An unusual way to remove a broken hairpin

When removing the head from the cylinder block, broken pins occur. This is a common problem that can be solved in many ways. The easiest way is to use an extractor to unscrew broken bolts, but it doesn’t always help. In this case, you have to knock on the breaker, weld a bolt to it and try to unscrew it. This almost always helps, but there is, albeit small, a chance of breaking the block. If it costs several thousand dollars to replace it, then it is extremely unpleasant. To avoid this risk, you can remove the chips chemically. It is long, but safe.

Materials and tools:

• set of drills;
  
• lemon acid;
  
• dry air heating element 1 kW or more;
  
• dropper;
  
• syringe;
  
• thermostat with remote sensor.

Removing the stud breaker

Using a drill, or better yet a drilling machine, you need to drill the center of the breaker with a thin drill to its full depth.

The hole is then expanded with a larger diameter drill.

It is advisable to make passes with drills with an increase in their thickness by 1 mm.In this case, there is no risk that one of them will break under the load and remain in the stud, which will create many problems. You need to widen the hole until the breaker is completely drilled out and only its thread remains in the block. It is very important not to snag the block threads with the drill.
After drilling, a steep solution of citric acid is poured into the resulting hole. The liquid will evaporate, so a supply of drops is set through the dropper to maintain the given volume of solution.

Simultaneously with the supply of acid, it is necessary to ensure heating of the block. To do this, a dry-type heating element is applied closely to it.

The heating element itself is connected through a thermostat, the sensor of which is lowered into the mounting hole of the adjacent unscrewed stud with oil filled.

You need to set the temperature to plus 80 degrees Celsius, which is completely harmless for the unit. The opposite side of the heating element should be insulated with some kind of blanket so that it cools down longer.

You will also need to cover the cylinders with oiled paper to prevent splashes of citric acid from getting into them, as this will create small potholes on their walls. The block is left in this form for 1-2 days. The less metal from the breakage remains in the block, the faster everything will be dissolved. Periodically, you need to select the acid with a syringe, inspect the hole and fill it with a new solution, as the concentration of the old one weakens.

Having dissolved the chip, you need to refresh the threads with taps. After this, the engine can be assembled. This method takes a long time, but it ensures that the block remains intact. If the chip cannot be removed by other means or the block is too expensive to risk, then this option for solving the problem will be quite acceptable.

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