Diesel engines have a number of advantages over petrol engines, but they also require their own special parts and maintenance. When a diesel engine fails, it often results from bad glow plugs. Similar to petrol engine spark plugs, glow plugs assist diesel engine cylinders in the combustion process. Rather than using an electrical spark, glow plugs have heating elements that gradually heat up and help drive the cylinders. These heating elements are quite delicate, so knowing how to use special glow plug extraction tools plays a crucial role in successful glow plug removal.
Remove the sensor wires attached to the glow plug sensor connectors with an 8 mm (3/8 inch) spanner. The nuts holding the sensor wires in place are extremely small; don't forget to collect them during removal.
Unscrew a glow plug head with a 10 mm or 12 mm (25/64 or 15/32 inch) deep socket installed on a socket driver, depending on the size of the glow plug, until you have exposed all the threads.
Spray the glow plug with penetrating oil.
Close a 10 mm or 12 mm (25/64 or 15/32 inch) split nut around the base of the glow plug thread, and hold it in place with a 10 mm or 12 mm (25/64 or 15/32 inch) spanner.
Install a spacer from the glow plug extractor set between the split nut and the cylinder head. The spacer will provide a base for the plug during extraction and prevent the glow plug from breaking off in the cylinder head.
Unscrew the glow plug with a 10 mm or 12 mm (25/64 or 15/32 inch) deep socket while holding the split nut in place at the base of the glow plug with a 10 mm or 12 mm (25/64 or 15/32 inch) spanner. Unscrew the glow plug until you have completely removed it.
Repeat this process with all glow plugs.