How to Replace Your Spark Plugs

What You'll Need
New Spark Plugs
Spark Plug Socket (the same size as the spark plugs you are using)
Spark Plug Gap Tool (optional)
Feeler Gauges (optional)
Wire Brush (optional)
Di-Electric Silicone Compound
Thread Compound

Anyone with a car should learn some basic maintenance procedures so that they are safe when driving, this includes being able to change a spark plug. Spark plugs are a vital part of your engine that need to be kept in good condition for your car to work properly.

Changing and cleaning spark plugs can seem like a very difficult and messy project at first. But don't despair, as long as you have the right tools at your disposal you shouldn't have any problem changing and cleaning spark plugs in your car.

Step 1 - Wait

After driving the car, you must wait at least an hour for the engine to cool down before starting work. If you try to work on it while the engine is hot, you are only going to end up hurting yourself.

Step 2 - Open the Hood

Start by popping the hood of your car by using the release catch. Release the bonnet from the catch and support it with the arm under the bonnet.

Many modern cars are just a mass of black plastic boxes under the hood, as these are designed to reduce noise. If this is what you see,  you will need to remove the boxes first so that you can access the spark plugs.

Step 3 - Find the Spark Plugs

The next thing you need to do is locate the spark plugs. Depending on the type of engine you have, the spark plugs will be found in different places. Replacing spark plugs on a V6 or V8 engine will be much more difficult than other types because the space is more restricted.

If you're having trouble finding the spark plugs, look around for some very thick wires known as HT leads. These connect the spark plugs to the distributor cap. Many cars have a rubber plug over the spark plug to prevent moisture getting inside; you will need to remove this first.

Step 4 - Take Off the Leads

You can't simply rip all the HT leads off because this will mess up your engine timings. Each spark plug fires at a certain time, and if you mix up the order of the leads, you will cause no end of problems, including miss-fires. You should prevent this by concentrating o replacing one plug at a time—never take all of the leads off at once.

Step 5 – Remove the Plugs

Once you have uncovered the first spark plug, you can then set to work removing it. Use the spark plug socket and put it over the top of the plug, this should fit securely. If not, then you are probably using the wrong sized spark plug socket. Turn the socket counterclockwise to loosen the old spark plug.

When the spark plug is loose, you should be able to pull it out with your fingers. Depending on the orientation of your engine, this might be slightly more difficult.

Step 6 - Look at the Old Spark Plug

When the spark plug has been removed, you might be tempted to discard it and replace it. However, it's a good idea to actually take a look at the spark plug as it can tell you a lot about the health of your engine. A little soot on the plug is normal, but any oil on the spark plug or a lot of soot can indicate much more serious problems which need your attention. Oil should never be able to enter the spark plugs, and this will only happen if the piston rings have worn or there are other serious problems.

Step 7 – Install the New Spark Plug

Before you actually fit your new spark plug, compare it with the one you just took out. You want to make sure you are replacing like for like wherever possible. Most spark plugs for specific vehicles will already have the correct gap set; if not, you may need to adjust this yourself.

Fitting the spark plug is then just a matter of using your ssocket to tighten the plug and then replacing the HT leads. You will then need to test to make sure everything works correctly.