Glow plugs are crucial components of a diesel engine and are essential for optimal operation, yet they often remain a mystery for many drivers! 

It’s important to keep an eye on your glow plugs to ensure they are fitted correctly and functioning at their best.

From how much does it cost to replace glow plugs to signs your glow plugs are faulty, you’ll find everything you need to know in one place. Scroll down to get in the loop now. 

How much does it cost to replace glow plugs?

The average cost for replacing glow plugs in the UK is £170. 

However, prices can range from £125 to £250 depending on your vehicle's make and condition. These costs include changing all of your glow plugs in one go.

The cost of glow plug replacement varies based on your vehicle and the manufacturer’s recommended parts. Additionally, the type of mechanic—whether a mobile mechanic or a dealership technician—can impact the total cost.

Here’s a quick overview of glow plug replacement costs per car manufacturer:

Your location can also affect the cost of glow plugs. Here are some average costs from across the UK:

What are glow plugs and what do they do?

Glow plugs are heating devices in diesel engines that facilitate starting, especially in cold conditions. 

These metal rods have a heating element at one end, which heats up when the engine is turned on. This warmth helps ignite the air-fuel mixture, essential for diesel engines that require high temperatures for combustion. 

Glow plugs typically operate briefly during startup and shut off once the engine reaches a certain temperature, enhancing efficiency and reducing emissions.

How many glow plugs does my car have?

In most diesel vehicles, there is usually one glow plug per cylinder.

So, a six-cylinder engine would have six glow plugs. However, this can vary based on engine design, manufacturer, and engine size.

Factors like engine size, vehicle model, or modifications can also affect the number of glow plugs.

Always check your owner’s manual for specific information.

How often do glow plugs need replacing?

You should replace your glow plugs every 80,000 to 100,000 miles or when they show signs of failure. Driving conditions, maintenance habits, and the quality of the glow plugs can all impact their lifespan. It's wise to have them checked during regular maintenance so you can drive knowing they’re in tip-top condition!

How do I know if my glow plugs need replacing?

There are a few signs to keep an eye out for when it comes to replacing your glow plugs. These include:

• Difficulty starting the engine — Your engine struggles to start, especially in cold weather or the winter.
• Rough idling — The engine runs unevenly when idling.
• Excessive smoke — Noticeable/abnormal smoke from the exhaust during startup.
• Dashboard warning light — The engine or glow plug indicator light is on.
• Mileage — Inspect your glow plugs if they've surpassed 100,000 miles.

If you notice any of these signs, it’s time to talk to a mechanic. 

With Bumper, you can spread the cost of any repairs at no extra cost. Learn how it works today.

Are there any warning lights for glow plugs?

Yes, as mentioned above, many diesel vehicles are equipped with a specific warning light for glow plugs. This light usually resembles a coil or spiral symbol on the dashboard. 

• Glow Plug Indicator Light: This light turns on while the glow plugs heat up before starting the engine and usually goes off once they’re ready or the engine starts.
• Check Engine Light: If the glow plugs malfunction, the check engine light may also flash up. While there are a few reasons for this light, glow plugs might be one of them. 

Jump to Bumper’s complete dashboard warning light guide now.

How do I check my glow plugs?

Checking the condition of glow plugs in your diesel engine is an important part of regular car maintenance and, luckily, is pretty straightforward.

Before you begin, ensure the engine is off and that you're in a well-ventilated area. This will keep you safe and make the process easier. Follow the instructions below to get started:

• Find the Glow Plugs — Look for the glow plugs near or inside the cylinder head. There will be one plug per cylinder.
• Carefully Remove the Glow Plugs — Use a socket wrench to carefully unscrew and remove the glow plugs without damaging them.
• Clean or Replace — If applicable, wipe off carbon deposits and consider reinstalling the old plugs. Make sure to lubricate them before reinserting.
• Reconnect Wires — Reattach any wires or connectors that were removed. This may not be applicable for some vehicles. 
• Start the Engine — Once done, turn on the engine to check everything is working well. If you see no issues, you’re all set!

Some higher-spec models may come with a special tool for removing glow plugs, so check whether your car needs one.

Keep an eye out for common issues like cracks, wear, or carbon buildup, and replace any damaged plugs as soon as you can. 

Just remember to refer to your car owner’s manual and the packaging of your new plugs for the right settings. When in doubt, always contact a professional for expert advice!

How long do glow plugs last?

Typically, glow plugs will last around 80,000 to 100,000 miles. So, always check them once your mileage hits this range.

The accurate answer depends on your car's make, driving style, and material quality. Check your owner’s manual for answers, or contact the dealership for specific advice. Rest assured, once checked, you won’t have to worry about them for a long time!

Can I drive with faulty glow plugs?

No. Drivers are advised against driving if you suspect you have faulty glow plugs. Doing so can lead to ongoing poor performance, and eventually, your engine may misfire. This poses a significant danger to you and other drivers on the road.

If desperate, you can drive with a faulty glow plug, but it’s best to keep the trip short and head straight to the mechanic.

Conclusion

Hopefully, if you were searching “How do I know if my glow plugs need replacing?” our guide has helped you discover your next steps towards a safer and more reliable vehicle!

How Bumper can help

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