Exhaust heat shield loose - Fixed on Astra H Mk5

Exhaust heat shield rusted itself loose the other day, dropping down and catching on speed bumps. This seems to be a common thing on older cars, which I have done before on my old ford focus. I was intrigued to see how the Astra fittings compared to the focus, so set about fixing it. Looking under the car my initial thoughts were "****! those nuts are never going to undo".

The heat shield is held on by three flange nuts which is not a smart design. The one on the very bottom of the spare wheel well is exposed to the elements, so was all rusty, even the ones shielded by the exhaust were rusty. On the focus they use a metal clip which is a sacrificial part when removing. That design seems better because the thread will remain intact and the clip wont rust solid too it.

Out with the Plus Gas, 10mm socket and spanner. You guessed it that bottom one sheared but the other two surprisingly came off okay. I ended up jacking up one side of the car on axle stands just to gain better access underneath. I un-hooked the two rubber exhaust mounts on the back box which gives you enough room to undo the two heat shield nuts above it.  Picture shows the rusted remains where the thread should be.

Next job is to make some plates to cover the rust holes in the heat shield. You could use washers but finding some that big with a small hole might be tricky. The bean tin is my favourite for this task, cutting out squares then folding over the edges with pliers. The edge folding is essential if you want to avoid finger cuts and makes them easy to handle. You drill a small hole in each plate big enough for the thread to just pass through. Here's a picture of me making the plates.

I drilled a hole into the sheared head and into the spare wheel well to replace the snapped thread. The idea is to use a self tapping bolt and drill a small hole. Don't worry about the thread protruding into the spare wheel well as it's right under the plastic wheel support. Obviously empty the spare wheel well completely while drilling though!

Here you can see the thread from the bolt in the spare wheel well. I covered this in sealant after just to avoid any rust issues. You could do this a few ways depending on what bolt you had handy, it might look better with a bolt going from the inside outwards with a nut on the end. Just depends what you have handy and prefer.

You can just see the top two heat shield bolts in this picture, complete with shiny new plates.

That's how to fix a loose heat shield on a Astra H Mk5. You can go a step further and paint the new shiny metal patches in heat resistant paint e.g. calliper paint. I didn't have time to do that and my focus has been going strong for 2+years with a similar repair, while they have surface rusted they are still solid.

 If you find the above useful or you have other tips when doing this job then please leave a comment. Done a few jobs I need to write up so always good to hear if these have been useful for someone.