Spark Plug specialist NGK has issued advice on plug replacement on BMW N43 and N53 engines, which were fitted with ZKBR7A-HTU NGK spark plugs as original equipment.
The engines feature on the BMW 1 series and under the bonnet of a 3, 5 or 6 model. The spark plug is a semi-surface type, with three ground electrodes and a 14mm bi-hex.
When it comes to replacement, correct tool selection is essential. The NGK replacement plug (stock no. 91785), is identical to the OE and replaces BMW part nos.12120038349 and 755001102.
Unlike most engines, the spark plugs position in the N43 and N53 is angled in the spark plug tunnel by more than five degrees. A look into the spark plug shaft does not reveal this special design to technicians and, unaware of this particular construction, the mechanic might mistakenly use a standard solid bi-hex (12 point) socket, instead of the necessary bi-hex socket with an integral articulated joint. Due to the angled position, a conventional solid spark plug socket will not fit squarely on the spark plug. The force required to loosen or tighten the plug means that the risk of spark plug damage is high. Sometimes cracking cannot be seen, as they are out of sight beneath the metal shell of the spark plug. Ignition problems and an early failure of the spark plug are inevitable, resulting in costly diagnostic time.
When replacing spark plugs on the N43 and N53 engines, NGK say technicians need to be sure to use a quality articulated bi-hex socket, available from specialist tool manufacturers. It should be used in conjunction with a torque wrench upon installation (set to 15 – 20 Nm for this 12mm diameter thread plug).