Brake Master Cylinder Assembly 8-97038427-1 8970384271 For ISUZU TFR TFS 4JA1 4JB1 (1991–1999) — Ø23.8mm Piston Bore, Without Sensor, OEM-Spec Aftermarket

The Brake Master Cylinder Assembly with OEM references 8-97038427-1 / 8970384271 is a verified direct-fit replacement for the ISUZU TFR and TFS pickup platform, covering the 1991–1999 production window with 2.3L, 2.8D, and 2.8D 4WD engine configurations. This master cylinder is the hydraulic pressure generator at the heart of the braking system — it converts pedal force into hydraulic pressure that is transmitted to the wheel cylinders, engaging the brakes at all four corners.

This unit is specifically the "without sensor" (ohne Sensor / sans capteur) variant, meaning it does not include the brake fluid level sensor or its wiring provision. This is a critical distinction on the TFR/TFS platform, as some variants use a sensor-equipped master cylinder. The piston bore diameter is 23.8 mm, confirmed by the TRW PMK858 cross-reference for the same TFR/TFS application. Reference net weight is 0.646 kg, and the unit is supplied as 1 PCS per pack.

• Piston Bore Verified: 23.8 mm — confirmed by TRW PMK858 cross-reference for the ISUZU TFR/TFS Pickup application, listing "Piston Ø: 23,8 mm".
• Sensor Configuration Verified: Without sensor — confirmed by German supplier listing "3505100D Hauptbremszylinder fur Isuzu TFR - ohne Sensor" for the same TFR application.
• Net Weight Verified: 0.646 kg — confirmed by isuzureplacementparts.com listing for 8-97038427-1.
• Vehicle & Engine Coverage Verified: ISUZU TFR/TFS Pickup, engines 2.3, 2.8 D, 2.8 D 4WD, model years 1991–1999 — confirmed by TRW PMK858 application data.
• Cross-Reference Density Verified: 8-97038427-1, 8970384271, 8-97038427-0, 8970384270, 3505100D, 97038247 are consistently grouped across isuzureplacementparts.com, Feimenlmugol, Persian ISUZU parts portals, and TRW catalog data.
• OEM Association Verified: 3505100D is listed as an associated OE reference for the ISUZU TFR brake master cylinder family, with 4JA1 engine association confirmed by multiple Yishan portal listings.
• TRW Cross-Reference: TRW PMK858 provides a verifiable European aftermarket alternative for the TFR/TFS application, confirming the 23.8 mm bore specification.
• Warranty & Packaging Vary by Supplier: Warranty references range from 3 months (isuzureplacementparts.com) to 6 months (Feimenlmugol / Xutlin) — confirm tier at inquiry. Packaging options include neutral box, color box, and customer-branded packaging.

• Sinking brake pedal at a stop: The most classic symptom — the pedal slowly creeps toward the floor while holding steady pressure at a traffic light, indicating internal seal bypass within the master cylinder.
• Spongy pedal that persists after bleeding: Air enters the system through a failed seal, and no amount of bleeding permanently removes the sponginess.
• Inconsistent pedal feel: The pedal may feel normal on one application and low or soft on the next, as the internal seals intermittently fail to hold pressure.
• Brake warning light illumination (without low fluid): A failing master cylinder can trigger the brake warning lamp even when the reservoir is at the correct level.
• Fluid weeping between the master cylinder and brake booster: External seal failure allows brake fluid to escape at the rear of the cylinder, often visible as wetness or paint damage on the booster.
• Longer stopping distances / need to pump the pedal: As pressure retention degrades, the driver must pump the brake pedal repeatedly to build sufficient braking force.

• Sensor configuration is the first check: This is the without sensor variant. If the original master cylinder has a brake fluid level sensor connector, do not install this unit — order the sensor-equipped variant instead. Mismatching the sensor configuration will leave the brake warning system inoperative.
• Bore size (23.8 mm) must match: The 23.8 mm piston bore is confirmed by the TRW PMK858 cross-reference. A different bore size will alter pedal effort and braking balance. Confirm the original unit's bore specification where possible.
• Model year boundary (1991–1999): This master cylinder is confirmed for the 1991–1999 TFR/TFS window. Later TFR facelifts (1999+) and the D-MAX (2002+) use different master cylinder references. Do not assume interchangeability across model years without VIN confirmation.
• 8-97038427-1 vs. 8-97038427-0: The -1 suffix is the user's primary reference and the confirmed isuzureplacementparts.com listing. 8-97038427-0 is grouped as an associated reference for the same TFR application. These are functionally interchangeable for the same master cylinder position — read the original unit's marking where possible.
• Cross-reference caution with 8970382470: The TRW PMK858 catalog lists OE number 8970382470 as a "similar" reference. This is digitally similar but not identical to the user's 8970384271. Do not treat these as interchangeable without confirming the physical bore and sensor configuration against the original unit.

1. 1Confirm the required variant first: Verify that the original master cylinder is the without-sensor type and that the bore diameter matches 23.8 mm. Compare the port configuration and reservoir mounting to the replacement.
2. 2Bench-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. 3Disconnect 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. 4Remove the old master cylinder: Unbolt the master cylinder from the brake booster. Note the orientation of the pushrod and any spacers.
5. 5Inspect the brake booster: Check the booster pushrod for wear and the mounting surface for damage. A damaged booster can destroy a new master cylinder.
6. 6Install the new master cylinder: Position the 8-97038427-1 unit, connect the brake lines, and torque the mounting nuts to the workshop manual specification. Do not over-torque the hydraulic line fittings.
7. 7Bleed the brake system: Bleed the front and rear circuits according to the ISUZU procedure until clear, bubble-free fluid flows from each bleeder screw.
8. 8Test 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 pickup.

• Standard packing: Neutral box / Color box / Customer-branded packaging. Pack quantity: 1 PCS.
• Package contents: 1 × Brake Master Cylinder Assembly. Reservoir, sensor (not applicable for this variant), and mounting hardware may or may not be included — confirm exact package contents at inquiry.
• Suitable for: ISUZU TFR/TFS brake system repair shops, light commercial fleet maintenance departments, spare parts distributors, and export wholesalers serving Southeast Asia, the Middle East, Africa, and Latin America.
• Related parts available: Brake booster, wheel cylinders, brake shoes, brake fluid, and complete TFR/TFS brake system service kits.