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NBC2579AA - Spark Seal Plug Boss by Jaguar Land Rover Range Rover

NBC2579AA - Spark Plug Boss Seal – Camshaft Cover

- €11,30
€11,30
€11,30 - €11,30
€11,30
OEM Part
OEM: Made by an Original Equipment Manufacturer. This part is made by an original equipment manufacturer or under their license, ensuring compatibility and quality.
Brand Jaguar
Spark Plug Boss Seal for the camshaft cover of the AJ16 inline-six petrol engine, part of the camshaft cover sealing arrangement.

The seal fits around the spark plug aperture where the camshaft cover meets the cylinder head, closing the plug well off from the cam boxes so that oil circulating over the valvetrain cannot reach the spark plug recess.

The rubber hardens and takes a set with age, allowing oil under pressure to seep into the wells and collect around the plug and ignition coil - a common cause of misfire on this engine, often accompanied by the smell of oil burning off the cover. The seals are renewed together with the camshaft cover gasket and the cover fixing isolators.

Also supplied as a component of the camshaft cover gasket set.
Fitment Notes Spark plug boss seal — camshaft cover.
JAGUAR XJ 1995-1997 (X300) VIN 720125 to 812255 — 3.2L / 4.0L (not 6.0L).
JAGUAR XJS VIN 179737 to 226645 — 4.0L AJ16.
Also serviced as part of a gasket set / cylinder head gasket set.
Not a Land Rover part — Jaguar fitment only.
Alternative Codes
NBC2579AA

Available to order 2–3 weeks

Not currently in stock. Order now — typically ships within 2–3 weeks.

Need it faster? Contact us about express import (2–5 business days).

When will my order arrive?

This item is ordered from our supplier on request. Typical lead time is 2–3 weeks from order confirmation.

  • Netherlands / Belgium / Germany: 2–4 working days after dispatch.
  • Other EU countries + UK: 4–8 working days after dispatch.
  • Outside EU/UK: contact us for an estimate.

Need it faster? Express import available in 2–5 business days — contact us before ordering.

Job kits containing this part

This part is included in 0 job kit(s) below. Pick the kit that matches your vehicle and job, then add what you need.

Frequently asked questions

What is the spark plug boss seal (NBC2579AA) and what does it do on the AJ16?
The spark plug boss seal sits at the camshaft cover where each plug well passes through it, sealing the well from the oil-wetted valvetrain cavity above. When it hardens and fails, engine oil pools around the spark plug and coil, a common cause of misfire and oil smell on AJ16-powered Jaguars.
Why does the spark plug boss seal need replacing, and what symptoms suggest it has failed?
The seal hardens with heat cycling and loses its ability to hold oil back from the plug wells. Signs include misfire under load, oil-fouled spark plugs, and a burning oil smell from the camshaft cover area.
Does this seal fit all AJ16-powered Jaguar models?
It fits the Jaguar XJ (X300) from VIN 720125 to 812255 in 3.2L and 4.0L form (not 6.0L), and the Jaguar XJS from VIN 179737 to 226645 in 4.0L AJ16 form. This is a Jaguar-only part and does not fit any Land Rover model.