Brake Master Cylinder Assembly 8-97171710-0 8971717100 For ISUZU NKR NPR ELF NKR71 NKR81 NPR72 — OEM Verified Direct Fit, Hydraulic Assist Brake Master, 1998–2009

The Brake Master Cylinder Assembly with OEM references 8-97171710-0 / 8971717100 is a verified replacement hydraulic brake master cylinder for ISUZU NKR, NPR, and ELF series trucks from 1998 to 2009. This assembly is the hydraulic assist type ("ハイドロ アシスト ブレーキ" / гидро-ассист) brake master cylinder, responsible for converting pedal force into hydraulic pressure that actuates the front and rear brake circuits.

The part is confirmed across ISUZU ELF / NKR81E, NKR71EP, and NPR72PYR chassis applications, covering engines including 4HF1 (4.3L), 4HG1 (4.6L), 4HL1 (4.8L), and 4HJ1 (5.0L) diesel units. It is cataloged by Japanese and Russian ISUZU parts specialists as a "Master Cylinder Assembly; Brake" and "Главный тормозной цилиндр NKR/NPR 98-09г.", confirming its role as the brake master cylinder — not a clutch component.

• Part Type Verified: Confirmed as Brake Master Cylinder Assembly by Japanese (モノタロウ "マスタ シリンダ アセンブリ；ブレーキ"), Russian ("Главный тормозной цилиндр"), and multiple independent catalogs.
• Vehicle Coverage Verified: Confirmed for ISUZU ELF NKR81E, NKR71EP, and NPR72PYR chassis, with engine coverage including 4HF1, 4HG1, 4HL1, and 4HJ1.
• Year Range Verified: Russian parts catalog explicitly lists "NKR/NPR 98-09г." (1998–2009) for 8971717100.
• Hydraulic Assist Type Verified: Multiple Japanese catalog entries describe the part as "ハイドロ アシスト ブレーキ" (hydraulic assist brake), distinguishing it from conventional vacuum-boosted master cylinders.
• Cross-Reference Lead Verified: 897118-6981 / 8-97118698-1 is listed alongside 897171-7100 / 8-97171710-0 as a cross-reference in an ISUZU parts distributor catalog. 8971484320 is also listed as a paired reference on one supplier page.
• Bore Diameter NOT Publicly Published: ISUZU OEM parts systems and authorized distributors do not disclose dimensional specifications for this part number. Independent listings for adjacent N-Series master cylinders show 1-1/8", 1-1/4", and 1-3/8" bore variants, confirming that bore size is a critical variable that must be verified physically.

• Spongy or sinking brake pedal: The most common symptom of a failing master cylinder. The pedal may slowly sink to the floor when held under pressure, indicating internal seal bypass.
• Brake fluid leak at the master cylinder body or rear seal: Visible wetness or dripping at the pushrod end or between the reservoir and cylinder body — external seal failure.
• Brake fluid loss without an external leak: Fluid may be entering the brake booster (on vacuum-assisted systems) or accumulating inside the firewall area — a sign of internal seal failure.
• Uneven or dragging brakes: A master cylinder that cannot build or release pressure correctly can cause one circuit to drag or fail to apply fully.
• Brake warning light illumination / low pedal: Insufficient hydraulic pressure can trigger the brake warning lamp and reduce braking effectiveness.
• Contaminated or discolored brake fluid: Dark, cloudy, or particulate-laden fluid often accompanies internal master cylinder degradation and can accelerate seal failure.

• Part type must be confirmed first: This is a brake master cylinder, not a clutch master cylinder. Despite some Chinese B2B listings labeling it as "离合器总泵", the preponderance of Japanese and Russian ISUZU parts data confirms it as a brake master cylinder assembly. If the vehicle requires a clutch master cylinder, do not use this part number.
• Bore size is the critical unknown: Public sources do not disclose the bore diameter for 8-97171710-0. Adjacent N-Series master cylinders use 1-1/8", 1-1/4", and 1-3/8" bores. A sample order or physical comparison against the original unit is strongly recommended before bulk purchasing.
• Hydraulic assist vs. vacuum assist: This part is the hydraulic assist type. Vehicles equipped with a vacuum booster use a different master cylinder configuration. Confirm the brake assist type on the vehicle before ordering.
• Reservoir inclusion: Some suppliers ship the master cylinder with the reservoir, others without. Clarify reservoir inclusion at inquiry — a missing reservoir means the vehicle cannot be returned to service until one is sourced.

1. Confirm part type and bore: Before installation, compare the new master cylinder to the original unit. Verify bore diameter, port thread, reservoir mounting, and pushrod length. This is the most critical step given the limited public specification data.
2. Bench-bleed the master cylinder: Clamp the master cylinder in a vice (with soft jaws) and bleed it on the bench before installation. This removes trapped air from the cylinder and reduces in-vehicle bleeding time.
3. Disconnect the battery and brake lines: Disconnect the negative battery terminal. Place a drain pan under the master cylinder and disconnect the brake lines. Plug the lines immediately to prevent contamination and fluid loss.
4. Remove the old master cylinder: Unbolt the master cylinder from the brake booster or hydraulic assist unit. Note the orientation of the pushrod and any spacers.
5. Inspect the brake booster / assist unit: Check the booster pushrod for wear and the mounting surface for damage. A damaged booster can destroy a new master cylinder.
6. Install the new master cylinder: Position the new unit, connect the brake lines, and torque the mounting bolts to the workshop manual specification. Do not over-torque the hydraulic line fittings.
7. Bleed the brake system: Bleed the front and rear circuits according to the ISUZU procedure. Hydraulic assist systems may require specific bleeding sequences — confirm against the workshop manual for the exact chassis.
8. Test pedal feel and brake function: The pedal should be firm and should not sink under sustained pressure. Road-test at low speed before returning the vehicle to service.

• Inspect brake fluid at every service — contaminated or dark fluid accelerates master cylinder seal wear.
• Replace brake fluid every 2 years or according to ISUZU schedule.
• Check for leaks at the master cylinder body, line fittings, and reservoir seal during routine inspection.
• Replace the master cylinder at the first sign of a sinking pedal or external leak — do not "monitor" a known-failing brake component on a commercial vehicle.

• Standard packing: Neutral carton with protective port caps; wooden pallet available for bulk export orders.
• Package contents: 1 × Brake Master Cylinder Assembly (reservoir inclusion varies — specify at inquiry).
• Set options: Master cylinder only / master cylinder + reservoir — specify at inquiry.
• Minimum order: 1 pc (sample) / bulk quantity pricing available. Sample order is strongly recommended for bore verification.
• Suitable for: ISUZU NKR/NPR/ELF brake system repair shops, fleet maintenance departments, spare parts distributors, and export wholesalers serving Southeast Asia, the Middle East, Africa, and Latin America.
• Related parts available: Brake booster / hydraulic assist unit, brake fluid, brake lines, wheel cylinders, and brake shoes for the NKR/NPR platform.