Integra Brake Booster / Master Cylinder Upgrade

The last step in completing my brake upgrade after installing the integra rear disc swap, and front calipers is the brake booster, master cylinder, and 4040 Prop valve.

A issue I ran into after installing just the integra rear disc swap, and front calipers was that I had very low brake pressure, and the pedal would sink almost all the way to the floor before engaging the brakes. This was due to still using the stock civic booster and master cylinder. The civic’s are significantly smaller and can’t provide adequate pressure for the integra brakes. Here’s a comparison photo showing the size difference in just the boosters:

Here is a photo of the stock civic booster / master cylinder before I removed it:


Stock master cylinder removed, looks like it had a little leak and some rust from it.



Stock 30/30 Prop Valve removed.


Removed the rear master cylinder brake line, cut off the end to install the bigger 12mm nut required for the rear line on the master cylinder.



Using a flaring tool to re-flare the line after the new 12mm nut was installed.


Flaring success!


Had to bend the line multiple times taking it in and out of the engine bay in order to not bend it too sharp and avoid it rubbing against the shock tower, you can see here I was able to get just enough clearance.


New 4040 Prop Valve installed, mounting bracket isn’t compatible with civic line placement because it comes from a DA, so it is left just to float, but its very solid and the mounted brake lines prevent it from moving much at all.

Completed Integra Booster / Master Cylinder / Prop valve install! The difference is beyond night and day after doing two rounds of bleeding. The braking now engages almost immediately and has over double the brake pedal pressure (IMO) compared to the stock set up. The car will stop super quick and lock up the brakes now, This thing is ready for some track duty!


Final List of all parts to make this work:

  • 94 Integra LS complete front knuckle assemblies w/brake calipers and rotors
  • 97 Integra LS complete rear disc brake trailing arms and E-brake cables
  • 94 Integra LS ABS Brake Booster (290v)
  • 92-93 Integra 1” ABS Brake Master Cylinder (Adler)
  • 93 Integra 4040 Prop Valve
  • 93 Integra 12mm tube nut for rear M/C hardline


One Reply to “Integra Brake Booster / Master Cylinder Upgrade”

  1. Well done mechanics considering the lack of a properly mounted bench vice and brake line bending tube machine. And kudos to whoever figured out how to keep the spring loaded prop valve held closed while swapping it out!

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