Smart Car Spark Plug Replacement: A Step-by-Step Guide with the Essential Lead Removal Tool

Your smart car’s spark plugs are vital components, igniting the air-fuel mixture in the engine. Located in a high-action area, they can fire up to 3,000 times per minute. Like any wear item, spark plugs need replacing, typically as part of regular maintenance. This guide will walk you through replacing the spark plugs in your smart car, emphasizing the importance of using a Smart Car Spark Plug Lead Removal Tool to prevent damage.

Choosing the Right Spark Plugs

Before you begin, you’ll need the correct spark plugs for your smart car. The type varies depending on your engine model. Purchase a set of six new spark plugs.

599cc Engine

6 x NGK BKR6EKE

698cc Engine

6 x NGK R LKR8A
6 x NGK R LKR8AP

Essential Tool: HT Lead Removal Tool

A smart car spark plug lead removal tool is crucial for this job. Do not attempt to remove the HT leads by pulling the wires directly. This can cause significant damage to the leads, necessitating replacement. Investing in or borrowing the correct tool will save you time and money in the long run.

Preparing for Spark Plug Removal

Access the Engine: Begin by removing the rear panels of your smart car. If you need guidance, instructions for the 450 model can be found here on the original website.
Improve Accessibility (Optional): For easier access, especially when working with certain smart car spark plug lead removal tools and socket extensions, you can remove the rear crash bar. This involves unscrewing three Torx45 bolts on each end (six total). While not mandatory, removing the crash bar can provide valuable extra space.

Removing the Bottom Spark Plugs

Locate Bottom Plugs: With the rear panels removed, you’ll see the three lower spark plug leads.
Use the Spark Plug Lead Removal Tool: The spark plug caps can be very difficult to detach. This is where a smart car spark plug lead removal tool becomes indispensable. Avoid using pliers or pulling on the wires, as this can damage the leads.
- Tool Options: While you can find generic HT lead removal tools online (e.g., eBay) or at auto parts stores, some tools are better than others. Smart even offers their own tool (part number A 638 581 02 67), but it’s known to be less effective and can potentially slip and damage the leads. For a superior option, consider brands like Hazet (models 1849-9 or 1849-6). You can also fashion a DIY tool from 20mm tubing if you are experienced.
Engage and Remove the Caps: Slide the smart car spark plug lead removal tool down the spark plug lead. Rotate the tool until its lugs are securely positioned under the “ears” of the cap (as indicated in the image below). Gently pull upwards until the cap detaches from the spark plug. Be patient and avoid excessive force, as the caps can be very tight.
Alternative Method: Some mechanics use long-nosed pliers to grip the caps in the same area where the removal tool engages, but this method carries a higher risk of damage if not performed carefully.
Expose the Spark Plugs: After removing all three lower plug leads, carefully position them away from the work area, such as on the turbo heat shield. The three lower spark plugs are now accessible.
Remove the Spark Plugs: Use a 16mm deep socket and extensions to reach the spark plugs. A specialized 10mm spark plug socket can also be used. Unscrew and remove the old spark plugs.

Installing the Bottom Spark Plugs

Apply Copper Grease (Optional): A small amount of copper grease on the spark plug threads is a debated topic. While it may prevent seizing in the future, ensure you adjust torque accordingly if used (more on this later).
Install New Spark Plugs: Carefully thread the new lower spark plugs into their positions by hand to avoid cross-threading.
Torque Settings: Tighten the spark plugs to the correct torque specifications:
- 599cc Engine, NGK BKR6EKE:
  - New: 27.5 Nm
  - Used: 20.0 Nm
- 698cc Engine, NGK R LKR8A/LKR8AP:
  - New & Used: 22.5 Nm
Do not overtighten the spark plugs.
Reattach Plug Caps: Slide the plug caps back onto the new spark plugs. You might need a gentle tap to fully seat them. A long screwdriver placed on the plug lead ears and a light tap with your palm can help.
Reassemble: Ensure everything is secure, plug leads are firmly attached, and if removed, reinstall the rear crash bar.

Removing the Top Spark Plugs

Access Top Plugs: Access the top three spark plugs from the “boot” area. Remove the engine cover.
Remove Top Plug Leads: Use your smart car spark plug lead removal tool to detach the three top plug leads, similar to the bottom plugs. Note that these leads are also clipped in place on top of the engine.
Clean Debris: Before fully removing the top spark plugs, loosen them a couple of turns. Use compressed air or a straw to blow away any debris around the threads to prevent it from falling into the engine cylinder.

Installing the Top Spark Plugs

Apply Copper Grease (Optional): As with the bottom plugs, consider a small amount of copper grease.
Install and Torque: Install the new top spark plugs and torque them to the same specifications as the bottom plugs (refer to torque settings above based on your engine type). Do not overtighten.
Reattach Caps and Secure Leads: Reattach the plug caps, ensuring they are fully seated with a gentle tap if needed. Press the leads back into their securing slots on the engine.
Replace Engine Cover: Reinstall the engine cover in the boot.

Spark Plug Gaps

NGK spark plugs designed for smart cars typically come pre-gapped. However, it’s always good practice to double-check the gap:

Plug: BKR6EKE (599cc engine only)
Gap: 0.65 mm +/- 0.05mm

Copper Grease: To Use or Not to Use?

The use of copper grease on spark plug threads is a long-standing debate. While some argue it prevents seizing, others believe it can lead to over-torquing due to reduced friction.

Pro-Copper Grease Argument: Prevents seizing, especially in dissimilar metals. However, if using grease, torque values might need slight adjustment downwards.
Anti-Copper Grease Argument: Modern spark plug coatings are designed to prevent seizing. Correct torque without grease is sufficient and recommended by some manufacturers.

Alternative Method (with Copper Grease): Finger-tighten the spark plug as much as possible, then use a ratchet to turn it an additional half turn. This method relies on squashing the fire seal ring and is sometimes manufacturer-recommended as an alternative to torque settings when using lubricated threads.

Ultimately, the choice is yours. Whether you choose to use copper grease and adjust torque or follow the specified torque settings on clean threads, the most important thing is to avoid overtightening and to use a smart car spark plug lead removal tool to protect your HT leads during the process.