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Valve cover gasket replacement

NB-focused cam/valve cover gasket replacement procedure, including gasket quality guidance and common optional while-you're-there checks.

Difficulty
Intermediate
★★☆☆☆
Est. Time
1-2 hours
Models
NB1 & NB2
Last Updated
2026-02-26

Before You Start / Safety

  • Work on a fully cool engine.
  • Disconnect battery negative if you are removing ignition components.
  • Keep debris out of the valvetrain area.
  • Do not overtighten valve cover fasteners; stripped threads and warped covers are common DIY failure points.

Required Tools

  • Metric socket set and ratchet
  • Torque wrench capable of low torque values
  • Plastic scraper / non-marring pick
  • Brake cleaner or degreaser and lint-free rags
  • Small amount of RTV/silicone where the service manual calls for it

Required Parts / Fluids

  • Valve (cam) cover gasket set for your exact NB engine/version
  • Optional spark plug well seals (if included with your gasket kit)
  • Optional PCV valve/hoses if brittle or cracked

Model-specific notes (NB1 vs NB2)

  • NB1 (1998-2000) and NB2 (2001-2005, incl. many VVT 1.8s) share the same maintenance concept but differ in surrounding hardware and exact part numbers.
  • Confirm by VIN/year and engine code before ordering.

Manual-reference quote: BOFI’s workshop-manual index lists NB-specific engine manuals (“99-00 for the bp4w 1.8” and “01-05 for the vvt engine”). (Retrieved 2026-02-26) https://bofiracing.com/blog/mx5-miata-workshop-manuals/

Step-by-Step Procedure

1) Confirm leak source first

Clean the area and verify the leak is from the valve cover perimeter/plug-well area rather than a higher or adjacent source.

2) Remove ignition/obstructing components and valve cover

  • Label anything you disconnect.
  • Remove fasteners evenly.
  • Lift the cover carefully to avoid nicking sealing surfaces.

3) Clean mating surfaces

  • Remove old gasket material gently.
  • Degrease cover channel and head mating surface.
  • Keep debris out of the engine.

4) Install new gasket and seals

  • Seat gasket fully in the valve cover groove.
  • Apply sealant only at the specific corners/joints required by the service procedure.

Community quote: “don’t forget to use high temp silicone for those sharp bends/corners … And use OEM Valve gasket…” (Miata.net NB thread, retrieved 2026-02-26) https://forum.miata.net/vb/showthread.php?t=442560

5) Refit cover and torque in stages

  • Snug all fasteners by hand first.
  • Tighten in small stages and sequence from center-out per manual guidance.
  • Re-check that gasket hasn’t rolled/pinched during seating.

6) Reassemble and verify

  • Refit ignition parts/hoses.
  • Start engine, inspect for leaks at idle and after a full heat cycle.

Torque Specs / Capacities

  • Use your NB workshop manual for exact valve cover fastener torque by engine variant.
  • This guide intentionally avoids publishing an unverified single torque number because accessible public sources in this environment were inconsistent or incomplete.

Verification / Post-service checks

  • No fresh oil around cover perimeter or plug wells after warm-up.
  • No misfire from oil contamination in plug wells.
  • Reinspect after 1-2 drives.

Uncertainty / Open Questions

  • Some detailed step references (e.g., miata.net garage how-to mirror pages) are intermittently blocked by anti-bot protections in this environment.
  • Community advice differs on reusing old gaskets. Conservative approach is to replace with high-quality/OEM-equivalent gasket when opened.

Community quote (reuse caution): “the downside of reusing the gasket is that it leaks and then you’d need to buy a new gasket, and then do the labor again.” (Miata.net NB thread, retrieved 2026-02-26) https://forum.miata.net/vb/showthread.php?t=643394

Images

No reusable images were added in this run. I could not retrieve clearly reusable/licensed NB-specific procedural images from accessible sources.

Image Credits

  • No images used.

Sources

  1. BOFI Racing — MX-5/Miata Workshop Manuals - Including all Torque Settings (NB workshop manual index by year/engine). Retrieved 2026-02-26. https://bofiracing.com/blog/mx5-miata-workshop-manuals/
  2. MiataMechanic — Miata Valve Cover Gasket: NA and NB (1990-2005) (independent how-to overview page). Retrieved 2026-02-26. https://www.miatamechanic.com/2020/07/blog-post_52.html
  3. YouTube (CashedOutCars) — How To Replace a Valve Cover Gasket | Mazda MX5 Miata: 1.6L and 1.8L Engines (NA and NB) (independent how-to video reference). Retrieved 2026-02-26. https://www.youtube.com/watch?v=F_cGcnyb9M4
  4. YouTube (Rick The Spud) — Easily Replace a Valve / Rocker Cover Gasket on a Mazda MX5 Miata NA NB 1.6 1.8 VVT (independent how-to video reference). Retrieved 2026-02-26. https://www.youtube.com/watch?v=DKH9xPP42R4
  5. Miata.net Forum — about to replace valve cover gasket - should I do anything else? (NB forum discussion: PCV checks, gasket quality, corner sealant mention). Retrieved 2026-02-26. https://forum.miata.net/vb/showthread.php?t=442560
  6. Miata.net Forum — Valve Cover Removal/Cleaning - Gasket Replacement Necessary? (NB forum discussion: gasket reuse risk tradeoff). Retrieved 2026-02-26. https://forum.miata.net/vb/showthread.php?t=643394