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MPA Electrical B3121 Power Brake Booster
Vacuum Brake Booster for Pathfinder and QX4
Restore consistent brake assist with this remanufactured vacuum power brake booster from MPA Electrical. Part number B3121 is built for 2001 Nissan Pathfinder and 2001 INFINITI QX4 applications, helping reduce pedal effort and improve braking response in daily driving.
Key Features
- Remanufactured vacuum power brake booster
- Standard replacement brake service grade
- 10.58 in. diaphragm diameter for vacuum-assisted braking
- Metal housing for durable brake system service
- 2 mounting studs with 8 x 1.25 mm master cylinder stud thread size
- Master cylinder not included
- Brake pedal rod extension not included
- Mounting bracket, gasket or seal, and front seal not included
Product Line Details
MPA Electrical reman brake boosters are rebuilt with replacement and specially treated components to help maintain vacuum sealing and pressure transfer. Each unit is 100% end-of-line tested with proprietary equipment to verify braking assist performance before release.
Detailed Description
MPA Electrical B3121 is a remanufactured vacuum power brake booster designed for direct replacement in 2001 Nissan Pathfinder and 2001 INFINITI QX4 models. It is engineered to deliver strong vacuum assist with minimal pedal effort, making it a practical choice when the original booster shows signs of wear, vacuum loss, or reduced braking response. This B3121 booster is supplied without the master cylinder, so it is intended for service where the existing master cylinder is retained or replaced separately.
This part cross-references Nissan 472103W410 for the same application.
What It Helps Fix
- Hard brake pedal feel
- Reduced vacuum assist during braking
- Longer stopping effort caused by booster wear
- Brake response issues related to vacuum seal loss
- Service replacement needs on Pathfinder and QX4 brake systems
Installation Notes and Tips
Verify master cylinder stud thread size, mounting stud layout, and booster depth before installation. Because the master cylinder is not included, inspect the existing master cylinder, pushrod interface, and vacuum hose condition during service. Confirm fitment for 2001 Nissan Pathfinder and 2001 INFINITI QX4 before ordering, and bleed the brake system after any related hydraulic work.
Quality Assurance
Each MPA Electrical reman brake booster is subjected to 100% end-of-line testing using proprietary test equipment to confirm vacuum seal integrity and pressure transfer performance.
| Brand | MPA Electrical |
|---|---|
| Part Number | B3121 |
| Position | Reman Vac Pwr Brake Booster w/o Master Cyl |
| Brake Service Grade | Standard replacement |
| Booster Type | Vacuum |
| Brake Pedal Rod Extension Included | No |
| Master Cylinder Included | No |
| Gasket Or Seal Included | No |
| Housing Material | Metal |
| Diaphragm Diameter | 10.58 |
| Diaphragm Diameter | 268.73 |
| Mounting Bracket Included | No |
| Front Seal Included | No |
| Master Cylinder Stud Thread Size (mm) | 8 x 1.25 |
| Mounting Stud Quantity | 2 |
| Product Condition | Remanufactured |
This part fits 2 vehicles. Search below:
| Year | Make | Model | Position | Notes |
|---|---|---|---|---|
| 2001 | INFINITI | QX4 | N/A | Reman Vac Pwr Brake Booster w/o Master Cyl |
| 2001 | Nissan | Pathfinder | N/A | Reman Vac Pwr Brake Booster w/o Master Cyl |
* Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.
This part directly replaces or is cross-referenced with the following part numbers:
Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.