What Size is a Spark Plug Socket, Spanner Or Wrench?

Spark plugs are part of the ignition system of a car. They’re connected to the engine’s ignition system and can be easily removed.  It’s the job of the spark plug to generate the spark, so they need to be changed regularly to ensure that your engine continues to run smoothly. While replacing spark plugs, it is important to determine the size of a spark plug socket to ensure that it is fitted snugly into the socket and generates the sufficient spark required for the combustion.

The most common or standard size of a spark plug socket, spanner, or wrench is 5/8 or 13/16 inches. On some older cars, you will also find an 11/16″ spark plug size. However, in modern cars, 14 mm (9/16) and 16 mm (5/8″) are the most spark plug socket sizes. On European engines, you can bi-hex 14 mm spark plug sizes. Sometimes, you might encounter bihex or 12mm hex spark plug socket sizes, but they’re not common. Access to the spark plugs varies enormously among vehicles. Some can be changed in minutes. Others require the removal of the upper intake manifold or other components to access spark plugs.

‍What is a Spark Plug Socket?

A spark plug socket is a tool used to tighten and loosen spark plugs. The spark plug socket is designed to fit into the threads of the spark plug. Spark plug socket performs two purposes:

  • Being long enough to fit the spark plug /not damage the ceramic insulator
  • Holding the spark plug during removal/insertion so it doesn’t just fall out of the socket.

If a spark plug socket slips off sideways, it can break the ceramic top of the spark plug. That’s why spark plug sockets have a rubber insert or grommet to protect the top of a spark plug from damage while installing it in the engine, and to grip the spark plug.

Rubber insert in spark plug socket to protect the ceramic coating on the spark plug

However, in some engines, you may have a hard time pulling the spark plug out as it will slip out of the socket. In such cases, a deep spark plug socket with a magnet inside is to get the plug out because the rubber bushing inside the socket often slips out of the socket and stays on the spark plug.

Magnetic bushing in spark plug socket to grip the spark plug

Spark plug sockets have a type of ‘deep well chrome-plated sockets’ to reach the bottom of a seated spark plug. Deep sockets have a length of more than 50mm. Deep sockets are used for spark plugs for a little extra reach or extra grip over the spark plug’s porcelain to easily remove and fit the spark plug.

Since you’re using an extra grip because of a deep chrome-plated socket to replace the spark plug of a car, it will easily remove the spark plug with the help of a torque wrench or a ratchet.

Keep in mind that deep sockets are not considered standard toolbox items. Spark plug deep sockets are often available in smaller sets or as individual attachments. Moreover, deep sockets do tend to cost more if bought separately due to the increased material used to make them and the lower production volumes.

A spark plug socket can also be bi-hex or single hex. A bi-hex spark plug socket is identified by the 12 points inside the socket, while a single-hex spark plug socket has 6 points. So, depending on the type of your vehicle’s spark plug, you can either use a bi-hex or a single hex spark plug socket.

bi-hex and single hex spark plug sockets

In the figure above, I have shown the schematic of bi-hex and single-hex spark plug sockets. ‘S’ shows the desired spark plug socket size, which is in either in mm or in inches.

If you want to buy the best spark plug socket set, you can get this one by SK. If you want to get a 5/8 spark plug socket, get this one. Here is a link to get a 13/16 spark plug socket.

What Size is a Spark Plug Socket?

The size of a spark plug depends on the make, model, and specific engine. Small engines, such as lawnmowers or motorcycles. The spark plug socket size for lawnmowers can be 5/8,13/16, or 3/4 (19mm) of an inch. On Nissans, the size of a spark plug is either 5/8″ or 5/16″. A small portion of the outer body of a spark plug socket is also hexagonal-shaped to afford the option of using a wrench to turn the socket, as well as a 3/8 internal square to accept a ratchet or torque wrench. 

square hole in spark plug socket for torque wrench

For some engines, where it is difficult to remove the spark plugs from the tight, compact, or bizarre places, a spark plug swivel socket is used to get an easy spark plug replacement. Such sockets allow you to turn the wrench on one axis and convert this motion into a rotation around another axis. I like the GEARWRENCH SPK6 set of swivel spark plug sockets.

Using Torque Wrench for Spark Plug

The manufacturer recommends certain torque to apply to a spark plug so that over-tightening does not damage the plug or the threads in the cylinder head while loose plugs can just come off after a few uses. Generally, spark plugs require a low torque level. It usually requires 7-20 lbs of force. The torque wrench has a gauge on it that displays the torque you’ve applied when turning the wrench.

If the spark plug is too loose, it can cause the following problems in the engine:

  • Pre-ignition problems
  • Misfires
  • Slow accelerations
  • Vibration inside the spark plugs
  • Trouble starting the engine
  • Tickling noise

Gap Setting of a Spark Plug

While installing a spark plug, a reasonable gap between the ground electrode and the center electrode is necessary as it directly affects the nature of the spark generated by the spark plug.

If the gap is too small, there won’t be enough room for the air-fuel mixture between the ground electrode and center electrode. So, when a spark plug fires, there won’t be any spark. Similarly, if there is too wide a gap between the electrodes of the spark plug, the spark will be too weak and there won’t be sufficient heat to ignite the air-fuel mixture in the combustion chamber of the engine. 

Now, modern spark plugs come pre-gapped from the manufacturer. You can use a feeler gauge between the electrodes of a spark plug to determine the gap. For most cars nowadays, 1-1.2mm (0.05″) is a reasonable gap in the spark plug. For older cars, it is .030″ to .035″.

What Size Is A 14mm Spark Plug Socket?

14mm spark plug socket has a size of 5/16 inches.

What Size Spark Plug Socket For F150 5.4?

For Ford 150 5.4, 9/16 spark plug socket size will work. Apart from the size, the wall thickness of spark plug sockets also matters. If the spark plug is close to the walls, the socket should be thin enough to fit in the cylinder head and reach the end of the spark plug. The GEARWRENCH spark plug sockets I linked above are also thin-walled. You can also buy this spark plug socket by Ford.

To remove the spark plug from F150 5.4, you have to remove fuel injectors first. Each spark plug has an ignition coil.  Remove the coil screw and pull the coil boot off the plug. Use a 9/32″ (7mm) socket, extension, and ratchet to remove the coil.

Each spark plug hole in Ford F150 5.4 is about 7″ deep. Remove the spark plugs using a 9/16 swivel socket with a long extension and torque wrench. The new spark plugs should be tightened to 13 lb-ft. Set the gap on the new spark plugs to from .052-.056″. 

Nissan Spark Plug Socket Size

The spark plug socket size for Nissan is either 5/8″ or 9/16″ (14mm), depending on the year, model, and trim level. As the user says:

“Just did a 2015 Versa 1.6 today. It was 9/16″ or 14mm. 5/8″ wouldn’t even fit in the hole.”

You can check out the below video to remove the spark plug in Nissan vehicles.

What Size Socket For Honda Lawn Mower Spark Plug?

The socket size of a Honda lawnmower spark plug is 13/16″. The gap in the Honda lawnmower spark plug should be 0.028 to 0.031 inches.

Do I Need A Special Socket Set To Remove Spark Plugs, Or Will Any Socket Set Work?

A spark plug socket is a deep well socket having rubber or magnets in the end to hold the spark plug. But as far as the size of a spark plug socket is concerned, they are universal and have a common size. However, the material quality of a spark plug socket varies from one brand to the other.

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