USEFUL TOOLS
PLUG SOCKET: A spark plug spanner or socket is required to remove and fit spark plugs. There are three common sizes of deep socket, which have enough clearance to avoid damaging the top of the spark plug – 14mm, 16mm and 21mm. Some toolkits include these sockets. Laser Tools’ set of three thinwalled sockets shown here cost £12.50 or less (part number 7295) for the set.
MAGNETIC SOCKET:
Some spark plug sockets have a rubber insert inside to help grip the spark plug when removing and fitting it, but this can fall out. A solution to this potential problem is to use a magnetic spark plug socket, which doesn’t have a rubber insert, although there is the risk of the socket attaching itself to other metal objects.
RATCHET & BARS:
A 3/8in ratchet and a variety of extension bars are useful for accessing, undoing and tightening spark plugs. A larger or long ratchet is not recommended because spark plugs generally should not be too tight when fitted, and too much leverage when undoing them risks breaking them.
PICK-UP TOOL: A magnetic pick-up tool can help to extract a spark plug where it has fallen out of the socket and cannot be lifted out by hand. This can happen if a spark plug socket has a rubber insert to grip the socket, but it has fallen out and remains stuck on the spark plug.
BRUSH: If you want to extract, clean and refit a set of spark plugs, then a soft brush is useful for removing carbon deposits from around the core and electrode. This can help to improve the spark that’s generated. Short runs of the engine can result in the spark plugs being fouled, so cleaning them may help to improve the running of the engine.
FEELER GAUGES: Where a spark plug has a single electrode, it’s worthwhile checking the gap between the base of it and the top of the core. A set of feeler gauges is required for this job. And if the electrode gap needs to be adjusted, use a gapping tool, although we modified a small screwdriver (see inset photo) to adjust the electrode’s gap.
TORQUE WRENCH: Spark plugs should be tightened to a specific torque setting to sufficiently crush a washer on the plug, but avoid over-tightening them as this can damage the thread. In many cases, especially for aluminium cylinderheads, around
30Nm is sufficient torque, but do check your workshop manual.