks like a straight tension bolt that has been overloaded. With enough torque and enough hard launches, I fear it will fail again.

I'm going to order a new mount and then see if I can figure out a way to modify the mount for a larger fastener.

Oh, Cobb stage 1 OTS tune, K&N filter, Mountune intake hose.

I'm going to check out my CV joint boots too.

 

[twolf]

I seem to have broken my motor mount, the head sheared off.

On the bolt head, it is marked 10.9 so I think it should have been a good bolt.

I broke it being stupid, with sticky tires and a 3,000 rpm clutch drop from a stop.

Looking at the mount, I think it is designed to hold the motor down when the axle is trying to wind it up. It looks like a straight tension bolt that has been overloaded. With enough torque and enough hard launches, I fear it will fail again.

I'm going to order a new mount and then see if I can figure out a way to modify the mount for a larger fastener.

Oh, Cobb stage 1 OTS tune, K&N filter, Mountune intake hose.

I'm going to check out my CV joint boots too.

Please get as much info as you can on this, I'm afraid with enough time mine will break too, and I want to keep the bolt on hand. Someone earlier said it was a stud, not a bolt?

Just to clarify, this is the bolt directly under the coolant res?

 

[dyn085]

I've seen this happen a handful of times on the FiST forums, quite a few more in FB groups, and a couple of friends as well. It's based on a $14k platform so it should be understandable. I already have a spare to put in its place when the day comes.

 

[Kiotofl]

I've seen this happen a handful of times on the FiST forums, quite a few more in FB groups, and a couple of friends as well. It's based on a $14k platform so it should be understandable. I already have a spare to put in its place when the day comes.

My only question is why wait until it shears? Assuming the spare bolt you have is better/stronger. Only reason I'm asking is because I was thinking about getting the bolt replaced right away, but if I don't really "have to", I'd just wait as well.

 

[dyn085]

My only question is why wait until it shears? Assuming the spare bolt you have is better/stronger. Only reason I'm asking is because I was thinking about getting the bolt replaced right away, but if I don't really "have to", I'd just wait as well.

Mostly because of the unknown. For every sheared bolt there are hundreds that haven't so it could be as simple as a manufacturing defect within a small batch. I might never need the spare.

Conversely, there's no way of knowing if there's no manufacturing defect with my spare. I could have a perfectly good OEM bolt that would never shear and replace it with a defective replacement and actually cause myself future issues. Outside of fun modifications, there's never really a point in replacing good parts that haven't failed unless you know 100% that a failure is impending (like a timing belt or whatever).

 

[Kiotofl]

Mostly because of the unknown. For every sheared bolt there are hundreds that haven't so it could be as simple as a manufacturing defect within a small batch. I might never need the spare.

Conversely, there's no way of knowing if there's no manufacturing defect with my spare. I could have a perfectly good OEM bolt that would never shear and replace it with a defective replacement and actually cause myself future issues. Outside of fun modifications, there's never really a point in replacing good parts that haven't failed unless you know 100% that a failure is impending (like a timing belt or whatever).

Gotcha! Pretty new to all of this so I'm taking notes, thanks for the explanation.

 

[Wimp Lo]

The factory part is clearly a bolt. It is marked 10.9 so an upgrade would need to be something special unless the mount can be drilled and tapped for a larger bolt.

One thing I notice is that the factory bolt is threaded nearly all the way to the head and sheared very near the head. It might make sense to replace it with a longer bolt with a bit of shank and trim it to length.

Another idea I have is to get a longer bolt and cut a piece of tube to make kind of a crush washer so when the motor tries to stretch that bolt it crushes the tube instead of popping off the head.

There is the possibility of finding a stiffer hydraulic mount to weld in to the Fiesta bracket or increasing the fastener size in the stock mount but those are both fairly extreme solutions.

 

[Wimp Lo]

I was just looking through the R2 parts manual and it looks like they didn't upgrade that part so we don't have an off the shelf upgrade.

 

[westcoaST]

Typically fasteners of this type fail when not torqued down properly. You can check the integrity of any bolt using either penetrant or magnetic particle inspection, depending on the base metal. You can also replace a steel bolt with a stronger bolt made from ph stainless and order one with a shoulder. Does any one know if these bolts are torque to yield bolts? I'm too lazy to break out my DVD.

 

[Wimp Lo]

I just placed my order for a new mount which seems to come assembled. I still need to order a Helm manual so I don't know if they include a torque spec for that.

I can say that I didn't hear anything before the failure, if it had loosened I think the movement would have been audible. I think it was just overloaded.

If it wasn't a loose bolt causing a shock load or manufacturing defect, there isn't a lot to improve on a 10.9 bolt unless the size is increased. For a small improvement, the hole could be slightly drilled out and tapped 1/2-13, that is not perfect but it should have pretty much full thread engagement for several threads. For a bigger improvement, 9/16-12 or 9/16-18 would allow a clean set of threads if the mount has enough meat. 5/8" bolts might be easier to find and stronger yet but without looking at it I worry about enlarging the hole too much.

There is probably a metric solution but I'm sure I won't have the tap or tap drill and the fastener would be harder to find.

 

[westcoaST]

Yes, you can improve on a 10.9 bolt. You change the base metal, which changes the bolt strength. Take a look at aerospace fasteners like SPS. Also you will not hear a loose bolt if it is not torqued properly, but is still torqued to less than optimum value. Always retorque bolts after you have run your car for a day or so. Take a closeup photo of your broken bolt and I can tell you why it failed. That's what I do for a living.

 

[Wimp Lo]

Well I tried to order the Helm manual but their web site sucks on my phone, I can't add it to my cart. I need to go to a PC to place my order.

 

[Wimp Lo]

I will try to get a nice macro photo for you.

As for improving on a 10.9, I am aware that fancy bolts exist but 10.9 is already very hard metal, increase the strength much more and the elongation is going to be even less.

Also, I am not a fan of metric thread forms.

If I can increase the fastener diameter, get a better thread form and use a more ductile bolt I think that is a better solution than hoping a super alloy bolt isn't too brittle.

That is the way I'm leaning until I can get a closer look at the hydraulic mount.

 

[twolf]

I've seen this happen a handful of times on the FiST forums, quite a few more in FB groups, and a couple of friends as well. It's based on a $14k platform so it should be understandable. I already have a spare to put in its place when the day comes.

It clearly is understandable, hence me trying to get a spare and NOT complaining about it.

 

[dyn085]

It clearly is understandable, hence me trying to get a spare and NOT complaining about it.

Because being afraid that a bolt will fail on a new car is completely normal. Nobody said you were complaining.

 

[Wimp Lo]

I am a little bit disappointed that the bolt wasn't upgraded.

For a manufacturer, changing that bolt would be a $3-4 fix at most. For a Fiesta ST owner that breaks it, that can be a $200+ fix and you still have a weak bolt.

Ford had to look at that mount when they developed the ST because the torque is almost doubled.

Now I'm thinking the first and second gear torque limiting were put in the ECU because the motor mount was weak.

It was a shitty thing to do. I hope I can fix it with a bigger or better bolt.

 

[Chris G]

So who's been replacing their bolt? Just curious...