Clutch Master Cylinder 8-97048567-0 / 8970485670 For ISUZU NKR55 NPR 4JB1 4BD1 — 3/4" (19.05 Mm) Bore, ISO/TS16949, MAMUR/IZUMI Quality

The Clutch Master Cylinder Assembly with OEM references 8-97048567-0 / 8970485670 is a verified replacement hydraulic pressure generator for ISUZU NKR55, NPR58, NPR59, and NPR66 light trucks, covering the 1984–1998 production span. This cylinder is the hydraulic source at the top of the clutch actuation system — it converts clutch pedal force into hydraulic pressure that travels through the clutch line to the slave cylinder, disengaging the clutch for gear changes.

The unit is defined by its 3/4-inch (19.05 mm) piston bore, a specification confirmed across multiple independent technical sources including Dorman, Brettstruck, and Thai brake suppliers. It is widely cross-referenced under the MAMUR (M-3817) and IZUMI brands, with ISO/TS16949 certification, and is also cross-compatible with JAC 6700 / JMC 1030 / 1040 applications via the JAC OEM reference 1602100Z2-1107. Reference net weight is 0.8 kg.

The 19.05 mm bore is the defining hydraulic specification for this master cylinder. A different bore size will alter pedal effort and clutch release travel. Confirm the original unit's bore diameter before ordering.

This cylinder is confirmed for the NKR55 (2.8L, 1985–1998) and NPR58/NPR59 applications, as well as the NHR55 (2.8L, 1988–1998). It is not a universal ISUZU clutch master cylinder — other N-Series variants (e.g., NKR66 4HF1, NPR66 4HF1) use different references. Confirm the vehicle's chassis code and VIN.

The same master cylinder serves ISUZU NKR/NPR, JAC 6700, and JMC 1030/1040 applications. This is a cross-brand SKU for distributors serving mixed Japanese and Chinese light commercial fleets. Confirm the vehicle-specific OEM reference against the original part marking for final fitment verification.

• Bore Diameter Verified: 3/4-inch (19.05 mm) — confirmed by Dorman CM123692 ("Bore Size: 0.75""), Brettstruck ("Bore Ø (inch): 3/4"; Bore Ø (mm): 19.05"), and Thai brake supplier ("SIZE: 3/4"").
• Vehicle & Engine Coverage Verified: NKR55 (2.8L, Jan 85–Dec 98), NHR55 (2.8L, Jan 88–Dec 98), NPR58 (3.6L, Jan 85–Dec 98), NPR59 (4BD1), NPR66 (4HF1) — confirmed by Brettstruck fitment data. 4JB1 engine association confirmed by MAMUR/IZUMI supplier listings.
• Cross-Brand Coverage Verified: JAC 6700 and JMC 1030/1040 — confirmed via JAC OEM 1602100Z2-1107. Chevrolet/GMC W-Series (1987–1995) — confirmed by Dorman application data.
• Brand & Certification Verified: MAMUR (M-3817), IZUMI, ISO/TS16949 — confirmed by supplier listings and French portal data.
• Weight & Volume Verified: 0.8 kg net weight; 0.0017 m³ volume — confirmed by MAMUR supplier data.
• Cross-Reference Density Verified: 8-97048-567-0, 8970485670, 8-97032832-0, 8970328320, 8-97032-833-0, 8-94312-902-0, 8-94312-903-0, 8-94441-512-0, 8-94463-247-1, 8-94463-248-1, 1602100Z2-1107 (JAC) are consistently grouped as interchangeable or related references across Dorman, Brettstruck, MAMUR, and DEAUTO catalogs.
• Brand Cross-Reference Verified: Dorman CM123692, NAP/CMC, Axcel, SANYCO, FIC FM6208, TRW PND185, Valeo 4011541 — confirmed as aftermarket equivalents for the 8970485670 application.

• Clutch pedal sinks to the floor or feels spongy: Internal seal failure allows hydraulic pressure to bypass, preventing full clutch disengagement — the most common symptom of a failing master cylinder.
• Difficulty selecting gears / gear clash: Insufficient hydraulic pressure means the clutch does not fully disengage, causing hard shifting and gear grinding.
• Fluid leak at the master cylinder body or pushrod end: External seal failure allows clutch fluid to escape, often visible as wetness under the dashboard or on the firewall.
• Fluid level dropping in the clutch reservoir without an external leak: Internal seal bypass can allow fluid to enter the pushrod boot area or the cabin.
• Clutch pedal does not return fully: A worn internal spring or seal can prevent the pedal from returning to its rest position.
• Contaminated or dark clutch fluid: Degraded fluid accelerates seal wear and can indicate internal master cylinder degradation.

• Bore is the first check: This master cylinder is 3/4-inch (19.05 mm). Confirm the original unit's bore before ordering — a mismatched bore changes pedal effort and release travel.
• NKR55 / NPR58/59 confirmed: The core applications are NKR55, NHR55, NPR58, NPR59, and NPR66. Other N-Series variants (e.g., NKR66 4HF1, NQR71) may use different references. Provide the VIN for final confirmation.
• Reservoir inclusion varies: Some channels include the reservoir; others supply the cylinder only. Confirm package contents at inquiry.
• Cross-brand ISUZU / JAC / JMC / GM coverage: This master cylinder serves ISUZU, JAC, JMC, and Chevrolet/GMC W-Series applications. Confirm the vehicle-specific OEM reference against the original part marking for final fitment verification.

1. Confirm the required part first: Verify the original master cylinder's bore diameter (19.05 mm) and whether the reservoir is to be reused. Compare the pushrod length and mounting configuration.
2. Bench-bleed the master cylinder: Clamp the cylinder in a vice with soft jaws and bleed it on the bench before installation to reduce in-vehicle bleeding time.
3. Disconnect the battery and hydraulic line: Disconnect the negative battery terminal. Place a drain pan underneath, disconnect the clutch line from the master cylinder outlet, and plug the line immediately to prevent contamination.
4. Remove the old master cylinder: From inside the cabin, remove the clevis pin connecting the pushrod to the clutch pedal. From the engine bay, unbolt the master cylinder from the firewall or pedal bracket.
5. Transfer the reservoir (if applicable): If the replacement is supplied without a reservoir, carefully transfer the original reservoir and seals.
6. Install the new master cylinder: Position the 8-97048567-0 cylinder, insert the mounting bolts, and torque to the workshop manual specification. Do not over-torque the hydraulic line fitting.
7. Reconnect the pushrod and hydraulic line: Reconnect the clevis pin to the clutch pedal. Connect the hydraulic line and tighten to specification.
8. Bleed the clutch system: Fill the reservoir with the specified clutch fluid and bleed the system according to the ISUZU procedure until clear, bubble-free fluid flows from the slave cylinder bleeder screw. Air in the circuit is the leading cause of post-replacement clutch drag.
9. Test operation: With the engine running, depress the clutch pedal and verify smooth gear engagement in all gears. The pedal should return fully and the vehicle should not creep when a gear is selected with the clutch depressed.

• Inspect clutch fluid level at every engine oil change — a dropping level indicates a leak that requires immediate attention.
• Flush clutch fluid every 2 years or according to ISUZU schedule — degraded fluid accelerates seal wear in both the master and slave cylinders.
• Check for leaks at the master cylinder body, outlet fitting, and reservoir seal during routine inspection.
• Replace the master cylinder at the first sign of a spongy pedal or external leak — do not "top up and monitor" a known-failing hydraulic component on a commercial truck.

• Standard packing: MAMUR package / neutral packaging — confirmed by MAMUR supplier terms. Bulk export carton available.
• Package contents: 1 × Clutch Master Cylinder Assembly. Reservoir inclusion varies — confirm at inquiry. Mounting hardware, pushrod, and clutch fluid are not included unless explicitly stated.
• Set options: Cylinder only (standard) / cylinder + reservoir (where available) — specify at inquiry.
• Suitable for: ISUZU NKR55 / NPR58 / NPR59 / NPR66 clutch repair shops, JAC 6700 / JMC 1030 service providers, Chevrolet/GMC W-Series maintenance departments, light commercial fleet maintenance, spare parts distributors, and export wholesalers.