Fitting E32 Master Cylinder

If you've recently upgraded your brakes by fitting some E34 calipers, then you'll need a bigger master cylinder to push all that extra fluid around.

Here's how to install the Master Cylinder and servo from the mighty E32 7-series.

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Parts

• E32 735i Servo, Master Cylinder and Reservoir

Tools

• 3/8 socket set
• 11mm brake pipe spanner or combination if you don’t have one
• Screwdrivers
• Electric drill and bits up to 12mm
• Carbide burrs
• Grinder and discs
• Tap and die set (M10x1.5)
• Cutting oil (wd40)
• Rags for keeping stuff clean
• Some washers

Procedure

Open the bonnet and undo the air intake boot by loosening the two jubilee clips and the ICV

Looking at the rear of the engine bay on UK nearside to see the servo setup

Undo the two brake pipes coming out of the MC with your 11mm spanner. Catch any fluid in a rag or bucket as fluid will pour out the MC and pipes

Remove the MC from the servo by undoing the two 13mm nuts (some people may not need to remove this from servo but I found with the space left by the M20 it looked easier)

Inside the car slide the passenger seat all the way back or remove completely if you want even more space (4x17mm)

Remove glove box using the two screws mounted to the bulkhead. Be prepared to find signs of Rust in your bulkhead.

You will now see the brake clevis and mechanism to turn the movement through 90 degrees.

Take the pin out of the clevis by removing the clip, but keep your hand round it as it will want to fire

off somewhere and not want to be found, the slide the pin out and keep it all safe

Following the push rod towards the bulkhead you will see a big black plate with 4 13mm nuts

Back to engine bay side and pull servo free from bulkhead and remove from the bay

Admire your gaping hole and repair any rust while this is out

Get the E32 servo and remove the spacer as this hinders clearance with the M20 intake boot

You’ll now see that there are only two studs to mount to the bulkhead, this is fine and it’s not exactly heavy

These two studs don’t fit in the standard holes so you can either drill some new ones a bit further

over or open up the holes already there, I voted for the later

Using a carbide burr I slotted the holes roughly 8mm towards the center

Test fit number one to see if it clears... IT DOES!

Look inside at where it bolts and you’ll see that the push rod is far too long and needs shortening a

lot

Remove the servo again and look at the rod, its a lot fatter than the thread so needs grinding down

so the die wont get stuck and snap something

30 seconds with a grinder and the shaft was small enough to work with

Wound on the die and sprayed loads of wd40 at the teeth as I started to make the new thread

I wont go into technique but If you’ve never tapped anything before then your best learning before

doing this as if you get it wrong it means buying a new servo

Thread it as far as you can, I held the rod in a pair of mole grips I clamped into a vice to stop the

shaft spinning and not cutting

Once its threaded its time to take it back to the car to see how much it needs shortening

Test fit number two

Attach your clevis to the mech and then place next to the noe fully threaded rod

This will tell you how much to take off, best to take too little than too much as you can always take a

little more bit by bit

Make sure your die is wound on past where your cutting before you cut it, this allows you to clean

the start of the thread after cutting it

Cut it off and then wind the die off

The clevis should now thread nicely onto the shortened rod

Take back to the car and fit again for third time 

If all is well you wont need to remove again so add a washer and bolt the servo to the bulkhead

The clevis can be adjusted to suit the brake mech and can also be adjusted to take any slack out of it

Leave the glovebox out for now until its all done as you may need to adjust little bits

Grab your new matching MC

Bench bleed it by filling the resivoiur of suitable dot rated fluid

Keeping the holes plugged with rags or your fingers install the MC to the servo and quickly put the

brake hard lines In, you will need to bend them to fit as the MC is now further away from the

bulkhead but its not hard or too far to bend them (if your really anal then make new ones but im on

a budget)

Bleed all the brakes starting from the furthest away from MC so OSR NSR OSF NSF

Test drive time

If any slack in the pedal then the clevis/brake rod can be adjusted

Once all is well and no leaks have appeared then install your glovebox and hopefully you’ll have

more braking assistace to match any caliper upgrade you’ve done.

With the E34 calipers on the front, and potentially bigger brakes on the rear as well, the standard E30 master cylinder isn't big enough to move enough fluid. To get around this, most people use the E32 750i MC but I also wanted more assistance to match. The 750i MC is also becoming increasingly expensive due to its rareity, so I'm opting to use a more mundane E32 735i MC and servo instead. This master cylinder is still 25mm, so should improve the feeling to near stock level

However, a few mods will be needed to make this fit.

The E32 I got mine from had a spacer on the back of the servo. There are two options here:

1. Use the spacer. This requires the least mods but the brake fluid reservior will be right underneath the inlet boot on the M20 engine, and might not fit.
2. Ditch the spacer, but make a few mods instead. This involves:

Grinding down and shortening the push rod to put the clevis at its original level Open up 2 holes in the bulkhead Bend the brake lines slightly

I choose number 2 for an original look to the engine bay

Start by opening up the mounting holes E34Brakes005

Grind down the pushrod E34Brakes006

Start making the thread using your die E34Brakes007

Cut about an inch and half cut off (37mm), and thread it as far as you dare E34Brakes008

Remember if you're doing this yourself then leave the die wound on before you cut the excess off. That way, you can then unwind it and clean the threads so that the clevis can go on with no trouble

test fit E34Brakes009

I was made up that the standard E32 vacuum line was in the perfect place to line up to the E30 system

The clevis is the trickiest part I lost the E30 clevis so I used the E32 one but it was way too long. This required trimming and slight mods so please keep your E30 one unless you want some trial and error fitment issues that involves installing and removing the servo/clevis multiple times E34Brakes010

All done apart from take it all apart to paint the servo and bench bleed the MC E34Brakes011