F00041N055 Injector Seal Kit – Sealing System Harmonisation For CRI 2.4 High‑Flow Applications

 

The F00041N055 service kit addresses a fundamental challenge in injector remanufacturing: the degradation of sealing components alters the hydraulic balance within the injector, shifting the relationship between control chamber pressure and needle lift. This kit is specifically engineered for a family of Bosch CRI 2.4 injectors that feature a larger flow coefficient and faster pressure build‑up characteristics compared to earlier generations. Rather than supplying generic seals, the F00041N055 provides a matched set of components that restore the original clearances and compression forces across the injector's three sealing zones-the high‑pressure inlet, the control piston dynamic seal, and the low‑pressure return circuit. The kit's design prioritises maintaining the injector's hydraulic capacitance, a parameter that influences the rate of pressure decay during injection and directly affects the steepness of the needle lift curve. This focus on system‑level behaviour distinguishes the F00041N055 from conventional repair kits that merely replace parts without considering their collective impact on injection dynamics.

 

The F00041N055 is dimensionally matched to the following injector part numbers, all of which share identical sealing groove profiles, filter housing dimensions, and inlet seat geometry:

0414703009

These injectors are found in commercial vehicle applications including DAF XF, Iveco Stralis, and certain Volvo FH variants, operating with rail pressures up to 1,800 bar. The kit's primary O‑ring features a 2.2 mm cross‑section diameter-specific to the CRI 2.4 platform-and the return seal measures 1.8 mm. The copper washer is dimensioned with an outer diameter of 15.0 mm, an inner diameter of 9.0 mm, and a thickness of 1.6 mm. The backup ring has a thickness of 0.9 mm, calibrated for the groove width range found in these injector bodies. A notable addition is the inclusion of a secondary PTFE guide ring, which centres the control piston during assembly, preventing off‑axis loading that can damage the O‑ring during installation.

 

The F00041N055's component materials are selected to maintain the injector's hydraulic capacitance-the volume of fuel compressed under pressure-which influences the amount of fuel delivered during the initial opening phase. The O‑rings are produced from a hydrogenated nitrile butadiene rubber (HNBR) compound with a hardness of 82 Shore A, chosen for its low compression set (under 8 % at 150°C) and its superior resistance to fuel degradation compared to standard FKM in high‑temperature applications. The backup rings are moulded from a polyetheretherketone (PEEK) composite with 30 % carbon fibre reinforcement, providing a compressive modulus of 8.5 GPa-sufficient to resist extrusion at 2,000 bar while maintaining dimensional stability. The copper washer is annealed to HV 80‑85 and coated with a thin layer of tin to prevent galvanic corrosion between the steel nut and the aluminium injector body. This coating also provides a consistent friction coefficient, ensuring that the torque‑angle relationship remains predictable across repeated installations.

 

The inlet filter supplied in the F00041N055 is constructed from a twill‑weave stainless steel mesh with an absolute filtration rating of 25 microns, but its effective open area is increased by 30 % compared to standard filters through the use of a wavy profile that creates additional surface area. This design ensures that the pressure drop across the filter remains below 0.12 bar at flow rates up to 2.2 L/min, which is the maximum fuel consumption of these injectors at full load. The filter frame incorporates a spring‑loaded retention clip that holds the mesh securely in place, preventing it from shifting or collapsing under reverse pressure pulses. The kit includes a removal tool with a threaded tip that screws into the filter's centre, allowing extraction without contacting the bore wall-a critical safeguard for injector bodies that have been previously reworked and may have a polished bore surface.

 

The installation of the F00041N055 requires a specific sequence that accounts for the interaction between components. The copper washer must be installed first and torqued to 35 N·m without the O‑ring in place, because the compression of the washer slightly deforms the inlet seat, which can shift the O‑ring groove position. After the washer crush is completed, the O‑ring and backup ring are installed together, with the backup ring positioned on the high‑pressure side of the O‑ring (closest to the combustion chamber). The inlet nut is then re‑tightened to 38 N·m plus a 70° angular advance, which is calculated to produce a specific washer height reduction of 0.32‑0.36 mm. The return fitting uses a separate torque of 28 N·m, applied after the main seal is fully set. The kit also includes a set of coloured identification rings (blue, green, red) that can be placed over the injector body to indicate the service date, a practical traceability feature for fleet workshops managing multiple overhauls.

 

Q1: The F00041N055 O‑rings have a different colour than the originals. Does the colour indicate a different compound?
A: Yes, the colour coding identifies the HNBR material used in this kit, which has a higher heat resistance than the original FKM. The orange colour is a manufacturing marker and does not affect performance, but it helps workshops quickly identify that the correct material has been installed.

Q2: Can the PEEK backup ring be reused if the injector is disassembled for inspection after a short run?
A: No. The PEEK ring experiences micro‑creep during the initial compression and its anti‑extrusion geometry becomes work‑hardened. Reusing it can lead to premature leakage. The F00041N055 backup rings should be treated as single‑use components, even if they appear undamaged.

Q3: How does the tin coating on the copper washer affect the torque specification?
A: The tin coating reduces the coefficient of friction between the washer and the steel nut, which means that a lower torque is needed to achieve the same crush compared to an uncoated washer. The kit's specified 35 N·m + 70° accounts for this; do not use torque values intended for uncoated washers.

Q4: I have an injector that was previously modified with a larger control piston. Will this kit fit?
A: No. The F00041N055 is designed for standard CRI 2.4 dimensions. A larger control piston changes the groove depth and diameter, requiring custom‑sized seals. This kit is not suitable for modified injectors.

Q5: The filter mesh is very fine. What happens if fuel quality is poor and it blocks prematurely?
A: The filter is designed to trap debris without blocking, but if fuel with excessive contamination is used, the mesh may become plugged. The kit includes an additional filter mesh as a spare, which can be replaced during the next service interval without replacing the entire kit.

Q6: After installation, the injector shows a slightly higher return flow at idle. Is this acceptable?
A: A slight increase (up to 2 ml/min) is acceptable as the new O‑ring settles into the groove. However, if the return flow exceeds 18 ml/min, it indicates that the backup ring is not properly seated or that the O‑ring has been pinched. Re‑inspect the installation and verify that the backup ring is correctly oriented.

 

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