One of the OE parts supplied by Denso are glow plugs, so the firm is in an ideal position to dispel an ongoing myth surrounding the part…
Alongside many other products, Denso is a glow plug manufacturer, supplying them as original equipment parts. It also supplies the independent service and repair sector and as its aftermarket range is produced on the same production lines to the same standards, the firm argues they can be relied on by automotive technicians and motorists alike. There is, nevertheless, a notion among workshops that the colour of a glow plugs’ tip can imply that it is not a genuinely new item.
According to the company, the fact that its aftermarket glow plugs are manufactured on the same production line as its OE range, should be enough to reassure those with any concerns over the providence of its glow plugs. However, to clarify the situation and provide peace of mind for installers, Denso is explaining why the tips have this colouration.
In common with many highly engineered products, the manufacture of glow plugs is a complex process. This is particularly true for the production of the glow tube, which when installed, can be heated up to temperatures above 800°C within seconds. This component is needed to ensure a quick and reliable start when the engine is cold, and to reduce emissions when it is running.
Live testing
As this heating element is the most critical component of the glow plug and allows it to fulfil its role in the ignition system, its functionality has to be verified during the production process. It is for this reason, that at the end of the production line, the performance of each glow plug is thoroughly tested to ensure that it is working in accordance with the given specification, including its heat-up time and the temperature it needs to reach.
It is this in-line production test, that causes the glow plug’s tip to take on this grey/blue tone. This colouration is due to the oxidation of the metal, which is accelerated by the high temperature it is subject to during the test, but it does no harm to the glow plug, nor does it degrade its performance.
Therefore, rather than being something of concern to technicians when opening the box, it should be regarded as a sign of reassurance, because it indicates that the glow plug they are about to fit has been tested and works according to its given specification, and will perform as they’d expect a large OE automotive parts supplier.
Denso’s R&D investment helps it to pioneer increasingly efficient and reliable diesel engines with minimal emissions. Its aftermarket division draws on this expertise, offering a comprehensive, all-makes glow plug programme intended to improve start-up performance with extended post-heating temperatures.
