Not sure if this has been covered in detail before, so decided to document my repair process for others to use. I know there is plenty others that suffer this sheared bolt issue.
There is a couple of repair techniques that I know of, either re-tapping or the fitting of a Riv nut. I opted for the latter and this option was very successful. I am not saying this is the best option, just the one I chose.
A common issue from what I can gather. Either N/S or O/S bolts sheared after seizing.
Here we have very little room to work so the windscreen wipers need to be un-bolted and the 3 torx screws securing the scuttle panel removed. Disconnect the washer tubing. Lift off the panel to open up the working area.
Next, from the position of the windscreen wiper arm on the left hand side it will prohibit getting to the rear sheared bolt. You could drop the bracket off by removing two 10mm bolts, but I opted to simply operate the wipers and stop them in a different position.
Now we have opened up the working area, we can see what we are up against. The bolt has sheared off cleanly. We now need to centre punch the middle of the sheared bolt to prevent the drill from slipping. Lubricate the other bolts with generous amounts of WD40 or similar product.
At this point i tied up the bonnet and suspended it from a rafter in the garage. When you undo the bolts on either side the bonnet then hung safely for removal.
If this is not an option then you would need a hand to hold the bonnet whilst the bolts are loosened.
Remove the bonnet completely and store safely.
I opted to use a right angled drill adaptor. These are relatively cheap on eBay or hardware stores.
Using a 2mm drill bit, drill a small pilot hole through the middle of the bolt.
Gradually increase the size of the drill bit to open the hole up. To use a 6mm Riv Nut, I needed to drill out to 9.5mm.
Use a cutting fluid to keep the drill temperature down. I used Rocol
Once the hole has been drilled to the correct size, clean the face of the hole by filing any burrs away.
Using the Riv Nut gun, load up the 6mm fitting and slot inside the hole. Let the tool do its work and voila.....
Next up I picked out some new S/S fittings with new washers and coated the threads with some copper slip to prevent the buggers from ever seizing again!
Refit the bonnet and tighten the bolts.
Refit the scuttle panel and re-connect the windscreen wipers. Jobs a good'un! I took the opportunity to fit my new Auto bonnet in the process which is why its changed colour from Blue to Black!
Next stop...the paint shop!
Hopefully someone will find this useful.
And finally, a pic of the tools that I used to complete the job.
Edited by scottbarton, 02 February 2013 - 09:09 AM.