A Guide to the Engine Valve Cover Gasket for the 1990-2000 Mazda Miata
Stop that burning oil smell and keep your Miata's engine clean and leak-free.
- A burning oil smell is the most common sign of a failed valve cover gasket on a Miata.
- Always replace the Cam Angle Sensor (CAS) O-ring at the same time, as it's another common leak point often misdiagnosed as the valve cover gasket.
- Use a torque wrench. Over-tightening the bolts is a common mistake that will cause the new gasket to leak.
- Make sure to order the correct gasket for your engine, as the 1.6L (1990-93) and 1.8L (1994-00) gaskets are different.
Is your Miata's valve cover gasket failing?
The valve cover gasket on the 1.6L and 1.8L Miata engines lives in a hot environment. Over time, the rubber becomes hard, brittle, and shrinks. This prevents it from sealing properly, leading to common and obvious symptoms.
Symptoms of a Leaking Valve Cover Gasket:
- Oil on the Engine: You will see fresh oil or caked-on dirt and grime on the side of the engine, just below the valve cover.
- Burning Oil Smell: This is the most common complaint. As oil leaks from the gasket, it drips onto the hot exhaust manifold, creating a noticeable burning smell in and around the car.
- Oil in Spark Plug Wells: If the spark plug tube seals fail, oil can leak into the spark plug tubes. This can lead to a misfiring engine and damage to the spark plug wires.
- Low Engine Oil: A significant leak can lead to a noticeable drop in your engine oil level over time.
Check the CAS O-Ring First!
A very common oil leak on 1990-2000 Miatas comes from the Cam Angle Sensor (CAS) O-ring. This sensor is located at the back of the valve cover (intake side on 1.6L, exhaust side on 1.8L). Its O-ring is notorious for failing and dripping oil down the back of the engine, which is often mistaken for a valve cover gasket or rear main seal leak. It is highly recommended to replace the CAS O-ring whenever you replace the valve cover gasket.
🎬 See how to replace the CAS O-ring and gasket together.Choosing the Right Aftermarket Gasket
While a genuine Mazda gasket is always a safe bet, several aftermarket brands offer good quality and value. The key to a successful replacement is proper installation, but starting with a quality part is essential.
Brand Quality Tiers
- Premium Aftermarket (OEM-Equivalent): Brands like Beck Arnley and Victor Reinz have a strong reputation in the Miata community. Beck Arnley often repackages original equipment parts, and Victor Reinz is known for its OE-quality gaskets. These are reliable choices for a long-lasting seal.
- Standard Aftermarket: Brands like Apex fall into this category. While functional, there is less community feedback on their long-term reliability compared to premium brands or OEM. Some Miata owners have reported mixed results with other standard brands like Fel-Pro, citing issues with fit and material that can lead to premature leaks.
Installation is Key
Even the best gasket will leak if installed incorrectly. The most critical steps are:
- Thoroughly cleaning the valve cover and cylinder head surfaces. 🎬 Watch a walkthrough on deep cleaning and painting your valve cover.
- Applying a small dab of RTV sealant at the sharp corners where the front cam caps meet the head.
- Following the correct bolt-tightening sequence, starting from the center and working your way out.
- Using a torque wrench to tighten the bolts to the very low factory spec of 43-78 inch-pounds (about 4-6.5 ft-lbs). Over-tightening will damage the gasket and cause leaks.
Cost of Replacing a Miata Valve Cover Gasket
| Part Type | Price Range |
|---|---|
| New Aftermarket Gasket Set | $19.05 - $56.32 |
| New OEM Mazda Gasket Set | $35 - $60 |
| Shop Labor | $100 - $180 |
Frequently Asked Questions
Is there a difference between the 1.6L and 1.8L gaskets?
Yes, the gaskets are different and cannot be used interchangeably. The 1990-1993 Miata uses a 1.6L engine, and the 1994-2000 Miata uses a 1.8L engine. An easy way to tell is that 1.6L valve covers have raised lettering, while 1.8L covers have recessed lettering. Be sure to order the correct gasket for your engine.
🎬 Watch this step-by-step guide for replacing the 1.6L gasket.Do I really need to use RTV sealant?
Yes. A small amount of oil-resistant RTV sealant is required in the sharp corners at the front of the engine, where the cam caps meet the cylinder head. This is a factory procedure. Applying it helps prevent leaks from these critical points. Do not apply sealant around the entire gasket.
Can I do this job myself?
Absolutely. Replacing the valve cover gasket is a classic DIY job for Miata owners and a great way to get familiar with your engine. It requires basic hand tools and should take about one to two hours. There are many video guides available that walk through the entire process.
Are there any recalls for this part?
No, there have been no recalls or technical service bulletins (TSBs) issued by Mazda or the NHTSA for the valve cover gasket on 1990-2000 Miatas. Failures are due to the age and normal wear of the part.
Helpful Videos
Technical Specifications
OEM Part Numbers: B61P-10-235B (1.6L Engine) BP05-10-235C (1.8L Engine)
Torque Specification: 43-78 in-lbs (inch-pounds), NOT ft-lbs.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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