# DIY: Changing Master Cylinder (brakes, WITHOUT ABS) mk3



## ADeHelian (Oct 1, 2009)

Okay so you're brake pedal goes to the floor, you push harder once your pedal is all the way down and the car eventually stops. You think there is air in the lines, so you bleed your brakes, but it doesn't work , well, your master cylinder might be leaking (it may be internal so you wont necessarily see it)

This DIY is how to replace a master cylinder on a Mk3 WITHOUT ABS, If your mk3 doesn't have ABS there is only one style master cylinder to use --->  german auto parts If your mk3 has ABS then there are multiple different types it may use. GAP carries every and all parts. I actually got mine out of a junkyard for 13 bucks 

OKay so. Stuff you'll need:








4 jack stands, jack, bottle of appropriate brake fluid, and canister to put used brake fluid in.








turkey baster (don't use your mothers, you can get one at the dollar store)








13mm and 11mm wrenches








some kind of wire brush for removing rust








box wrenches, or line wrenches, whatever you want to call them








and a piece of 1/4 inch fuel line got it at an auto parts store for 2 dollars








optional: torch

okay so you got all the goodies first step is get the car on the jack stands








make sure you put the jack stands on appropriate spots under the car, push down on back bumper to see if the car moves, if it moves at all you may want to rethink your jack stand placement. Car should be just as sturdy as it was on the ground.

next step is to identify the master cylinder, to do that you must first find your master cylinder reservoir.








the master cylinder is directly beneath that.








the metal piece with the brake lines going into it is the master cylinder. The reservoir is attached to the top of the MC by a clip on each side
Before removing the clips, get the turkey baster and suck out as much old brake fluid as you can from the reservoir. Then gently using a screw driver or fingers pry the clips off, making sure the clips are free pull up on the reservoir (with quite a bit of pressure, the MC is stuck on pretty good). Once you get it off just lay it off to the side out of the way. Now since there is not much room to work, I also unbolted my coolant reservoir and set that off to the side as well, that step is not necessary but I guarantee it will save time in the long run. It's just two bolts on the side and you can just set that off the the side as well.








So now you should see the MC with 4 brake lines attached and two cylinders in the top, suck out any fluid in those cylinders using the baster









The next step is removing the brake lines from the cylinder, this is where the line wrench or box wrench comes in handy, the line wrench grips at 5 places on the nut instead of the regular 2, this will prevent you from rounding off the nut. **always use a line wrench to loosen or tighten the brake line nuts**








now once you've broken it loose you can of course use the 11mm wrench to get it off the rest of the way. Once you got all 4 brake lines off the MC just set them aside, try not to bend them too much.
Next step is removing the two nuts that hold the MC on. This is where the torch may come in handy depending on the amount of rust present. Using the 13mm wrench remove those two nuts. (this may take what seems like forever because of rust deposits.








The master cylinder should just pop right off when those bolts are loosened, if for some reason it does not, a few light taps from a rubber/plastic mallet will do the trick.

Now the next step is very important in saving you about 10-15 minutes. Get the wire brush and some WD-40. Spray the WD on the MC mounting studs and wire brush off as much rust as possible, this will enable you to simply hand tighten the nuts back on. 

Lastly you get your "new" master cylinder and if you got the correct one it'll just slip right into the position of where the old one was. Tighten down the two nuts to attach the MC to the brake booster, and then put in all 4 brakes lines and tighten them as well, remember you can start tightening with an 11mm but only torque it down with the line wrench. If your line wrench set is standard size use the 9/16th. After all nuts are tight, place the reservoir back on, attach the clips, if you took off the coolant tank or any other accessories, place those back on too. Then fill the MC reservoir to the tippy top.

Still not done  now that you took the MC off you might have heard a hissing noise coming from the mounting point of the MC thats because you just let a whole bunch of air into your break system. Now you gotta get that out. Luckily your car is in the air so this will just take about a half hour. If you haven't already, take off all 4 wheels. Air gun would be helpful, but a lug wrench works just as good 

Bleeding brakes: you're going to need a helper who is very good with instructions.

Now when you bleed your brakes you want to start with the bleeder farthest away from the MC so that would be the right rear bleeder valve, then the left rear, front right, front left.
Bleeder valves have little dust boots on them.








Remove the dust boot, place your 11mm wrench over the bleeder valve nut and then attach the line to the valve, place the other end of the line into a clear bottle filled with about 1/2 inch of clean brake fluid. 









***Now it gets tricky, any mishaps or miscommunication here can cause air to get in your lines, if that happens at any point, you must start over. That being said:

-Cue your helper to pump the brakes 3 times and on the third time hold down firmly. 
-When your helper has the pedal down he or she should say "down" 
-Then when you know the pedal is being held down, you open the valve. (Let your helper know that each time you open the valve the pedal will sink, make sure they apply even pressure all the way down.) 
-Air should flow out of the valve, when no more air comes out close the valve and say "pump" 
-Your partner will pump and hold down again.
***periodically check the MC reservoir, you will need to keep adding brake fluid after every couple open and closes of the valve. If at any time the reservoir dries up, that means you were sucking in air, and you must start over.***
-You and your helper will repeat these steps on each valve until little to no air comes out. 

When no more air comes out of the front left brake line, put your wheels back on, clean up, and take the car for a test ride. Generally when test riding a car after fixing brake components you don't want to drive on a road right away, just test the brakes in your driveway, if you're comfortable with that, then take it on the road for a test.

I hope this helps someone, I feel I put too much detail in it, but better more detail then not enough so yeah, and I tried to use grammar correctly, but I'm not perfect.


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## Mr.loops (May 27, 2010)

Nice write up!


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## ADeHelian (Oct 1, 2009)

Mr.loops said:


> Nice write up!


thanks man, it's my first one :thumbup:


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## tkcamper (Mar 16, 2011)

*Thanks!*

Gonna do mine this week. This is a huge help.


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## ADeHelian (Oct 1, 2009)

tkcamper said:


> Gonna do mine this week. This is a huge help.


if you got any questions shoot me a pm.


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## Mr.loops (May 27, 2010)

Did you not have to bench bleed the M/C before intalling it?


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## ADeHelian (Oct 1, 2009)

Mr.loops said:


> Did you not have to bench bleed the M/C before intalling it?


I bled the whole system after I installed it. You could bench bleed it, but your still going to end up getting some air in the system and have to bleed the whole system anyway.

the bench bleeding method is annoying IMO


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## golfprint (Apr 1, 2011)

*Brakes G60 1990 corrado abs*

Would this be the same procedure with an abs brake system? I need to replace my Hydro unit and ABS control unit. Thanks keith


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## ADeHelian (Oct 1, 2009)

golfprint said:


> Would this be the same procedure with an abs brake system? I need to replace my Hydro unit and ABS control unit. Thanks keith


When you change the hydro unit and the abs unit make sure you 1. depressurize the system and 2. never turn the ignition on unless all the sensors and stuff are hooked back up the the abs unit.

for the rear bleeding procedure the accumulator pressure is used to assist in the bleeding so you gotta be careful. The pressure is like 3,000 psi.

1. okay so to bleed the rear you hook up the hose to the bleeder screw like you would with the front but before you do anything locate the height sensing proportioning valve. (this is the regulator that senses your ride height and adjusts brake fluid pressure to the rear brakes.) 

2. position the actuator lever on the regulator towards the rear of the car. 

3. depress the brake pedal and turn the ignition on. 

4. Have your helper open the bleeder screw and the fluid will flow out. keep it open until no air is present in the lines. Do the same for the other side. never let the pump run for more then 2 mins at a time and keep checking the reservoir.) 

5. once the rears are done depressurize the system and do the front. The front are done the normal way like i described in my original post.

hope that helped :thumbup:


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## golfprint (Apr 1, 2011)

*Brakes*

Thanks for the information. But how do you depressurize the system sorry I'm a newbie. Keith


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## ADeHelian (Oct 1, 2009)

golfprint said:


> Thanks for the information. But how do you depressurize the system sorry I'm a newbie. Keith


its all good, to depressurize the system you simply make sure the ignition is off and pump the brake pedal 25-35 times. thats it!


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## procket2_8 (Feb 19, 2004)

can anyone tell me what brake line goes to what port on the non abs master? I swapped a non abs master in my mk2 and the front brake lines were installed on the left side of the master(looking at the front of the car) and the rears on the right side ports. Its the 22mm master but my brakes suck.

I have the twin piston Girlings up front and regular rears. I am redoing all the brake lines and I got to thinking and wondering if the lines were actually wrong?

Any help would be greatly appreciated.


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## ADeHelian (Oct 1, 2009)

procket2_8 said:


> can anyone tell me what brake line goes to what port on the non abs master? I swapped a non abs master in my mk2 and the front brake lines were installed on the left side of the master(looking at the front of the car) and the rears on the right side ports. Its the 22mm master but my brakes suck.
> 
> I have the twin piston Girlings up front and regular rears. I am redoing all the brake lines and I got to thinking and wondering if the lines were actually wrong?
> 
> Any help would be greatly appreciated.


i will post a picture later on tonight to show you if there is any confusion but if you are looking into the engine bay at the master the closest port to you on the right is the Front Left. the second one (more towards the booster) is the Rear Left. Now the left ports the first one (closest to you) is the Right rear and that leaves the booster side port on the left side to be the Front right.

like i said if that was too confusing i will post a picture shortly.


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## procket2_8 (Feb 19, 2004)

thanks dude I appreciate it. I was wondering why my brakes sucked and I am sure that the kid I got the car from had them in the wrong port....not sure that that matters but...you never stop to really think which one goes in which port lol


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## ADeHelian (Oct 1, 2009)

procket2_8 said:


> I was wondering why my brakes sucked and I am sure that the kid I got the car from had them in the wrong port....not sure that that matters but...


it does matter. ill explain why.

first things first. heres the correct setup 









now the reason they have to be setup like this is because our car (and most cars for that matter) are setup with a criss cross braking setup. The master cylinder has a pushrod inside. And without going into too much detail, when you hit the brake the push rod forces the hydraulic fluid through the master cylinder and the first two lines that get brake pressure are the front right and rear left. so the criss cross braking helps stabilize the car under braking. then as you push the brake more the other two wheels get brake pressure. so the car should always be getting an even braking in the left wheels and right wheels. 

another acceptable setup is a front/rear setup where the front wheels brake first then the rears. while this setup is acceptable the better setup is the criss cross. 

now the setup you had doesnt work because one side of your car (lets say the left side) would brake first then the rights. so under initial braking the car would be very unstable. also if the guy didnt know what correct ports to connect the brake lines to, he probably didnt know how to properly bleed the brake system which would also make your brakes 'suck'

hope this helps.


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## procket2_8 (Feb 19, 2004)

That picture is great thank you!

Well I started by replacing the calipers, put the dual piston grilling ones up front and re bled the car....still the brakes were terrible. I couldn't even lock them up. Next I put new pads and replaced the master cylinder still...brakes were no good. So when I stripped the car down to work on the motor and clean up the firewall I removed all the brake lines and things and thought....I don't even know if these are correct.

Thats when I though.. I am not even sure how they should be lol. Then I found your post and was thinking maybe someone knew...

Thanks a lot for your help! Hopefully when I put this pig back together it will be a lot better!


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## ADeHelian (Oct 1, 2009)

gooluck :thumbup:


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## tomjv (Jun 15, 2001)

*Nice writeup*

Two things:
1. quote>"Still not done now that you took the MC off you might have heard a hissing noise coming from the mounting point of the MC thats because you just let a whole bunch of air into your break system."
That hissing is the air coming OUT of your brake booster, not air going IN.

2. what about bench bleeding?
TomJV


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## xon_88 (Jan 21, 2013)

*nice walkthrough*

Thanks man. Master cylinder on my 1994 Golf MK3 RHD (non-ABS) was leaking into the servo (brake booster) and managed to change it yesterday thanks to this walkthrough. We found the servo brim-full with fluid which I managed to suck out with a syringe connected to a clear pipe.

When it came to fitting the reservoir into the new MC however, we didn't manage (put all our force into it for nothing), so we used the rubber seals from the old MC instead. Also used the 2 blanking screws from the old MC as the new one came without them (I only have 2 brake lines connected to the MC).

Bleeding the lines was quite easy with the help of a friend - I don't think it's worth the hassle to bench bleed the MC. Started from the furthest wheel (which took the longest as it had most air and old liquid) and moved to the closest to the MC. also replaced DOT3 with DOT4 fluid.

FYI:
1. for the rear wheel hubs, the bleeder nut was 7mm - therefore you might also need this spanner.
2. take pictures before removing anything, so you can refer to them when replacing (for ex. reservoir and brake lines positioning).
3. be sure to replace the seal between the MC and servo (does not always come with the new MC).
4. don't get any brake fluid on your paintwork.


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