How Much Does Glow Plugs Replacement Cost in the UK?

Glow plugs are used to preheat the air in the combustion chamber of a diesel engine to aid cold starting and during DPF regeneration. They are most commonly used in cold weather, or when the engine has been sitting for a while and the cylinders have had time to cool down. Glow plugs fail over time and typically need to be replaced every 50,000-100,000 miles or every five years.

How much does it cost to replace glow plugs?

The average cost of replacing a diesel engine glow plugs is £170, with prices ranging from £125 to £250 with pressure sensing glow plugs costing more. These prices include the cost of replacing ALL glow plugs in a vehicle. Due to their small size, glow plugs that have seized in place are susceptible to breaking. In such a case the cylinder head would need to be removed which is an additional cost to consider. The exact price of glow plug replacement depends largely on your car and the parts recommended by the manufacturer.

Your location can also be a key factor in determining the price of glow plugs replacement. For example, average hourly labour rates and demand in cities like London is around £50-£100 while in towns with lower demand, the labour rates can range from £35-£50. The type of mechanic, for example, a mobile mechanic vs a dealership garage technician can also affect the total cost of glow plugs replacement.

Average cost of a glow plugs replacement by location

To avoid having car owners overpaying and get a fair price for glow plugs replacement, we use real-time data of thousands of car makes and model data, local labour prices for glow plugs replacements and part prices to provide an instant fair quote. Simply enter your vehicle registration number and postcode to get an instant price for glow plugs replacement for your car.

Average cost of a glow plugs replacement by manufacturer

Signs your glow plugs need to be replaced

• Hard to start the engine (especially in cold weather)
• Excessive fuel consumption
• Glow plug warning light flashing when the ignition is switched on
• Engine misfiring
• Rough idling
• Dark or black smoke from exhaust
• Check engine light on

Engine is hard to start

If your glow plugs are faulty, you may have difficulty starting your diesel engine, especially in colder weather. In some cases, this can also be caused by a problem with the car's battery or fuel system but if you experience this symptom along with the glow plug warning light on the dashboard then it’s quite likely you’ll need to get the glow plugs checked and replaced.

Engine is misfiring or low acceleration

A diesel engine misfires with faulty glow plugs because the plugs are not providing the proper amount of heat to the air/fuel mixture in the cylinders. This can cause the mixture to be too cold and not ignite properly. This is sometimes accompanied by reduced acceleration or lower engine performance.

Black smoke from exhaust

The black exhaust smoke is caused by incomplete combustion of the fuel. This can be due to a faulty glow plug, which means the fuel is not getting hot enough to ignite properly.

Frequently asked questions about glow plug replacement cost

Can you drive with faulty glow plugs?

The car will likely have trouble starting or will run rough with faulty glow plugs. So while the car is still driveable, continuing to drive it around can cause some level of damage to the engine. If you notice the glow plug fault warning light on the dashboard, it’s highly advisable to get a diagnostic check to find out what’s the cause and how to get it fixed. In some cases, it can be an issue worse than just a worn out glow plug so it’s best to address the issue when it first pops up to avoid further repair work.

Is it worth replacing all glow plugs at once?

While not mandatory, it is recommended to replace all the glow plugs when one of them fails. Once one glow plug is found to be faulty the others are most likely not too far behind. The standard glow plugs are not very expensive (around £15-£20) so it also makes economic sense to get a mechanic to replace them all at the same time.

Can a faulty glow plug damage the engine?

While faulty glow plugs do not generally cause immediate engine damage, they are used as part of the DPF regeneration process and can put additional load on the combustion process resulting in hard starting and misfiring. This will add strain on the various components of the engine causing expensive damage.

Are faulty glow plugs an MOT failure?

If the glow plug warning light (coil-shaped symbol) is flashing on the dashboard then it will result in an MOT failure. However, if the weather is cold, the glow plug light will light up and should turn off after a few minutes - in this case, it will not result in an MOT failure.

Keep in mind that faulty glow plugs can also cause misfiring which can lead to increased emissions - this can also result in an MOT failure.

What is the difference between spark plugs and glow plugs?

Spark plugs are used in petrol engines to create a spark that ignites the fuel. Glow plugs are used in diesel engines to heat up the air in the cylinders to an igniting temperature (500-600 degrees Celsius).

How long does a glow plugs replacement take?

On average, glow plugs replacement times can range from 1 to 2 hours with an average of just over 1 hours. The time that the job takes will depend on a number of factors, like your vehicle's make and model, year, as well as other factors. Select your car at the top of this page for information on job time and cost for your vehicle through ClickMechanic.

Can I carry out a glow plugs replacement myself?

Replacing glow plugs requires knowledge of automotive repair especially of diesel engines and their intricate ignition systems. Additionally, glow plugs are connected to the vehicle’s electrical components so there is a safety risk involved.

Unless you are a qualified mechanic with the required skills, training and equipment to do the job, we strongly recommend that glow plug replacement is only carried out by a professional mechanic. ClickMechanic can help get you a vetted and local mechanic to carry out the work. Just enter your postcode and your car's registration number at the top of this page and select the work needed to get an instant fixed price up front.

What else could be the problem if my glow plugs aren’t broken?

If you're experiencing issues with your diesel engine that seem similar to glow plug problems but have confirmed that the glow plugs themselves are not at fault, it could be one or more of the following:

• Fuel injector/ fuel filter - if the injectors are clogged or contaminated then it could adversely affect fuel efficiency
• Mass airflow sensor - irregular air-fuel mixture caused by a faulty MAF sensor can cause rough idling
• Dirty air filter - clogged air filter will often mean incomplete combustion which can cause a dark smoke from the exhaust

What happens during glow plugs replacement?

• The mechanic will pre-soak the glow plug threads with penetrating oil or similar and wait for it to take effect.
• Mechanic will then ease the glow plugs undone and remove them one by one
• New glow plugs will then be installed
• Engine start up will be tested and error codes cleared down