Genuine Mazda PCV Valve / Cam Cover Breather Valve – MX-5 Mk2 1.8 • B541-13-890A

Genuine Mazda B541-13-890A PCV Valve / Cam Cover Breather Valve

Replacement Genuine Mazda positive crankcase ventilation valve for Mazda MX-5 Mk2 NB 1.8-litre models produced from 1998 to 2000.

The PCV valve forms part of the engine’s crankcase-ventilation and emissions-control system. It regulates the flow of blow-by gases and oil vapour from the crankcase into the intake system, where they are burned during normal combustion.

On the applicable MX-5 Mk2 NB 1.8 engine, this is the distinctive 90-degree elbow-style valve fitted in the breather hose running between the rocker cover and intake manifold chamber.

During normal engine operation, a small quantity of combustion gas passes the piston rings and enters the crankcase. The PCV system allows these gases to leave in a controlled manner while helping maintain suitable crankcase pressure.

A blocked or restricted valve can allow crankcase pressure to increase, potentially contributing to oil leakage, increased oil consumption and contamination within the breather system. A valve stuck open may create an unintended intake-air path and contribute to unstable idle, poor running, hissing noises or mixture-related faults.

• Part type: Positive crankcase ventilation valve
• Common names: PCV valve / cam-cover breather valve / crankcase breather valve
• Mazda catalogue description: Valve, P.C.V.
• Valve configuration: 90-degree elbow type
• Primary use: Regulates crankcase-vapour flow into the intake system
• Location: Breather hose between the rocker cover and intake manifold chamber
• Quantity fitted per engine: 1
• Quantity supplied: 1 PCV valve
• Brand: Genuine Mazda
• Part No.: B541-13-890A
• Also referenced as: B54113890A
• Replaces: B541-13-890 / B54113890
• MX-5 fitment: Mk2 NB 1.8 models from 1998 to 2000 only

Important: This is not the general straight-style PCV valve used on MX-5 Mk1 models, Mk2 1.6 models or Mk2.5 vehicles. It is the 90-degree elbow version specifically used on the early Mk2 NB 1.8 application.

Possible signs of a PCV-system problem:

• Increased crankcase pressure
• Oil seepage from engine seals or gaskets
• Increased oil consumption
• Rough or unstable idle
• Whistling or hissing from the breather system
• Oil contamination inside the intake system
• Split, collapsed or oil-softened breather hoses

Fitment advice: This valve is specifically confirmed for Mazda MX-5 Mk2 NB 1.8-litre models from 1998 to 2000. Check that the original installation uses the same 90-degree elbow valve and hose arrangement before ordering, particularly on vehicles with a replacement engine or cam cover.

Other items to consider: Inspect the associated rocker-cover breather hose, intake-manifold connection, hose clips and surrounding vacuum hoses. Brittle, split, blocked, collapsed or oil-softened hoses should be replaced where necessary.

Useful tools / consumables: Hose-clamp pliers, suitable general-purpose pliers, small trim tool, lint-free cloths and intake-safe cleaner. Replacement hose clips or breather hose may be required if the originals have deteriorated.

Difficulty guide: DIY Difficulty: Easy. The valve is normally accessible from the upper engine bay. Care should be taken when disconnecting aged breather hoses because heat and oil exposure can make the rubber brittle.

Why Genuine Mazda? Genuine Mazda PCV valves are designed to provide the original flow-control characteristics, connection dimensions and internal valve operation required by the engine’s crankcase-ventilation system. Correct operation helps maintain controlled crankcase pressure and consistent engine running.

What’s in the box: One Genuine Mazda PCV valve / cam-cover breather valve, part number B541-13-890A.

Installation notes: Allow the engine to cool before removing the breather hose. Clean the surrounding area, release the hose clips and remove the old valve carefully. Inspect the hose internally for sludge or restriction and check the rubber for cracking or softening. Install the replacement valve in the same flow direction and orientation as the original, secure the hose connections and check for vacuum leaks and correct idle operation.