Difficulty
Moderate
Steps
10
Time Required
01:00:00
- Replacing the glow plugs 10 steps
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User contributed
Introduction
On these recent direct injection engines, the glow plugs are not used much, except in the case of low outside temperatures (0°C and below). However, they participate in a post-heating operation which reduces pollutant emissions during the first minutes of operation. Consequently, they can only cause starting difficulties in very cold weather, and their service life is increased.
Replacing the glow plugs, although simple on paper, is a delicate operation. Indeed, carbon and oxidation can block the spark plug pencil in the cylinder head duct, which can lead to spark plug breakage. A long and tedious disassembly of the cylinder head would be expected in this case.
Given this risk, NISSAN only recommends action on these spark plugs if necessary.
To facilitate disassembly, this will be done with the engine hot. Conversely, to prevent the cylinder head from squeezing the spark plug as it cools, the spark plugs will be reassembled with the engine cold.
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The glow plugs are located on the left side of the engine, so on the right when working facing the hood.
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Removing the plastic engine cover may make access easier, or at least visibility. To remove it, remove the 2 screws then lift the cover upwards, taking care not to disconnect the vacuum pipes under the windshield bay when handling it.
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Remove the black plastic terminal covers from the threads at the electrical connection of the spark plugs. These are removed by unscrewing.
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Unscrew the spark plug terminal nuts.
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Remove the spark plug power connector, being careful not to lose the washer under the nut during removal.
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Remove the power strip.
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Blow compressed air around the spark plug wells to remove large impurities before removal.
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As stated in the introduction, spark plugs can break in the cylinder head during disassembly if they are seized. The breaking torque of the spark plugs is around 35 Nm. It is advisable to remove the spark plugs with a torque wrench (which can operate in the loosening direction).
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It is also possible to limit yourself to using a 1/4 size ratchet used with one hand to be certain not to exceed the breaking torque.
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Given the geometry of the spark plug, the use of a 12mm long socket is recommended. A 250mm extension makes access easier.
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Remove the 4 spark plugs. As stated in the introduction, it is recommended to perform this operation when the engine is hot.
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Using a long-nose blow gun, blow compressed air into the spark plug wells to remove carbon debris.
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The carbon is friable, it is not harmful to the engine and will be expelled through the exhaust.
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The compressed air pressure is sufficient to drive the engine through half a crankshaft revolution. Check that the area around the engine fan is clear to allow it to rotate freely.
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Complete cleaning of the duct is carried out with a specific reamer. Coat it with grease to limit the fall of carbon debris into the combustion chamber.
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Insert the reamer into the conduit and clean.
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The shape of the cylinder head around the wells does not allow the use of the reamer centering devices provided in standard cleaning kits. Therefore, use the tool gently so as not to attack the sealing cone in the well.
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Blow through the duct again to clear out any remaining grease and debris.
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With extreme care, unpack the new spark plugs. For information, NISSAN recommends the systematic disposal of any spark plug that falls more than 10 cm. Indeed, a spark plug weakened by an impact could break in the engine the next time it is disassembled, or even during operation given the heating cycles.
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The photo shows the two main types of spark plugs available: ceramic spark plugs fitted as standard and classic replacement spark plugs.
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To make the next disassembly easier, apply a high temperature (copper) grease to the spark plug threads.
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Carefully insert the spark plugs into their wells, then screw them in until they are firmly seated. If the thread is clean, screwing them in by hand should not present any hard spots.
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NISSAN recommends tightening spark plugs to 20.8 Nm. Manufacturers of replacement spark plugs recommend torques between 15 and 20 Nm.
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Given the application of grease on the threads, the compression force of the spark plug on the cylinder head is greater than dry for the same tightening torque. A torque of 10 Nm is therefore sufficient to guarantee sealing at the cone.
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Tighten the spark plugs using the torque wrench. It is recommended to perform this operation when the engine is cold.
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Proceed to reassemble the electrical connection in the reverse order of disassembly.
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