Brake Master Vac Assembly 8-98006788-0 8980067880 For ISUZU D-MAX 2007–2011 2.5D 3.0D 4JA1 4JJ1 — Genuine 1.5-Chamber Vacuum Booster, Direct Bolt-On Replacement

The Brake Master Vac Assembly with OEM references 8-98006788-0 / 8980067880 is a verified direct-fit vacuum brake booster for ISUZU D-MAX pickups produced from 2007 to 2011. This assembly is the vacuum-assisted servo unit that multiplies driver pedal force to reduce braking effort. It mounts in the engine compartment and attaches to the brake master cylinder with mounting screws and brackets.

Its function is to amplify braking force, making the pedal easier and less tiring to press, resulting in shorter stopping distances and more responsive braking.

This unit is specifically a 1.5-chamber (1½-layer) vacuum booster ("ขนาด 1 ชั้นครึ่ง"), a specification that provides a larger vacuum chamber than a standard single-chamber booster, delivering noticeably softer pedal effort and shorter braking distance — particularly suitable for loaded or heavy-duty use. It is cataloged under the ISUZU OEM description "MASTER VAC ASM; BRK" and is supplied as a complete booster assembly — not a master cylinder alone and not a repair kit.

• Genuine 1.5-Chamber Specification Verified: Confirmed as "ขนาด 1 ชั้นครึ่ง" (1.5-chamber) genuine ISUZU OEM booster for D-MAX 2007–2011, offering superior vacuum amplification versus standard single-chamber units.
• OEM Description Verified: Cataloged as "MASTER VAC ASM; BRK" — confirming it is the brake vacuum booster assembly, not a master cylinder or a repair kit.
• Vehicle Coverage Verified: Confirmed for ISUZU D-MAX 2007–2011, covering variants including Gold Series, Platinum, and Super Platinum for the 2007–2011 model window.
• Engine Association Verified: Reference engine model 4JA1 confirmed in supplier data; additional coverage for 4JJ1 and related D-MAX diesel variants exists in the platform.
• Material Verified: Metal construction, capable of maintaining performance under high temperature, high humidity, and frequent vibration conditions in the engine bay.
• Installation Configuration Verified: Mounted in the engine compartment, fixed to the brake master cylinder with mounting screws and brackets — direct bolt-on to the factory mounting points with matching air pipe and pedal pin specifications, requiring no system modification.
• Weight & Size Reference Verified: Net weight references of approximately 3.6–4.4 kg depending on packaging; packaging size around 245 × 250 × 245 mm to 255 × 255 × 320 mm.
• Cross-Reference Lead Verified: 8973655180 and 8973015350 appear in related D-MAX / TFS brake booster listings, providing alternative sourcing leads for this functional family.
• Warranty Reference: 6 months (China aftermarket standard) to 1 year (Kowze supplier reference) — confirm tier at inquiry.

• Hard brake pedal / excessive pedal effort: The most common symptom. The booster no longer amplifies pedal force, requiring heavy stomping to stop the vehicle — a direct sign of diaphragm or vacuum chamber failure.
• Hissing or air-leak noise from under the dashboard / engine bay: A ruptured diaphragm or failed check valve allows vacuum to escape, producing a persistent "fsss" or hissing sound.
• Longer stopping distance / delayed brake response: Insufficient vacuum assist means the brakes engage later and with less force, extending stopping distances, especially noticeable in loaded or emergency situations.
• Brake pedal does not return / slow return: A booster with internal valve damage can prevent the pedal from returning quickly, affecting drivability and safety.
• Intermittent power assist loss: Vacuum leaks can cause the assist to fade after the first pedal application, requiring repeated pumping to maintain braking force.
• Rough idle or engine stumble when braking: A failed booster diaphragm can allow unmetered air to enter the intake manifold on vacuum-assisted systems, disrupting idle quality.

• "Vac Assembly" vs. "Master Cylinder": This is the vacuum booster assembly, not the brake master cylinder. If the original master cylinder is also worn or leaking, it must be ordered separately. Confirm the required scope before ordering.
• 1.5-Chamber vs. Standard 1-Chamber: This is specifically the 1.5-chamber specification, which provides greater vacuum amplification than a conventional single-chamber booster. Do not substitute a standard single-chamber unit if the original is 1.5-chamber — pedal effort and braking feel will be adversely affected.
• Engine association: Supplier data primarily associates this booster with the 4JA1 engine, while the D-MAX 2007–2011 platform also includes 4JJ1 variants. Confirm the engine code and VIN before ordering, especially for fleet applications where mixed engine types may exist.
• Model year boundary: The confirmed application window is 2007–2011. Later D-MAX generations (2012+) may use a different booster specification. Do not assume interchangeability across model years.

1. 1Confirm the required scope first: Verify that the original unit is the vacuum booster assembly, not the master cylinder alone. Confirm that the replacement is the 1.5-chamber specification where applicable.
2. 2Safety first: Park on level ground, engage the parking brake, and chock the rear wheels. Disconnect the battery negative terminal.
3. 3Depressurize the brake system: If the master cylinder is being removed or disconnected, relieve hydraulic pressure according to the workshop manual procedure.
4. 4Disconnect the vacuum source and check valve: Remove the vacuum hose from the booster check valve. Note the orientation for reassembly.
5. 5Disconnect the master cylinder: Unbolt the master cylinder from the booster. Support the master cylinder to avoid stressing the brake lines. Plug the lines if fully removed.
6. 6Remove the clevis pin from the brake pedal: From inside the cabin, remove the clevis pin connecting the booster pushrod to the brake pedal arm.
7. 7Remove the booster mounting bolts: From the engine bay, unbolt the booster from the firewall or pedal bracket. Extract the booster carefully.
8. 8Transfer components: If the original booster carries a check valve, gasket, or boot that is not included with the replacement, transfer it to the new unit.
9. 9Install the new booster: Position the 8-98006788-0 booster onto the firewall. Install the mounting bolts and torque to specification.
10. 10Reconnect the pushrod and master cylinder: Reconnect the clevis pin to the brake pedal. Reattach the master cylinder to the booster and torque the mounting nuts to specification.
11. 11Reconnect the vacuum hose and check valve: Ensure the check valve is oriented correctly and the hose is fully seated.
12. 12Bleed the brake system (if hydraulic lines were opened): Bleed the brakes according to the ISUZU procedure until clear, bubble-free fluid flows.
13. 13Test operation: With the engine running, depress the brake pedal and verify that assist is present (pedal should be noticeably easier to press than with the engine off). Check for hissing noises that would indicate a vacuum leak. Road-test at low speed before returning the vehicle to service.

• Inspect the booster vacuum hose and check valve at every brake service or every 20,000–30,000 km — a cracked hose or stuck check valve can mimic booster failure.
• Check for pedal feel changes during routine driving — a progressively hardening pedal indicates declining booster performance.
• Replace the booster at the first sign of hissing, hard pedal, or delayed assist — do not "monitor" a known-failing safety component on a commercial or passenger vehicle.
• Use only the specified 1.5-chamber booster if the original vehicle is so equipped — substituting a different chamber configuration alters braking feel and performance.

• Standard packing: Neutral carton with protective internal cushioning; bulk export pallet available.
• Package contents: 1 × Brake Master Vac Assembly (Vacuum Booster). Master cylinder, check valve, vacuum hose, and mounting hardware may or may not be included — confirm exact package contents at inquiry.
• Set options: Booster only / booster + master cylinder combination (where available) — specify at inquiry.
• Suitable for: ISUZU D-MAX brake system repair shops, pickup fleet maintenance departments, spare parts distributors, and export wholesalers serving Southeast Asia, the Middle East, Africa, and Latin America.
• Related parts available: Brake master cylinder, vacuum check valve, vacuum hose, brake fluid, and complete D-MAX brake system service kits.