One of the more important aspects of the swap is upgrading the Master Cylinder. The pedal feel on the 240SX is weak with the stock brakes, but feels even worse with 12 pistons worth of brakes. In order to do the swap, all you will need is the master cylinder from a 300ZX. The proportioning between a turbo 300ZX and NA 300ZX is the same. If there is any concern, make sure to pick up the master cylinder that works with the calipers you are using. The brake booster is not necessary although it is a worthy addition.
There are a few different options from which to choose. Check out the parts listing page for the details. The 17/16″ MC with a manual trans equipped 240 brake booster can be a bit stiff. The manual trans equipped 240 has a smaller stock MC than an automatic equipped 240SX. The automatic equipped 240SX brake booster offers more assistance. Using the automatic’s booster along with either the 1″ or 17/16″ MC will offer the same advantages of a larger MC but with an easier pedal.
Another options is to swap the 300ZX booster along with the master cylinder. See the end of this write-up for details.
One of the questions that always comes up is the proportioning of the 300ZX MC vs the 240’s MC and the effect of using the 300ZX MC with stock 240 rear brakes. Below are a few excerpts from FreshAlloy members:
The way OE proportioning valves work is that the front and rear line pressures go up by the same amount until the pressure reaches the so-called “split point”. At this point, the rear pressure increases at a lower rate than the front pressure (with the proportionality factor given by the reducing ratio).
Now the reducing ratio for the Z32 and 240sx MC’s are the same (0.4), so the only difference is the split point. The Z32’s split point is lower than the 240sx, so above the split point, the Z32’s rear line pressure will always be lower than that of the 240sx.
What this is saying, is that there is no way the rear brakes are going to lock up first by swapping in a 300ZX MC while using Z32 front brakes and stock 240 brakes in the rear.
All that said, I chose the 1 1/16″ MC for my swap.
- Master Cylinder
- Brake Booster (optional, read below)
- Brake Fluid
- Jack and Jack Stands
- Metric sockets and wrenches
- 10 mm Metric Flare Nut Wrench (optional but useful)
- Allen Drives
- Cutting tool (Dremel, air cutoff, etc)
- Hammers and a small punch
- Flaring tool
Please note, there are multiple combinations of parts that will give you the results for which you are looking. A brake booster from either a 300ZX or an automatic equipped 240SX will give more assist requiring less pedal effort. I have received emails from people that complained about the pedal effort being too high when using the 17/16″ MC. Using the smaller MC’s or bigger boosters will help reduce pedal effort while maintaining the better pedal feel of the upgrade.
Also, you may want to consider using a 15/16″ MC (if you had the 7/8″) for a mild improvement with no modifications necessary.
If you have ABS, you do not have to remove the plug. In that case, skip to the master cylinder installation.
You will notice that the plugged hole is missing the proper flare fitting. You have two options to resolve this issue, the first is a rather simple fix. You will need to find a bubble flare tool to put a flare in the line that will work without the missing fitting.
Before you install the master cylinder, take a moment to flush the reservoir with brake cleaner. This will not be necessary with a new master cylinder.
Before adding any fluid, attach the plug and make sure that the brake light on the dash stays lit when the ignition is turned on. After adding fluid, make sure the light turns off.
If the master cylinder is the only modification you are doing, you will need to thoroughly bleed the brakes. Start by gravity bleeding the entire system, and then use your favorite method of bleeding to finish the job.
FYI: Gravity bleeding is the process of opening all of the bleeders and letting the fluid drain out. This is especially helpful when you’ve installed a new master cylinder.
Note: Doriftomodachi from Zilvia.net discovered that is possible to swap the fluid reservoir from the original master cylinder. Swapping the reservoir allows you to use the original fluid level wiring without having to splice wiring.
During the intro I noted the option of swapping the 300ZX booster along with the master cylinder. I never had a chance to do it myself but I have spoken to those that have. Dave Coleman of Sport Compact Car and MotoIQ fame performed the swap on his project car.
The master cylinder swap isn’t a necessary component for a successful brake swap however the improvement in pedal feel and brake control is a worth while effort that ties all of the work together.
The next sections will cover the part numbers and brake swap alternatives. Click the link below for the complete series.