How To: Swap your Brake Master Cylinder and brake booster


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This writeup, along with others is permanently hosted on my website:

How to Swap your Brake Master Cylinder and brake booster

Swapping the Brake master cylinder:

Open the resevoir cap and remove the fluid from the resevoir. a syringe works if you have one.
Remove the two brake hardlines that run from the master cylinder to the prop valve. you can simply remove the mc side

since i was upgrading to a new Master cylinder that requires new lines i fully removed the stock mc to prop valve lines.

Disconnect the resevoir cap wires

remove the two 12mm nuts securing the MC to the booster and remove

comparing some master cylinders.

at this point if you are ONLY replacing or upgrading the master cylinder, skip down past the booster swap steps. If you are also replacing or upgrading your booster, continue below.

Swapping the Brake booster:

Now we climb under the car and locate the 4 12mm nuts and the pin and cotter clip. remove all

here's a view of the pin and the cotter clip

All the hardware removed

remove the brake booster vacuum line from the front of the booster

Now remove the booster from the engine bay. you may find you have to unbolt the bracket that holds the throttle cable and clutch slave line. You can see it unbolted and moved aside.

comparing some brake boosters.

make sure you install the gasket on the back of the brake booster where it mounts to the firewall.

Now if you are installing a much larger booster, like i am with the teg abs booster. you may find some difficulties squeezing it in. i actually had to take an angle grinder and cut a small tab off my y8 IM.
the IM before

the IM after

You might also find it benicial to unbolt the bracket that holds the clutch slave softline the firewall. this gives you more play on the hardine.
Finally, got the new huge booster fitted into the firewall.

Now go back inside the car under the dash and reinstall the 12mm nuts(torque to spec) and the pin and cotter pin. Here's a picture lining up the booster arm with the brake pedal.

Now reconnect the brake booster vacuum line. You can also reconnect the clutch slave cylinder line brackets if you unbolted them earlier.

If you have to make new lines like i did read here. if not skip over the making new lines part

Making new MC-prop hard brake lines

Here's what you need. you need youre stock MC to prop valve lines. a brake line bender tool and some new brake hard lines. The brake hardlines come preflared with the fittings already on the line. All you have to do is measure the lengths of your old ones and get the closest line longer than that. Don't want to get one too short. Now on this particular MC (1" 94-97 integra abs) has two different sized ports. so i had to get a line that had both smaller sized port, cut off one end, put the new bigger fitting on and then reflare the end.

temporarily mount the master cylinder to the booster so you can mock up your new lines.

Now start bending your lines. i started with the easier shorter line. I removed the vac booster line for clarity.

Both new lines made

Installing the master cylinder.

It is important to bench bleed the cylinder first. Install bleed lines (u can make your own) that feed right back into the resevoir. fill the resevoir with new dot3 brake fluid then manually press in the master cylinder piston, you'll watch air and some fluid push through the lines and into the resevoir. It is important to have the lines in the fluid so that as you release the piston back out it draws in brake fluid and not air. It takes roughly 10 pumps to bench bleed the MC. do it slowly and carefully and until you see no more bubble in the lines or resevoir.

When installing the MC back onto the booster, make sure you have the seal shown here

now install the MC to the booster(torque to spec) with the bleed lines STILL attached. this way you can disconnect them one at a time and quickyl install your brake hard lines, minimizing fluid loss. Torque the lines to 6.5ftlbs

Now reconnect the wires on the resevoir cap, top off the fluid,rest the cap ontop and your ready to bleed the brakes.

Both Haynes and Helms state the brake bleeding order for 96-00 civic as:
1. Right Rear
1. Left Front
1. Left Rear
1. Right Front

congrats you have successfully replaced your brake master cylinder and booster. You can now enjoy pushing more fluid to those big brakes :-)



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You rule Luke! That was a great write up.


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I had to do this on my old 94 s-10 blazer. Not fun, lol Great write-up though, very detailed and helpful.


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I had to do this on my old 94 s-10 blazer. Not fun, lol Great write-up though, very detailed and helpful.
well, the reason i asked is cause i'm gonna have to do this sometime this week, hopefully today. anyway, my nearest ecology/pick your part is pretty short on civics. i saw one ef civic std and a few couple of crx's and a few eg civics. if i change out my booster for one of a crx or an eg, do i also have to replace the master cylinder?


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i'm doing this on my civic EF/ED right now and i'm having a lot of difficulty removing the 12mm nuts. the only tools i have are 3/8 ratchet with a 12mm deep well, a 12mm reg, and a 3" extension. so far i've only removed the lower right nut and loosened the lower left one. i can't find an easy comfortable way to reach these nuts. does anyone have any tips or advice on how to do this? what tools do i need besides the ones i have?


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thanks for this post and pictures, replacing my booster today and this walked me through it, thanks again


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doing the booster today and the plunger is jammed in the booster, i bought this car used and i have no clue what they have done to it... can someone please help asap


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Cheeseboiger use a wrench and if u want comfy take out the driver's seat so you can lay on ur back n look up =)

Can I use the booster an MC from my prelude and put it on my civic? 92 lude - 95 civic


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still working on my honda, i was working on the breaks today.... ive bled the system, even bled the master, ive chanced the wheel cylinders. im getting really soft brakes on engine start-up.... what could it be a master cylinder leak? booster issue? air bubbles? some tips would be absolutely wonderful atm