Broken Bash Plate Bolts; a pain in the bum

A few hundred kilometres up the PDR on the way to Cape York, I peak my head under the Dmax to make sure nothings awry, and notice another missing bolt from our underbody protection. This would be about the 4th or 5th bolt that has either broken, or come loose, and its starting to get a bit old.

I slide under the vehicle, and realise that its snapped off, with the thread stuck in the diff drop, which is a 20mm piece of flat bar, and has almost no access on either end. Lovely.

Bash plates on our Isuzu Dmax
We’ve had a number of these bash plate bolts break

I generally don’t like working on vehicles, and the thought of climbing under the Dmax and working on its lowest point on a sandy beach next to a beautiful creek that I could be swimming in was not overly appealing.

Relaxing at Coen
Relax, or fix a broken bolt under the Dmax?!

Nevertheless, I grab some tools, dig a trench out, lay a tarp down and climb under. I grab my trusty set of Sutton easy outs, and punch a 3mm hole through the middle of the thread, with a left hand drill bit. I up the size to a 5.5mm drill, and then put an ezy out in, and give it a bit of love. Using just a 150mm spanner, I hear a bang, and my ezy out lets go, in the middle of the bolt thread. 

If you’ve never broken an ezy out before, they are almost impossible to remove unless you can break them up, as they are so hard that nothing cuts into them.

I spend the next 2 hours trying to chip it out, drill new holes and eventually slide out, exhausted and in no better position.

After a break, I decide I’m not going to get beaten, and slide back under, with a different plan. I punch a 2mm hole through the edge of the bolt, and make it bigger, and bigger, until I can slide an 8mm bolt through. I struggle to get the washers and nut on, but eventually the bash plate is held in place by a new bolt, and I slide out, feeling relieved.

It’s certainly not as good as it could have been, but in the middle of the bush, with limited tools and a whole lot of corrugations to go, its as good as it could be, and it had to do.

Why do the bolts break?

This is an interesting one, and I suspect its a combination of things. I don’t believe much engineering goes into the development of basic, pressed bash plates, and its likely that when the chassis flexes (and it does), it puts sideways stress on the bolts, and they break.

If the bolts were through holes and had nuts it would be less of an issue, but many go into the factory (or aftermarket in the case of the diff drop) tapped holes, and that’s a much bigger problem.

It was suggested that running grade 8.8 bolts isn’t a good idea on this sort of application, and that might be part of the problem too.

Jardine River Ferry Gravel road
Our Dmax has been all over Australia, and gets well used

Have you had issues with bash plate bolts breaking on your vehicle?

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