1. We pulled back the exhaust manifold to find a broken stud.

Exhaust leaks can be a dangerous Grim Reaper when driving long distances.

When a 4WD is moving forwards it creates a low pressure area right behind the vehicle. This low-pressure area can draw fumes into the cabin of the vehicle, where carbon monoxide can slowly poison the occupants in the vehicle. That’s why we take exhaust leaks so seriously.

Broken bolts are one of the worst things to deal with as a mechanic. There is definitely an art to extracting them.

The other day we had a GQ 4.2l Diesel Patrol come in for service. We always test-drive a vehicle before we service it and straight away I noticed an exhaust leak when accelerating.

Sometimes you can simply tighten the manifold and reseal the gasket but this one had been blowing for quite some time and we chose to do it properly and remove the manifold for a closer inspection.

Once removed, we found there to be a stud completely missing, and another broken stud in the front of the cylinder head.

2. It’s important to centre punch the broken stud in the middle in case tapping is required.

The fun part of any job like this is working out the best way to extract the broken bolt. Exhaust studs are the worst as they tend to almost crystallise as they are always getting hot which makes them really hard to drill.

Once we have drilled a large enough hole we will always try an ‘Easy Out’. An Easy Out is a tapered bit that, when twisted towards the left, will catch and lock itself into the hole in the stud and twist the broken stud out.

When using Easy Outs, you really need to be gentle with them. As you can see in our photos, we did get the stud in the cylinder head out with an Easy Out so it’s proof they work.

3. In this case we were able to remove the stud with an Easy Out.

The flange stub that broke on us was a bit different. We tried the Easy Out on it and it wouldn’t budge. We actually needed to tap out the threads on this one. This is why it is so important to centre punch and start the drilling in the centre of the stud.

We used a few different sized drill bits until we could get the hole drilled as close to the thread in the manifold as possible without actually damaging the thread with the drill bit. Then with a set of taps you start to tap out the thread.

4. We were left with no choice but to drill out the stud so we could then run a tap through it.

Once we had removed the broken studs and fixed up the threads we fitted new studs and then reassembled the exhaust system.

With every broken bolt removal, we breathe a heavy breath before we start, and when we finish we breathe a huge sigh of relief.

5. After removing the broken stud, we were able to fit up a new stud to the exhaust manifold flange.





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