The 300ZX master cylinder is a common upgrade for those looking for superior pedal response or a larger bore master cylinder for big brake upgrades. But what most people don’t realize is that there is more than one way to swap a 300ZX master cylinder, because there’s quite a few versions available.

When upgrading to larger brakes or bigger calipers like our Evolution IX brakes on a S14 guide will show you, this master brake upgrade is a must. Before we delve into how to upgrade to a 300ZX brake master cylinder, let’s look at the differences between the parts available.

Unlike the clutch master cylinder upgrade, the brake master is a bit easier so long as you plan ahead. Simply purchasing a 300zx master cylinder isn’t the end to your planning when it comes to upgrading.

Because of the 300ZX’s third brake line fitting located in the middle of the 300ZX, you will need to get creative in order to terminate your brake lines properly. If your S14 240SX already has ABS equipped, there is no need to address this section, as it does not pertain to you.

However if you do not have ABS in your 240SX, you will need to plan accordingly to get either a bubble flare fitting inside the third brake like port, or terminate it using a banjo bolt and 12mmx1.25 female hose end.

Removal of the third brake fitting can prove difficult because it can be a five sided hex fitting, depending on the 300ZX master cylinder you have. Try to get creative if your brake master cylinder came equipped with this five sided fitting.

But once you remove the third brake fitting, you will see that the bubble flare inside is missing.

You can do one of three things when it comes to the solution for the third brake fitting. Firstly you can purchase a custom 300ZX brake master with this brake fitting already installed. This makes the task of bending your stock brake line around and screwing it in much much easier.

Solution 2 is you can either purchase a pack of these inverted bubble flares and simply insert into the third brake fitting. Importnut.net suggests hacking apart a sacrifical 240SX master cylinder to obtain the inverted bubble flare.

While we won’t suggest that extreme a method, we do suggest either picking up a bubble flare kit. There are also universal brake lines in the stock S14 size that you can take to a specialist to have them flare the line to accept that middle brake port.

Of course if this step is too difficult in our how to upgrade to a 300ZX brake master cylinder walkthrough, you can always take the lazy way out.

To adapt the third brake line fitting, you will need a few parts :

• m10 banjo bolt fitting
• Russell 65702 – banjo straight to 10mm female -3 AN
• Aeroquip FCM2945 – -3 male to 10mm x 1.0 inverted flare

Take your M10 banjo bolt fitting and insert through your Russell banjo to female -3AN fitting. Make sure you use copper crush washers on BOTH SIDES of your banjo bolt fitting. The Aeroquip FCM2945 will help you terminate to a 10mm x1.0 inverted flare which will accept your passenger side front brake line.

You can also eliminate the Russell fitting by incorporating a Aeroquip FCM2974, a female -3 AN to 10mm x1.0 inverted flare, and use something like this.

This solution isn’t ideal and it sure doesn’t look pretty, but it works and will not create an imbalance in braking pedal pressure or effort. Simply put this solution is the easiest out of the three options in our how to upgrade to a 300ZX brake master cylinder guide.

Differences between the 300ZX Master Cylinders

Bore Size

15/16” 300ZX Master Cylinder Part numbers – 46010-30P10 Manufacture date 2/89 – 7/90

17/16” 300ZX Master Cylinder Part numbers

• 46010-30P02 Manufacture date 7/89 – 7/90
• 46010-30P02 Manufacture date 7/90 – 2/91
• 46010-30P21 Manufacture date 2/89 – 7/90
• 46010-30P22 Manufacture date 7/89 – 7/90
• 46010-31P22 Manufacture date 7/90 – 2/91

1” 300ZX Master Cylinder Part numbers

• 46010-45P00 Manufacture date 9/91 – 9/93
• 46010-45P00 Manufacture date 2/91 – 9/91
• 46010-45P20 Manufacture date 9/91 – 9/93
• 46010-45P20 Manufacture date 9/93 – 8/95

You should also be cognizant of the differences between the brake booster for the S14 equipped with automatic or manual transmissions. The automatic KA24DE comes with a slightly larger or thicker brake booster, so be aware for any engine swaps that may require special spacing requirements.

Brake level sensor wiring

Nearing the end of our how to upgrade to a 300ZX brake master cylinder guide, and it’s time to wire in the brake fluid level sensor. This sensor can be reused and will not need modification, if you have an existing 240SX master cylinder reservoir that will fit your 300ZX one.

Simply transplant the reservoir and double check for any leaking before plugging in your brake fluid level sensor. For the rest of us, you must do this step near the end of our writeup.

Make sure to cut and wire in your brake fluid level sensor, but do not solder them until you know for a fact the sensor is working correctly. You should wire this sensor in before filling your brake master cylinder with brake fluid. Turn the key to the “ON” position and monitor your dash lights for the low brake fluid signal.

With your wiring already in place, begin to fill your 300ZX brake master cylinder and make sure that the light turns off accordingly. If your light turns off and there are no leaks, you can begin the lengthy process of bleeding your braking hydraulics.

Always start with your rear brakes and make your way forward. Have a friend double and triple check your work, which you should have already double checked for any leaks or any moisture.

Congratulations, you have now completed our how to upgrade to a 300ZX brake master cylinder article. Please leave us any questions or comments below.