Stud extractors – my last hope!
These are specifically designed for a job of this nature. The bolt was originally an M8 stud, meaning it should be 8mm diameter at the outside of the threads. Other sage, beardy and wise forum members recommended the Teng 2300 Stud Extractor (below), which was claimed to work down to 5.5mm and was self-tightening. However, it was clear that we had lost so much of the body of the studding through rust and my other botched attempts that there wasn’t enough left for the stud extractor to grip onto.
I next purchased the Laser Tools Impact Stud Extractor Set, with the larger extractor operating between 6mm and 12.5mm (and therefore, presumably, no good for our purposes) and the smaller operating between 2mm and 7mm, which I thought had to work in our case. The idea behind these is to use the body of the extractor to tighten it onto the stud (much as you would tighten a drill bit into a drill) before applying a wrench to the back of the unit to extract the stud. The ‘impact’ part of the name suggests it can be used with an impact driver, which I don’t own. Nevertheless, it was all very good in theory.
The larger of the Laser extractors slipped, as we expected – and the smaller one required the stud to be longer in order to lock on to it. So it was back to the drawing board!
I was beginning to lose hope, and started looking seriously into the grim possibility of taking the head off an otherwise fine engine in order to drill out the remaining thread. However, I tried one more tool, sourced from the lovely people with all the toys at Axminster Tools & Machinery.
Irwin Power-Grip stud extractors are reverse-fluted to lock onto the thread and drag the studding out, and are claimed to require very little visible studding. This was my one last-ditch attempt at getting the studding out, so I heated it up again for a long period and then doused it one final time. I then put the stud extractor on a socket extension and bashed the smallest one onto the stud with the side of my hammer. I gently increased the torque, feeling the extractor biting down hard into the steel of the stud… and, slowly but surely, felt movement beginning. I was anxious as to whether it was just my last remaining studding shearing away from the block but I continued on, a fraction of a millimetre at a time. To my immense relief, I noted fresh studding emerging from the head as the bolt finally gave way and came out.
From the picture bottom right, you can see just how deeply the extractor had dug into the studding. It was with much relief that I was now able to move on beyond this one, small, broken bolt. I purchased new bolts and a new gasket and reattached the exhaust elbow, this time ensuring that I applied liberal amounts of copper grease so that the next time I need to inspect the elbow it won’t cause quite so much heartache!