How can we help?
Glow Plugs Replacement
Typical Cost: Medium
Mobile Repair? Yes
Typical Lead Time: 24 - 48 hours depending on part availability
What do glow plugs do?
Glow plugs were originally used to assist with starting diesel engines in cold temperatures when the heavy oil used to coagulate. Now that diesel has many additives to prevent this, glow plugs have taken on the role of heating the incoming fuel / air mix to provide greater efficiency while the engine warms up. This also assists with decreasing the noise during cold running.
How do glow plugs work and what are the components
Each cylinder will have its own glow plug, controlled by a glow plug relay (or by the vehicle's body computer module (BCM). When the ignition is initially switched on, a current is automatically sent to the relay to switch the glow plugs on. When the plugs are going through this cycle, normally the dashboard will show the pre-heat plug warning, which looks like a coil of wire. Once the glow plugs have heated up, the light will extinguish. Ideally, the engine should only be started once this light has gone out to provide their maximum effect.
Some newer cars, especially this with automatic stop/start systems have special glow plugs with pressure sensors in them. Normally, glow plugs are relatively inexpensive, ranging between £20-£30 each, however the pressure type can be at least five times this.
Typical symptoms that require the glow plugs to be replaced.
You may experience some of the following symptoms
- Glow plug warning light flashing when the ignition is switched on
- Engine management warning light (EML) lit
- Struggling to start from cold
- Excessive fuel consumption while the engine warms up
What happens during the glow plugs replacement?
Changing glow plugs pads is a routine repair for all mechanics and can be done both kerbside as well as in the workshop, providing it is safe to do so.
Whilst there are variations between manufacturers, the basics are pretty similar.
The mechanic will;
- Pre-soak the glow plug threads with penetrating oil or similar and wait for it to take effect.
- Ease the glow plugs undone and remove them one by one
- Install the new glow plugs
- Go through the engine start up routine and if all OK, clear the error codes down
Please note
Glow plugs are notoriously difficult to remove in some circumstances.
As the plugs themselves are around the size of a pencil, glow plugs that have seized in position are susceptible to breaking. Should this occur, there could be a danger that the cylinder head would need to be removed in order to extract them.
Whilst the mechanics will endeavor to do their best to replace the plugs without this occurring, should it happen, the subsequent removal work will not be covered financially by the mechanic.
If you are in any doubt about having the glow plugs replaced by ClickMechanic, please contact us prior to booking.
What does this repair cover?
Unless otherwise stated, the quote for your glow plugs to be replaced will cover;
- The cost of the glow plugs and penetrating fluid
- Coming to you
- Fitting of the parts
- Disposal of the old parts (unless you request to keep them)
- VAT (if applicable)
- 12 months parts and labour warranty
What to search for on the ClickMechanic site?
Glow plugs replacement (all)
Associated repairs
Glow plug relay replacement
How much does it cost to have the glow plugs replaced?
The cost of replacing the glow plugs depends on your car and what parts your car's manufacturer recommends.
Find out what you could save by visiting ClickMechanic
https://www.clickmechanic.com/bookings/car
FAQ’s
Can I supply my own parts?
No, we will not fit customer supplied parts unless they are a brand new item, purchased from a dealership with the receipt as proof of purchase. There is no flexibility over this due to insurance and warranty issues.
What happens if the mechanic finds that the glow plugs do not require changing and the problem is due to another issue?
In this scenario, the mechanic will provide a no obligation quote for the correct repair. Should you accept this, the mechanic can alter the booking accordingly. If you decide not to go ahead with the alternative repair, the mechanic can change the booking to a call out and diagnostic booking and charge according to the time spent with the vehicle and call out.
What happens if a glow plug breaks during the replacement?
As the plugs themselves are around the size of a pencil, glow plugs that have seized in position are susceptible to breaking. Should this occur, there could be a danger that the cylinder head would need to be removed in order to extract them.
Whilst the mechanics will endeavor to do their best to replace the plugs without this occurring, should it happen, the subsequent removal work will not be covered financially by the mechanic.
Can I do anything to reduce the risk of a glow plug breaking during the replacement?
Yes you can! Even a liberal spray around where the plug screws into the engine with something WD40 the day before the booking will all go towards helping them come out.
I have a broken glow plug from a previous attempt to remove it, can ClickMechanic help?
Sadly not. This is an engineering task that not many mechanics will undertake and we are unable to price it with any accuracy.
How do I know which type of glow plugs I have, sensor or normal?
In most cases where the vehicle has the automatic stop/start feature, you will have at least one or even all four sensor type. If we believe your car is fitted with them, you will only be able to request this repair by completing the online manual quote request form.
My glow plug warning light is flashing, does this mean the glow plugs need changing?
No necessarily, the flashing symbol while running is used by some manufacturers as an additional engine fault warning light, so you need to have a diagnostic check done first.
If you have a Ford or Jaguar X-Type, if you get this occur, it is usually a low fuel pressure warning light and that is actually more likely to be the injection (or high pressure) fuel pump failing.