Stripped captive nuts

[BarnyE]

Out of the four bolts that hold the front gearbox mount to the crossmember, two of the nuts are stripped, the bolts slightly catch then go loose again. I only realised today when I was under my van doing something else and noticed two, on the same side, were loose! Then realised they don’t tighten!

What are my options?


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[Robsey]

The easiest is to get a 'Heli-Coil" thread repair kit.

I have used them for donkey's years to repair stripped threads in alloy castings.

The last time was to replace the M8 thread for the hydraulic clutch slave-cylinder steady-bar on my old DT gearbox.









I hope that helps...

[silverbullet]

Do your homework before using a helicoil type kit! Use appropriate length inserts (expressed in multiples of diamater i.e. 1D, 1.5D etc)
When the coil is fitted it in this sort of situation it should be a half turn short of the total hole depth at each end, under flush for two reasons:
It stops the coil ends lifting and trying to lock the bolt, it also enables the installation tang to be safely knocked off with a punch, again without lifing the last turn which could create a self-locking action.
To shorten a helicoil, remove one coil at a time by gently separating the wind with an old flat screwdriver or flat blade and grind through the wire. Don't use side cutters as it distorts the wire section and the bolt may seize.
Always remove the installation tang!

[Aidan]

check the captives are stripped not the securing bolts - have come across it on one Syncro van, the bolts had lost thread at the vital point, no all of it but enough to prevent them tightening - cleaned the threads in the chassis with a tap , replaced the bolts with genuine used ones and it was ok to torque the bolts up - also make sure the washers are the thick ones
I prefer Timeserts to helicoils personally, but much more expensive kit to start with

The other option is to open the floor above the crossmember and weld in new captives, depends how rusty it all is and state of van, bare shell or built camper, access etc..

[Robsey]

Maybe I am OCD or something,
but due to the age of the old bolts when I drooped out my box,
I replaced them all with new bolts of the same hardness rating and the same length.

The old "penn'orth o tar" idiom comes to mind.