Engine: 70 T5: Broken cylinder head bolt - successfully extracted

[Distendo]

This is a 'How I did it' piece. It may be far from original, but I didn't find any applicable advice when I was wondering what to do. Anyway, it'll bear repeating.

One of the last cylinder head bolts to be slackened off snapped on initial turn, leaving a 35mm-long stub in the cylinder block.

The top of the remaining stub was 50mm down inside the bolt hole in the cylinder block.

Since all the other bolts came out really easily after slackening off, I didn't think this one would be rusted in or anything serious: I reckon the cylinder head rising a little when the other bolts were slackened off put so much pressure on its thread that it simply couldn't turn. Nevertheless, I thought it advisable to squirt some penetrating oil down there while I was figuring out my next move.

I thought it probable that a left-hand (counter-clockwise) drill, once it was in, might actually turn it out without needing an extractor.

My main problem was how to ensure the drill would be vertically dead-centre to the stub: didn't want to risk drilling off-centre or at an angle and possibly damaging the screw thread in the block. Little chance of using a center-punch when you can't see to position it accurately.

So...

The bolt hole is just over 14mm diameter. I bought a short length of 14mm diameter mild steel bar, and cut two 30mm or so lengths. Using a drill press, I drilled a near-as-dammit dead centre 3mm hole through one, and a 5mm (using the left-hand drill) through the other (stub and bars.jpg).

To ensure the holes would be vertical through the bar (and so vertical into the stub) I first drilled a 6mm hole at the join between the two closed metal jaw faces of a drill press vice (vice jaws closed.jpg). When opened, this provided vertical channels to hold the bar exactly vertical to the drill (vice jaws open.jpg).

I then dropped the 3mm-hole piece into the bolt hole, and drilled through it to make a centered pilot hole in the stub. This was with a right-hand (clockwise) drill.

I'd checked the depth of the bolt hole: there'd only be a 6mm gap between the bottom of the stub and the bottom of the bolt hole, so if the stub turned, it wasn't going far down.

Once I'd made the 3mm dia (approx 12mm deep) hole in the stub, I removed the bar and swarf using a magnetic probe, then dropped the 5mm hole bar section in.

As I'd hoped/anticipated, the left-hand drill turned the stub itself, which came out sweet. Extracted bar, stub, and remaining swarf with magnetic probe.

[SteveSarre]

Hi Distendo,

Must have been sickening when it snapped, but with care and patience you overcame what could have been a disaster.

Good job.

Steve

[Distendo]

Cheers, Steve!

That bit went ok, but I'll only be thinking 'good job' when I hear it start again...

(I say, "when"... Currently awaiting Volvo parts from Sweden. Began the job in a mini-heatwave, I'll be finishing in winter. Possibly...)