CAR’s guide to removing glow plugs

Our guide to DIY diesel maintenance, with a shortlist of the best glow plug removal tools.

A mechanic works on a diesel engine

by Ryan Gilmore |

There isn't the same romance with diesel engines that is given to petrol ones. People will swoon over a Toyota 2JZ or BMW S70 but not so much over a PSA XUD. But diesel engines are still excellent for certain jobs. The efficiency offered on motorways is unmatched and they tend to be almost indestructible. But even the toughest diesel engine needs some basic maintenance and one of the simplest thing you can do is changing the glow plugs.

You can quite easily book your car in with the local mechanic and pay for someone else to do it. Or you could give it a go yourself and save yourself a chunk of cash. We've found everything you could possibly need to change even the most stubborn of glow plugs right here.

If you're doing a glow plug change, it may also be an idea to clean your diesel injectors and top up your engine oil.

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What you need to know about glow plug removal tools:

How do I change glow plugs?

One: Disconnect your battery and locate your glow plugs. Remove the glow plug wires from the glow plug. This will be done by removing a small nut that sits above the glow plug. Do this for each glow plug.

Two: Remove the glow plug using your chosen tool (make sure you use the right size). If you find them to be overly stubborn then you may need to purchase some lubricant or a kit designed to remove damaged glow plugs.

Three: Once all of your glow plugs are out you'll be wanting to clean away the deposits. Using a glow plug reamer or aperture cleaner, clean the glow plug hole but be careful not to damage the threading. Also clean the electrical contact point, removing any dirt that has built up.

Four: Using the socket set, install the new glow plugs being careful not to over-tighten them.

Five: Reconnect the glow plug wires and the nut using a wrench. Finally, you can reconnect your battery and you're ready to go.

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What if my glow plugs are stuck or stubborn?

There are two main reasons why glow plugs can be a pain to remove; age and damage.

If you know the glow plugs haven't been changed in a long time or the car has been idle for an extended period then in most instances, it should simply be a case of spraying some lubricant on your glow plugs and then using a regular glow plug removal tool.

If they're broken on the other hand then it can be a tricky affair to remove them. It is incredibly easy for a glow plug to become damaged when being installed. Over-torquing them can strip the threads effectively locking the glow plug in place and in extreme cases, it can even damage your engine block (a very costly affair). Thankfully, there are glow plug removal kits that will help get these glow plugs out without causing more damage.

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What are glow plugs?

Two different glow plugs
©Photo: Getty Images

Glow plugs provide heat to diesel and air in the cylinder to create the most efficient combustion. For every cylinder your car's engine has, it will have one glow plug and they can be located above the cylinders. They should be fairly easy to find but if in doubt, look in your car's handbook for their exact location.

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Glow plug sizes:

The standard sizes for car glow plugs are; 8mm, 9mm, 10mm, 11mm and 12mm. Check your car's handbook to find the size your car uses and then find a glow plug removal tool that fits your glow plug.

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