NGK GLOW PLUGS

Metal rod glow plugs are equipped with a heating coil in a glow rod made of heat-resistant metal.
A specific material – magnesium oxide – in the interior of this glow rod, protects the heating coil from vibrations and shocks. Magnesium oxide is also an outstanding thermal conductor. This is why the heat that is produced quickly dissipates outwards.

There are three main groups:
1. Standard rod glow plugs
2. Self-regulating rod glow plugs
3. AQGS rod glow plugs.

This glow plug was developed by Niterra to enable automotive manufacturers to comply with ever-stricter emissions standards.
One of the goals of these standards is to reduce the compression ratio in diesel engines. NHTC glow plugs reach a temperature of 1,000°C in less than two seconds. It can after-glow for more than ten minutes at temperatures of up to 1,350°C.

The ceramic high-temperature glow plug (“NHTC glow plug”, “New High Temperature Ceramic”) has a fully ceramic heating element.

The PSG enables real-time combustion monitoring to support optimised engine performance, improved efficiency and compliance with increasingly stringent emissions requirements. The integrated piezo-sensor measures combustion pressure inside the cylinder in real-time and transmits the data to the engine control unit (ECU).

Glow plugs support reliable ignition conditions and efficient combustion in diesel engines. Principally, they are used in ignition, receiving electrical energy and heating up to very high temperatures. They generate the temperature boost that diesel engines need to start, especially in cold conditions.
In normal temperatures, ambient air is drawn into the engine cylinders and then compressed to reach around 900°C. When the fuel is then injected, it ignites spontaneously. However, in winter, conditions for successful ignition become more difficult. The cold cylinder walls, pistons and valves try to extract heat from the cold intake air, and as a result the necessary combustion temperature is not achieved. Extra heat is needed – and that is where the glow plug comes into play. As soon as a current is supplied, the engine’s glow plugs heat up. This provides the extra heat needed for stable combustion. 
Once the engine is running, the glow plugs either return to being idle or continue to work, depending on their type.

The most common symptoms of a bad glow plug are engine misfiring, hard starting, black or white exhaust smoke, decreased fuel efficiency and rough idling.
 

Glow plugs can malfunction for a variety of reasons. These include: excessive heat due to fuel leaking from the injectors, too much voltage caused by a faulty controller or old age.
 

Improving cold starts is just one of the functions of modern glow plugs. They also contribute towards the reduction of engine emissions by generating a ‘post-glow’ for several minutes after ignition, which helps to ensure the diesel fuel completely combusts during the warm-up phase.

Glow plugs also benefit the health of the exhaust gas recirculation (EGR) valve by producing what is known as an ‘intermediate glow’. This helps to prevent the EGR valve from carbonising, which affects its ability to reduce the vehicle’s particle and nitrogen oxide emissions.

In addition, glow plugs support diesel particulate filter (DPF) regeneration (trapped carbon is burned off). To regenerate, the DPF must be heated up to more than 600°C for around ten minutes. One of the measures the ECU performs to achieve this, is the initiation of a ‘regeneration glow’ from the glow plugs. They increase to well over 1,000°C, which raises the combustion chamber temperature. This in turn increases the exhaust gas temperature; supporting DPF regeneration.
 

This depends on a variety of factors. An average estimate is around 160,000km but service life can vary depending on product quality, engine condition, operating conditions and maintenance. NGK glow plugs are designed for long service life and performance.

When a glow plug needs to be replaced, it is recommended to apply a synthetic engine oil around each glow plug and ideally let it penetrate for at least a week. This reduces the risk of shearing and makes removal easier. When removing, each glow plug should be manually disconnected from its electrical wire. When this is complete, each plug can be individually uninstalled with a suitable torque wrench.
 

Once an old glow plug is removed, a glow plug hole reamer loaded with silicone-free grease should be used to clean and empty each hole of carbon deposits. After that, the new glow plugs can be manually installed into their seats and then tightened with a correctly set torque wrench.

Yes. It is recommended to replace all of the engine’s glow plugs at the same time because if one glow plug is faulty, the probability is that the others are not too far behind. The replacement of all the engine’s glow plugs at the same time will reduce maintenance costs in the long term as well as vehicle down-time. It will also help to optimise vehicle performance as the driver can rest assured that all of the engine’s glow plugs are making the same contribution.