Wilwood Brake Tandem Master Cylinder Install

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Wilwood Brake Tandem Master Cylinder Install

Postby Ryan @ GWR » Tue Jul 07, 2015 4:28 pm

Installation guide for our Wilwood Brake Master Cylinder kit with tandem reservoirs for the 1990-2005 Miata
Link to our store: http://www.good-win-racing.com/Mazda-Performance-Part/61-1699.html

Here's a look at what's included in our kit:


A) Wilwood twin reservoir master cylinder
B) 2x Plastic fittings and clear tubing for bench bleeding process
C) Brake booster adapter bracket
D) Straight union fitting (Metric)
E) Union T fitting (Metric)
F) 2x hand-formable hard lines (Note: on both, one end is standard threads, opposite end is metric)

Step 1 is to remove your old master cylinder from the car. Follow these steps for removal:

- To avoid a mess, remove the fluid from the reservoir. A suction device or turkey baster works well. Then place towels or rags underneath the master cylinder to catch fluid that will drip when you remove the lines.
- Disconnect the brake line fittings from the master cylinder. Use a 10mm box wrench for these fittings as a normal open-ended wrench can round them off.
- Remove the two 12mm nuts that hold the master cylinder to the brake booster, and remove the master from the car.

Once removed you'll be left with this view:


Now moving away from the car for a bit - before installing your master cylinder, you must bench-bleed it.

Before we do that, a handy tip is to mark the hard brake lines included in the kit according to the threading on their fittings. Each of those lines has metric threads on one end, and standard threads on the other. To illustrate the point, I wrote this on the bits that we installed for this example (note that there are no markings on your kit)


The bottom ports in the wilwood master cylinder are standard threads, and both of the union fittings included in the kit are metric threads, so attempting to thread the ends of the hard lines into either of those ports will quickly reveal which end is which. Mark those ends with a small bit of tape (sharpie will rub off with brake fluid).

Now on to bench bleeding:

The kit includes two plastic fittings - install these in the bottom ports of the master cylinder. Note that the threads on these fittings are not exact matches to the master cylinder's, but they will thread in enough for one-time bleeding use. Screw them in until at least a few threads are engaged and the fit tightens up:


Place the master cylinder in a vice, and run the clear hose from each of the plastic fittings up and back into the reservoirs so that the fluid pushed out of the master is recirculated. We used some tape and a paper clip to make sure the lines didn't slip out during the process:


Fill the reservoirs with brake fluid to the full line.
Use a long screwdriver to depress the piston in the master cylinder and cycle the fluid out of the bottom ports:


On each repetition, press the piston all the way until it bottoms out. Each time, you'll see small bubbles exit the lower ports and travel a short distance through the tubing, eventually making their way back to the reservoir. Long, deliberate strokes are more effective than short quick ones. Repeat until there are no more air bubbles leaving the lower ports. This will take a LOT of repitition. We usually spend about half an hour on this. If in doubt, keep repeating.

Air bubbles in the lines:


Once there is no more air in the system, carefully move the master cylinder from the vice to the car. You'll keep everything assembled with the plastic fittings and hoses in place while you do this. Install the included adapter bracket on to the brake booster, and then attach the master cylinder to the bracket. The assembly will look like this:


One of the hard brake lines in the car has a banjo fitting on the end. Remove that fitting:


At this point you'll see that the fittings do not line up with the new port locations on the bottom of the master cylinder. Two hand-formable hard lines and the union fittings are included for this purpose.

A note on brake lines and teflon tape: many people struggle to get brake lines installed without leaks. There are several threaded junctions in the following process. We recommend standard teflon thread-sealing tape (available at any hardware store) on every threaded junction between a male and female line and fitting.

Your new master cylinder has two reservoirs. The reservoir and corresponding bottom port towards the front of the car is for the rear brakes. The line that you removed the banjo fitting from is your rear brake hard line. Install the straight union fitting from the kit to that line, and attach the metric side of the included new hard line to the union fitting. Then bend the hard line so that it lines up with the port on the underside of the master cylinder. You may need to adjust/bend the factory hard line as well to accomplish this.

On your new master cylinder, the reservoir and corresponding lower port that are towards the rear of the car are for the front brakes. There are two factory hard lines running to the master - one for the front brakes on each side of the car. Use the circular T fitting included in the kit to join each of those lines with the metric threaded side of the hand formable hard line from the kit. The T union is not directional, and all ports are female metric threads, so the orientation does not matter. Then form the hard line to line up with the rear-most bottom port on the master cylinder. Again, you'll need to do some bending of the factory hard lines as well to accomplish this.

Every car is a little different, with some components in the way, etc. so every install varies with how the hard lines are ran. Here is how we did it on Sean's car. Note that he has a proportioning valve in-line with the factory rear brake line, so the line passes through that valve and then goes to the union fitting from the kit and then to the front port on the master cylinder:


With the lines formed and installed, the last step is to remove the plastic fittings from the master cylinder and quickly install the new hard lines. Some fluid will be lost while you transfer between the two, but as long as you don't leak so much that the reservoir is emptied, the work done to remove the air from the master cylinder will not be lost.


With the lines properly installed in the master cylinder, top off the reservoirs if they have dropped below full, and then proceed to bleed the brake system in the standard manner at all four corners/calipers.

After bleeding the brakes, inspect each of the fitting junctions around the master cylinder for leaks. If a fitting is leaking, disconnect it and reapply teflon tape, then reinstall. Note that you will need to bleed the brakes again if you disconnect any lines.

With everything bled and no leaks present, you're ready to enjoy your new master cylinder! Do a test-run at low speed to ensure everything is working properly, and check for leaks again after a few miles.
Ryan @ GWR
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Joined: Fri Oct 17, 2014 11:37 pm

Re: Wilwood Brake Tandem Master Cylinder Install

Postby AlexD859 » Wed Aug 10, 2016 1:21 pm

Can this be installed on factory brakes? I am in the process of building and exocet, and would like to upgrade the factory brakes down the road, but would like to run a new master cylinder in the mean time. Thanks
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Joined: Thu Dec 26, 2013 1:58 am

Re: Wilwood Brake Tandem Master Cylinder Install

Postby Ryan @ GWR » Sun Aug 14, 2016 7:54 pm

Yes, result with the factory calipers on all four corners will be a stiffer pedal and it requires a bit more leg pressure to get the same braking torque as you'd get with the factory master cylinder. OK to do in a Miata if you prefer that stiffer pedal feel, but I suspect with the Exocet which is so light and thus doesn't need as much braking torque to make a stop, that might actually be an even better combo.
Ryan @ GWR
Posts: 396
Joined: Fri Oct 17, 2014 11:37 pm

Re: Wilwood Brake Tandem Master Cylinder Install

Postby AlexD859 » Wed Sep 07, 2016 5:31 pm

Thanks for the info, I have recently decided to go with a chase bays brake booster eliminator, with wilwood master cylinder.
Posts: 15
Joined: Thu Dec 26, 2013 1:58 am

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