Check yourself, before you brake yourself. That’s not a clutché.

posted in: DIY | 0

Swapping s54 into e28 is like putting m50/2/4 but with some extra flavor. Bitterness comes first, before the N/A 342 hp sweetness. One of the challenges were to move from vacuum servo to hydraulic one out of m30 powered e28 so i could stick the s54 plenum in the bay without cutting or modifying anything and here goes the story ..

My car went for some maintenance after broken cv joint that almost ruined a weekend at the seaside.

Then i noticed few drops of brake fluid on my brand new floor mats, then some atf drops underneath  the hood  and everything ended with differential replacement since i hit upon S3.25 out of parted out car (S2.65 previous) , changing bunch of hydraulic hoses 2 months right after Stan saved my ass on my wedding day, but that’s a different story.


All was set, I had some issues with the brake bomb ( brakes was hard when you hit them fast and soften up after a second – a clear symptom of shot unit), after replacing it with brand new everything worked as a charm, but one day I’ve found an empty canister and huge stain under the car. The bottom side of the servo was all in atf oil – no wonder after 30+ years of service. I had to do it before installing it on the car for the first time, but apparently it was about damn time to make that DIY for that repair kit we’re selling over 6 months already.. so no regrets.

My everyday life as e28 enthusiast actually reminds me of a certain Malcolm in the Middle scene..


This article is written, so it can help by showing steps and methods to anyone who decided to rebuild his/her e28 hydrobooster and master clutch cylinder. If you’re not completely sure about your mechanical skills or/and knowledge, please find a professional mechanic or authorised shop to do the job for you.We at are not responsible for any harm, injuries or material damages that may occur by using e28goodies “the everything” hydrobooster kit / MCC kit caused by incorrect installation of the components or misunderstanding of our “Do It Yourself” guide . You’re at your own risk, so you are responsible for any harm or damage that you or your car might suffer as a result.
If you agree with the stated above, please keep reading this article. 


So what you’ll need for the job:
e28goodies “the everything” hydrobooster repair kit.
– 11 mm flare nut wrench
– 13 and 17 mm wrenches
– 1/4 ratchet with extension with 10 & 13 mm sockets
– 1/2 ratchet extension with 32 mm socket
– side cutters
– vice grips
– flat screwdriver
– phillips screwdriver
– hammer
– atf oil
– brake cleaner
– rag
– protective glasses

Super easy and fast.

The Rebuild.

So here is what i got on the table.

Common issue is shaft play into the seal. That get you the leak in most cases.

Be adviced – super compressed spring into the hydrobooster body. It might blew your head off. Put some protective glasses on and install the e28goodies compression tool. Adjust it as shown on the picture and then proceed to the removal of the knurled bolt.


Untight the nuts (a bit slow than removing the whole bolts, but better safe than sorry )

Now you should be able to see a portion of the internal parts.

Now let’s get with the pedal side of the booster. Measure the distance between the nut and the little duct that goes around the shaft (just at the end of the thread) and write it down. When you put everything back together , you’ll need to set that to initial position . If not your brakes might be engaged even with your foot off the pedal (too tight) OR some dead play of the pedal before it actually start engaging the brakes ( too loose)

Remove the locking nut and the shackle.

As well as the oil felt washer.

Now you should be able to see this :

Push the rod. Might be a bit though.

The rest of the components should came off on the other side. Pull the piston out.

If the o-rings are super worn out, the piston components might pop out without any force applied. The piston contains small spring in the bottom.

If it’s out – put it back !

Small sealing insert

and a tiny spile.

This is a schematic of the whole unit disassembled. The wider side of the larger spring should face the master cylinder pump side, and the narrower part should land on the washer that seats inside of the piston.

Now, lets get with the piston. Take off the rubber o-rings that stays behind the teflon o-rings on both sides.

Install the new ones that are in the kit. They’re same size.

The new teflon rings are tight and since they don’t have any stretching properties, it might be a little bit tricky to get them in place. Be smart and dip them in something which is their natural habitat – ATF oil.

You can help yourself with tiny flat screw driver to get them over the edges. Be gentle.

Replace the insert’s and the spile’s o-rings.

On the back side (pedal side) of the booster, you will notice the push rod is going right through a o-ring and a plastic washer. Make sure you’re changing them too or someday you might wake up with an ATF leak in the footwell.

Take the old ones out.

Original plastic washer got that slit.

Grab your cutters and cut your new one.

Install the new o-ring. Again a flat screwdriver might come handy.

And then install your new washer just as shown.

Everything should look nice and even.

Peel off your old gasket (and don’t forget to install the new one while you’re getting the booster back to the car).

While everything is out, you might want to spray the microfilter mesh basket (and the whole hydrobooster body – in and out ) with a brake cleaner.
It will shine on as new.

Before putting everything back together, make sure you have the tiny spring in place in the piston. It should make that “click” noise and shouldn’t come off easily. Just turn the piston down, shake it and if the spring doesn’t fell off – you most likely did it right.

First goes the insert .

Then goes the cap.

Place the piston back in the booster body, making sure the rod is going through the hole on the back side. Lube components with  ATF oil.

Use 32mm socket, ratchet extension and a hammer, to press it gently by tapping it into place. Tap it all the way down till the end.

Now take the oem push rod, o-ring, washer and plastic cap … and throw them in the trash. You will use the e28goodies parts and install them as shown.

Compress the spring by hand a bit and install the piston compression tool.

Now this is the most annoying part of the job since the nuts need to be tighten equall – alternating 3  x 360 degree turns.

When the bottom hole of the  cap matches the threaded opening on the booster body, put on the new bolt. It’s not knurled anymore, we’ve made standart 10mm bolt to match the booster specifications. So tight it up with 10mm socket/wrench.

You’re done.

If you observe any mechanical damages over piston or body contacting surfaces do not proceed with the rebuild of this unit. Try to find another one in better condition and start all over again with it. Pictures below are representing some serious damages, it’s actually the unit of my car, but im glad i had another one to rebuild and use. This ain’t joke, it’s serious thing  so be aware.

Now since you’ve got your booster down, you might wanna check your master clutch cylinder (1). Mine was leaking so I’ve used the e28goodies MCC repair kit to rebuild it. The master cylinder is held to the pedal bracket with 2 x m6 bolts (10mm head) (2) , also 1 bolt that fixes it to the clutch pedal  (17mm head) (4),  13mm nut (5) and 11 mm flare nut on the back side (11)  that holds the hardline going to the slave clutch cylinder. Make sure you’ve pulled out the feed hose that comes from the expansion tank first (9) and then pull out the nipple out of the master clutch cylinder (7)



Tools :
e28goodies MCC repair kit.
– 11 mm flare nut wrench
– 17 mm wrench
– 1/4 ratchet with extension, 9,10 & 13 mm sockets
– flat screwdriver
– pliers
– brake fluid
– brake cleaner
– rag

Rebuild process.
As i said above, I had minor leak of few drops per day right on my brand new floor mats.Turns out the master slave cylinder had some worn out seals that caused  leakage through that tiny hole on the dust cover.

Since the e28goodies MCC kit contains brand new rubber boot, I suggest to rip off the old one (if it’s not already like this one).

Remove the circlip.

And the C-shaped washer underneath.

Use a screwdriver as a handle and pull out the piston.

This is what you should see so far.

Now comes the spring. Narrower part faces the piston. Wider goes inside the master clutch cylinder body (hardline side)

Remove the feed line grommet by helping yourself with a flat screwdriver.

A schematic of the order of all internal components of the MCC.

Now, using the pliers pull out the tooth lock

Then pull out the bottom seal (be advised, seals are different so mind them.)

Pull again the rod, so it will come off the piston (ball socket).

Remove the top seal (Once again – both seals are different. Pay attention)

Clean everything with a brake cleaner and a rag, including the inside of the master clutch cylinder.

The trickiest part here is how to install the new top seal. Well, just lube everything with brake fluid use a flat screwdriver to get it done.

Put the bottom seal and using socket 9 and extension, hammer in the tooth lock washer.

Install the new dust cover on the rod.

Install the new feed line grommet.

You can try to overcome the edge by pushing hard the grommet down or using a screwdriver.

Put the spring back in. Narrower part to the top !

Push the piston in.

Put back the c-shaped washer.

And the circlip.

And snap the dust cover down.

You’re good to go for another 15 years.

Be advised.
After rebuilding and reinstalling your hydrobooster, master clutch cylinder or both – you’ll need to bleed them.

Bleeding the systems for dummies. 

How to bleed the brakes:
1. Fill the brake fluid reservoir to the top.
2. Get someone to pump the brake pedal for you.
3. Go to the farthest wheel from the master brake cylinder (on lhd car that is right rear wheel)
4. Ask your helper to start pumping the pedal. On each 3 pumps he/she have to hold the pedal pressed. Meanwhile you need to unscrew the bleeder cap of the caliper. Braking fluid mixed with air bubbles will start comming off. Do it until bubbles aren’t appearing anymore. Repeat untill you do all four wheels. During procedure constantly look at the reservoir  to make sure you have enough fluid there.
(LHD order of the wheels – 1. Rear right 2. Rear left 3. Front right 4. Frong left)

How to bleed the clutch.
1. Fill the brake fluid reservoir to the top.
2. Get someone to pump the clutch pedal for you.
3. Locate the bleeder on slave clutch cylinder underneath the car (left side of the gearbox)
4. Ask your helper to start pumping the pedal. On each 3 pumps he/she have to hold the pedal pressed. Meanwhile you need to unscrew the bleeder cap slave clutch cylinder. Braking fluid mixed with air bubbles will start comming off. Do it until bubbles aren’t appearing anymore. During procedure constantly look at the reservoir  to make sure you have enough fluid there.

How to bleed the hydrobooster (and the power steering).
1. Locate the powersteering tank and fill it. ( Don’t overfill it. Fluid should be about 3 cms under the filter mesh)
2. Start the car.
3. Check the ATF level. Fill some extra if needed. ( Don’t overfill it. Fluid should be about 3 cms under the filter mesh)
4. Start spinning the steering wheel from the left full lock to the right full lock about 15 times.
5. Check the ATF level. Fill some extra if needed. ( Don’t overfill it. Fluid should be about 3 cms under the filter mesh)
6. Press brake pedal about 50 times.
7. Check the ATF level. Fill some extra if needed. ( Don’t overfill it. Fluid should be about 3 cms under the filter mesh)

PS. Just for curiosity´s sake !!!