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344 posts

Ultimate Geek

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#226182 24-Dec-2017 11:42
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I've just bought a set of Pro Rack roof racks for my 2005 Mazda Premacy. This doesn't have gutters, and so it uses a single screw mounting point for each mount, under some rails on the roof.

 

 

This is a grub screw with a hex bolt at the top.

 

The rest of the mount goes together like this:

 


and

Three out of four of them looked like this,

 

 

and worked fine, but the last one looks like this:

 

 

It looks like water has got in there, and the whole thread is rusted away. I tried putting the bolt in hoping that there would be good metal underneath some surface rust, but the whole thing looks rotten. As far as I can tell, there is not enough good metal remaining to even tap a larger hole.

 

My question is:- does anyone have any ideas as to how I could get the grub screw (or a similar thread screw) mounted securely where the rusted hole was? A friend suggested filling it full of epoxy, but I am not confident in the integrity of the metal around the hole. I thought a bolt with a largish head from the inside of the car would be an option (after taking out the roof lining), with tons of silicon or other waterproofing type stuff. (And yes, I know there will be a general rust problem under that rail...)

 

Does anyone have any brilliant ideas?

 

 


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14462 posts

Uber Geek

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  #1924784 25-Dec-2017 00:32
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So, is that an old bolt which as sheared off and been left in the hole?






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  #1924810 25-Dec-2017 06:54
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That's what it looks like. Similar roof mounts use Rivnuts but the nut on the Mazda seems inserted from below.





 
 
 
 


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Ultimate Geek

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  #1924829 25-Dec-2017 08:24
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Could you get one of the other style mounts and use that instead?
They have a steel belt that wraps around the top of the door frame at the roof, and when tightened with the roof bar they hold tight.

Hmm, what to write...
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  #1924848 25-Dec-2017 09:21
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Use a large drill to remove remains of the old nut (avoiding the roof lining) and attach a new “nut plate” from below. It looks like a nut attached to a plate that has a couple of rivet holes.

Depending on your attachment method (you need to certain the rivets can’t pull out) you might be able to do it from above




Matthew




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Ultimate Geek

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  #1924854 25-Dec-2017 09:45
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Geektastic:

 

So, is that an old bolt which as sheared off and been left in the hole?

 

I'm pretty sure that is not the case - the mounting hole stands proud from the bottom of the gutter, as far as I can tell. The wall of the hole is corroded from both the inside and outside, and is thus very weak.

 

Loismustdye:

 

Could you get one of the other style mounts and use that instead?
They have a steel belt that wraps around the top of the door frame at the roof, and when tightened with the roof bar they hold tight.

 

I would have much preferred this type of arrangement, but the car (Premacy) has rear sliding doors, with nowhere that this type of thing can hook on to.

 

bung:

 

That's what it looks like. Similar roof mounts use Rivnuts but the nut on the Mazda seems inserted from below.


 

I'm not sure, and I haven't yet figured out how to remove the trim so that I can check :)

 

mdooher:

 

Use a large drill to remove remains of the old nut (avoiding the roof lining) and attach a new “nut plate” from below. It looks like a nut attached to a plate that has a couple of rivet holes.
Depending on your attachment method (you need to certain the rivets can’t pull out) you might be able to do it from above

 

This is the type of solution I suspect would be the best, as it would be strong. I'm rightfully concerned about kayaks flying off at highway speeds undecided. As long as I can ensure waterproofing, I'm happy to drill through the outer shell of the car itself if it will ensure strength (12 yr old car, I'm not worried too much about resale value).


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  #1924866 25-Dec-2017 09:59
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In the photo of the good "nut" the edge of the surrounding hole has a crisp edge that doesn't look as if it is in sheet metal. Is it the roof or a plastic spacer?



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  #1924867 25-Dec-2017 10:03
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Bung: In the photo of the good "nut" the edge of the surrounding hole has a crisp edge that doesn't look as if it is in sheet metal. Is it the roof or a plastic spacer?

 

A hard plastic spacer. I've levered up the edge of the trim that runs the length of the roof, and it looks like the plastic spacer is maybe 10 cm long.


 
 
 
 


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  #1924937 25-Dec-2017 11:57
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Will anything from here do?

https://www.ezlok.com

We use the spring type threaded inserts but it doesn't look like there is enough metal left to great into.

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  #1924938 25-Dec-2017 11:57
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Will anything from here do?

https://www.ezlok.com

We use the spring type threaded inserts but it doesn't look like there is enough metal left to thread into.



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Ultimate Geek

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  #1924952 25-Dec-2017 12:05
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JamjarsNZ: Will anything from here do?

https://www.ezlok.com

We use the spring type threaded inserts but it doesn't look like there is enough metal left to thread into.

 

Thanks for the link. I suspect that any solution will have to get rid of the existing Rivnut-type thing, as it is rusted beyond being rescuable...


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  #1924955 25-Dec-2017 12:20
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If the existing hole gets too mutilated to rescue Subaru use a system consisting of a threaded insert in a bracket bolted into rivnuts either side of the insert location. Whatever you come up with use high tensile bolts rather than something from the woodwork aisle.

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  #1924957 25-Dec-2017 12:25
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Drill out and new riv-nut?

 

Places like https://www.fullyequipped.co.nz/locations/ that install canopies (and roof racks) should be able to do it for you really cheap.

 

 


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  #1924969 25-Dec-2017 13:12
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I don't think it's a rivnut, I think it's a threaded boss retained in a floating mount. I'm betting there is a little movement in the good one.

I'd:
Ask Mazda if they have replacements.
Ask a panelbeater or Mazda if they know how the gutter trim comes out (it's bound to be removable, and it's probably what holds the nuts in). Google might know too.

If you can achieve these two things, it'll probably be stupid simple to replace the lot.




Location: Dunedin

 




344 posts

Ultimate Geek

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  #1924998 25-Dec-2017 15:40
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andrewNZ: I don't think it's a rivnut, I think it's a threaded boss retained in a floating mount. I'm betting there is a little movement in the good one.

I'd:
Ask Mazda if they have replacements.
Ask a panelbeater or Mazda if they know how the gutter trim comes out (it's bound to be removable, and it's probably what holds the nuts in). Google might know too.

If you can achieve these two things, it'll probably be stupid simple to replace the lot.

 

Zero luck at searching on Google, until I remembered that the Premacy is sold as the Mazda 5 in the states, and then I found tons of images and guides. It looks like the offending piece is like this:

 

 

Definitely looks like I won't need to drill into the car body itself!




344 posts

Ultimate Geek

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  #1950824 2-Feb-2018 17:29
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Gurezaemon:

 

andrewNZ: I don't think it's a rivnut, I think it's a threaded boss retained in a floating mount. I'm betting there is a little movement in the good one.

I'd:
Ask Mazda if they have replacements.
Ask a panelbeater or Mazda if they know how the gutter trim comes out (it's bound to be removable, and it's probably what holds the nuts in). Google might know too.

If you can achieve these two things, it'll probably be stupid simple to replace the lot.

 

Zero luck at searching on Google, until I remembered that the Premacy is sold as the Mazda 5 in the states, and then I found tons of images and guides. It looks like the offending piece is like this:

 

 

Definitely looks like I won't need to drill into the car body itself!

 

 

Update - after being told by Mazda in downtown Whangarei that a single nut plate would cost $102 and take a couple of months to come from Japan, they suggested a local wrecker, who had a similar (but not identical) part on an Axela. $30 later, and half an hour of fiddling around removing roof liners in the car, this was installed (it fit - just) and it works perfectly.

 

Thanks all for your help - Geekzone never ceases to surprise me at the amount of clever people frequenting here.


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