How to Remove a Broken Spark Plug

If you have tried to unscrew it and it has broken, you will have the lower part (threaded with the electrode) still inside the engine and the upper part (the connection plate) in hand. Do not turn the remaining spark plug in place; it could get stuck worse.

Use a broken spark plug extractor (type spark plug extractor: available on Amazon with code B0995YBWL1 for £29.99). Alternative (if you don't have the extractor): gently tap with a small hammer on a flathead screwdriver inserted into the spark plug hole to create a grip point, then turn.

If the ceramic piece (the insulator) breaks off and falls inside, remove it with long-nose pliers or use an air compressor to gently blow it out (but without pushing fragments into the cylinder).

It’s better to blow and suck. If the spark plug is broken at the base and the threading has come off, this is the worst case.

The spark plug remains in place, but the threaded part is stuck to the cylinder head. Do not attempt to unscrew it with a screwdriver or pliers: you will damage the cylinder head.

Use a left-hand thread spark plug extractor (e.g., Lisle 65600: AliExpress code 1005012287545851 for £41.99). Insert the extractor into the hole, secure it well, and turn counterclockwise with a socket wrench. If it doesn’t come out, heat the area around it with a hairdryer (not with an open flame) to expand the metal.

If it still doesn’t come out: take it to a specialist mechanic – because a broken spark plug may require the removal of the cylinder head. Last case: the spark plug broke before being removed (e.g., ceramic cracked while driving).

If the engine made a "bang" and now won’t start, it’s possible that the electrode has broken and fallen into the cylinder. Do not attempt to start the engine – the piece of ceramic or metal would destroy the piston and the cylinder head.

Remove the broken spark plug with an extractor, inspect the inside of the cylinder with an endoscope (or if you don’t have one, with a torch and a mirror), and if there are fragments: remove the cylinder head. There is no other safe way.