Under-tightening can cause overheating due to poor heat dissipation and in extreme cases can cause spark plug breakage and/or major engine damage.Ħ. Over tightening can lead to distortion of the spark plug and breakage. This will render the torque readings inaccurate and over tightening could occur by up to 20 percent! It’s very important not to over or under tighten spark plugs during installation. NGK does not recommend the application of lubricant such as copper grease to spark plug threads as the result is a reduction of frictional forces at the thread faces. Make sure your torque wrench has the correct load ranges and that it has a calibration certificate, spark plug torque settings are reasonably low so a smaller wrench will be necessary. If you have a torque wrench, tighten to the specified torque setting in the table below. Install new spark plugs and finger tighten them until they stop – A length of rubber tubing pushed over the insulator a useful aid for plug installation where access is difficultħ. Warning – Do NOT apply copper grease/slip or anti-seize to the plug threads, copper grease is only for used on old fashioned black spark plugs which have no corrosion resistant zinc plating.Ħ. Multi-ground electrode and precious metal plugs (iridium, platinum tip etc) should not be re-gapped due to risk of damaging the fine tips.ĥ. Ensure the plug is gapped according to the vehicle manufacturers specification. After removing the old spark plugs, check the condition and cleanliness of the cylinder head threads, if they’re dirty then this can lead to inaccurate torque wrench readings, it is paramount however that care must be taken so no dirt falls into the cylinders, some kitchen roll and a little carb cleaner sprayed onto it should do the trick.Ĥ. Try not to use penetrating lubricant as once the plugs are removed any dirt and fluid can run into the cylinders.ģ. If they feel seized it’s advised to use an impact wrench at a low torque setting to ‘shock’ the plugs free. Blow away any debris from the plugs recess area and carefully undo the old spark plugs with the correct sized socket that is specially made for spark plugs, they are usually much longer than standard sockets. Locate the spark plug covers and remove them by pulling them upwards.Ģ. NGK released an official tech bulletin to all suppliers about the issue with copper slip.ġ. The NGK warranty reports are always compiled of detailed photographs pinpointing the reasons of exact failure, even to the very smallest of details such as hex swelling is recorded. As of now, it turns out 100% of the spark plugs in the last 3 years that were returned due to breakage were the result of customers using thread compound and simply over tightening with a torque-wrench. This goes for anything and everything to do with torque-wrenches, always use torque specifications ‘dry’ unless stated otherwise.įor NGK warranty purposes we must send all damaged plugs back to them to be officially examined and documented. You will end up over-tightening them by up to 20% which is easily enough to break them if using an anti seizure agent. The preload is the ‘tension’ between the plug and cylinder head threads that gives the friction force to stop them coming loose. The reason is because there’s less friction between the two materials and far more force can be applied into the plugs preload when using thread compound or copper grease. Why Do Torque Values Change With Copper Slip?
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