Genuine Mazda Cylinder Head Bolt Plain Washer • ZJ01-10-138

Genuine Mazda Cylinder Head Bolt Plain Washer

Replacement Genuine Mazda cylinder-head bolt washer for Mazda MX-5 Mk1 NA, Mk2 NB and Mk2.5 NB-FL models fitted with 1.6- or 1.8-litre petrol engines.

The plain washer fits beneath the head of a cylinder-head retaining bolt. It provides the correct seating surface between the bolt and cylinder head, helping distribute the clamping load applied when the cylinder-head fasteners are tightened.

Correct cylinder-head clamping is essential for maintaining an even seal between the cylinder head, head gasket and engine block. A damaged, distorted or missing washer can affect fastener seating and the accuracy of the tightening procedure.

Ten washers are fitted per engine, while this listing supplies one Genuine Mazda washer. Order a quantity of ten when replacing the complete engine set.

Engine coverage: This washer is used with the cylinder-head bolts on 1.6- and 1.8-litre Mazda MX-5 NA and NB-family engines, including later Mk2.5 1.8 VVT applications.

• Part type: Cylinder-head bolt plain washer
• Common names: Head-bolt washer / cylinder-head fastener washer
• Mazda catalogue description: Washer, Plain Cylinder Head
• Installation position: Beneath the cylinder-head bolt head
• Function: Provides the correct bolt seating surface and distributes clamping load
• Engine applications: 1.6- and 1.8-litre petrol engines
• Quantity fitted per engine: 10
• Quantity supplied: 1 washer
• Cylinder-head bolt included: No
• Cylinder-head gasket included: No
• Other washers included: No
• Brand: Genuine Mazda
• Part No.: ZJ01-10-138
• Earlier Mazda references: B630-10-138 and B630-10-138A
• MX-5 fitment: Mk1 NA, Mk2 NB and Mk2.5 NB-FL 1.6 and 1.8 models

Typical reasons for replacement:

• Washer missing during cylinder-head reassembly
• Original washer visibly distorted or dished
• Seating face scored, burred or damaged
• Corrosion affecting the washer surface
• Washer damaged during engine dismantling
• Cylinder-head bolts and related hardware being renewed
• Engine being rebuilt or cylinder head being replaced
• Incorrect non-standard washer previously installed

Quantity advice: Ten washers are required for a complete MX-5 engine. This listing supplies one washer per order quantity.

Fitment advice: This component is the washer installed beneath the cylinder-head bolt. It should not be confused with camshaft-cover sealing washers or other engine fastener washers.

Inspection advice: Inspect every cylinder-head bolt and washer during dismantling. Replace washers that are distorted, cracked, heavily corroded or damaged around the seating face.

Fastener advice: Follow the applicable Mazda workshop procedure for cylinder-head bolt inspection, reuse or replacement. The bolts must be installed in the specified sequence and tightened through the required stages.

Installation advice: Ensure that the washer and the corresponding seating surface on the cylinder head are clean and free from burrs, old sealant and debris. The washer must sit flat before tightening begins.

Engine-work advice: When the cylinder head has been removed, inspect the head and block surfaces for distortion, corrosion and damage. Replace the head gasket and any other single-use components required by the Mazda procedure.

Other items to consider: Inspect the cylinder-head bolts, cylinder-head gasket, locating dowels, camshaft-cover gasket, inlet-manifold gasket and exhaust-manifold gasket while the engine is dismantled.

Useful tools / consumables: Correct socket, calibrated torque wrench, angle gauge where required, thread-cleaning equipment, straight edge, feeler gauges and suitable parts cleaner.

Difficulty guide: DIY Difficulty: Advanced when installed as part of cylinder-head removal or engine rebuilding. Accurate inspection and strict adherence to the Mazda tightening sequence are essential.

Why Genuine Mazda? Genuine Mazda cylinder-head bolt washers match the original diameter, thickness and seating profile specified for the Mazda fastener arrangement. Correct hardware helps the head bolts apply an even and repeatable clamping load.

What’s in the box: One Genuine Mazda cylinder-head bolt plain washer, part number ZJ01-10-138.

Installation notes: Clean the cylinder-head bolt, washer and seating surface before assembly. Position one washer beneath each cylinder-head bolt and confirm that every washer sits flat. Install and tighten the bolts only in the sequence and stages specified by the applicable Mazda workshop procedure. Do not substitute general-purpose washers of unknown dimensions or material specification.