# Mk3 Golf-Rear disc swap issues



## shwathebuck (Oct 5, 2008)

SO i swapped rear discs onto my mk3 yesterday and now i dont have any brake pressure,
I have to PUMP my brakes to get them working. 
-I swapped everything down to the rear hardlines for rear disc cars.
Only thing i didnt swap was the rear proportioning valve

Now ive read you can adjust the valve?
I read in a writeup about positioning the rear actuator on the proportioning valve?
but it was about changing the brake master and wasnt too specific

Does anyone know where it needs to be pointing in order to get proper brake pressure to the rear calipers
cause right now i have to pump it up to get them anywhere. the pedal just hits the floor.

I know the calipers are working correctly, i got them completely rebuilt from work and everything else is brand new.
i had it checked out at the shop next door to my work today and they pinched off the rear lines and said the pedal got rock hard. so im thinking it is the proportioning valve.

Any help is much appreciated.


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## germancarnut51 (Mar 23, 2008)

After you replaced the rear brake calipers, did you bleed the entire brake system (front and rear), or just the rear, and did the master cylinder go dry at any time?

Did you work the parking brake to adjust the rear brake pad clearance after you installed the new rear calipers and brake pads?

How did you raise the rear of the car to install the rear disc brake parts? Did you have the jackstands under the rear axle beam while you were bleeding the brakes, or was the rear of the car back on the ground, or did you have the lever arm on the proportioning valve tied up in the position it would be in when the rear wheels are on the ground?

The reason that I asked these questions is because the rear brake pad clearance must be adjusted by working the parking brake, because none of the brakes on the car will work correctly if the rear brake pad clearances are not adjusted properly.


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## shwathebuck (Oct 5, 2008)

The only time i had the rear beam in its normal position was when i installed the shims, and that was to make sure they went in the right direction when the car was on the ground because of the rear beam rotating when its lowered.

when i was done with the swap, i installed my ebrake cables and only bled the rear while it was in the air, i didnt touch the fronts

The guys at the shop next to my work also had it in the air yesterday and only bled the rear, but didnt get any results better than mine, but when the rear lines were pinched off, pressure got solid to the fronts, so im thinking it has something to do with the proportioning valve.

Where does the lever on the prop valve need to be pointing to get sufficient pressure to stop?
what adjustment can i make to fix it? if i have to, ill pick one up from a rear disc car and try it out, but id rather not have to

I know the rear pads are seating on the rotor, ive been using my ebrake to help me stop, and when i pump the brakes and pull the ebrake a little bit, it stops great. I just want to be able to fix this when i get home from work today.


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## greyhare (Dec 24, 2003)

The rear soft lines are downstream of the proportioning valve.

By your description the brakes are full of air. bleed all corners with the rear of the car on the ground. With the rear in the air there is very little pressure to the rear brakes and they will not bleed properly.


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## shwathebuck (Oct 5, 2008)

Just finished bleeding the brakes again with the rear on ramps so i could get under it, also adjusted the proportion valve up a little bit towards the underside of the car and still no brakes.
SO tomorrow im picking up a Master cylinder at work and hopefully it should solve this issue.
If not, where should i go from there?

Thanks for your help


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## germancarnut51 (Mar 23, 2008)

If the rear brake shoe clearance is correct, and the parking brake cables are adjusted correctly both rear brake should drag heavy at three clicks, and be completely locked up by five clicks.

If the parking brake cables are adjusted correctly, then the brake pad clearance is still too wide, and the brakes are not going to work correctly.

So, are the parking brakes locked up at five clicks?


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## shwathebuck (Oct 5, 2008)

The parking brake gets solid at three clicks and after five clicks the car wont move. i know the pad clearance is fine, even after the shims i put it, and i get brakes after a few pumps, but even after bleeding it twice myself, on all 4 corners, checking fluid level regularly, and even having it looked at by several guys with 30+ years in the automotive industry it still hits the floor. im thinking i may have pushed the master cylinder past its limits while i was bleeding, or it was already on its way out and the rear disc swap just pushed it over the edge. so im swapping in a new master tomorrow and hopefully all goes well. 

Does anyone know if its really necessary to bench bleed the master before hand? or should i be fine just throwing it in and bleeding all 4 corners again?

Thanks again for your help


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## germancarnut51 (Mar 23, 2008)

I don't bench bleed, but I don't pump the brake pedal to bleed the brakes either. I use a vacuum bleeder. If you are pumping the pedal to bleed the brakes, bench bleeding before installation probably has some benefits.


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## The Mexican Dub (Nov 8, 2006)

bench bleeding is absolutely necessary on a new master. 

If what you were told is right, and the pedal got a good feel when rear lines were pinched... then the master has nothing to do with it, the problem would be in the rear. 

You could pinch one side at a time to find out which wheel the problem is coming from. 

In my opinion the problem is the metering valve. Not the proportioning valve. (unless they are in the same assembly)

Your "weight adjustable" prop. valve ONLY works at panic stops to avoid the rear brakes from locking up and give you a controlled stop. It "senses" weight so it can increase or reduce the pressure depending on the car´s needs.

NOW... your METERING valve is there to restrict flow to the front brakes until around 100 psi has been built up in the system. This is with the purpose of overcoming the rear SHOE spring return tension and so to actuate all 4 brakes evenly on regular braking. 

So the metering valve is used in disc drum combinations, you have one and you don´t need it any more. Find it and get rid of it. 
Once again... if metering is found to be inside proportioning (combination valve), then you need the one from a 4 w disc car.


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## shwathebuck (Oct 5, 2008)

Well i changed the master out yesterday, bled a few times and now ive got brakes, but the pedal still feels a bit spongy. if i pump it once, i get amazing pedal pressure, but on the first depression of the pedal it goes about halfway down. my front rotors are gettin pretty outta whack and will be replaced soon. 

Ill look for a metering valve, but im pretty sure my car doesn't have one.. someone correct me if im wrong

Tomorrow ill re bleed all 4 corners again and if i don't have any better results ill throw a proportion valve from a 4 wheel disc car on it and see what i get.

As of right now, the car has stock brake lines up front, two stock rubber lines going to the rear beam and the two lines to the rear calipers are stainless braided. could that have something to do with this? the other 4 stainless lines will be going on soon, im just waiting on front rotors from Stoptech and then ill finish everything up.

Thanks again for the help, its much appreciated


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## germancarnut51 (Mar 23, 2008)

shwathebuck said:


> Well i changed the master out yesterday, bled a few times and now ive got brakes, but the pedal still feels a bit spongy. if i pump it once, i get amazing pedal pressure, but on the first depression of the pedal it goes about halfway down. my front rotors are gettin pretty outta whack and will be replaced soon.
> 
> Ill look for a metering valve, but im pretty sure my car doesn't have one.. someone correct me if im wrong
> 
> ...




If your pedal is still spongy, then you still have air in the brake lines, the rear brake shoe clearance is excessive, or the master cylinder you installed is defective.

Where did you get the master cylinder you installed? New? What brand? Used? How do you know that it's good?


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## shwathebuck (Oct 5, 2008)

germancarnut51 said:


> If your pedal is still spongy, then you still have air in the brake lines, the rear brake shoe clearance is excessive, or the master cylinder you installed is defective.
> 
> Where did you get the master cylinder you installed? New? What brand? Used? How do you know that it's good?



I got the Master cylinder from work, brand new. Its Centric Brand, and i know its good cause i have pedal pressure, im pretty sure i still have air in the lines. 

Forgot to mention, when i pulled the old master out, i got all the fluid out of it before hand, and when i pulled it off the booster, i noticed the booster was half full of brake fluid, so i drained it completely with a syringe and piece of clear tube. Im gonna bleed the brakes one last time tomorrow after work and see what i get.

Thanks again


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## germancarnut51 (Mar 23, 2008)

shwathebuck said:


> I got the Master cylinder from work, brand new. Its Centric Brand, and i know its good cause i have pedal pressure, im pretty sure i still have air in the lines.
> 
> Forgot to mention, when i pulled the old master out, i got all the fluid out of it before hand, and when i pulled it off the booster, i noticed the booster was half full of brake fluid, so i drained it completely with a syringe and piece of clear tube. Im gonna bleed the brakes one last time tomorrow after work and see what i get.
> 
> Thanks again


Some of the Centric stuff is CRAP, and some of it is good stuff (house marked major manufacturer stuff like: Axxis/Repco/PBR brake pads).

Other stuff is low cost Chinese made junk.

Personally, I would not use any generic parts. Obviously the master cylinder you got was made to be used on multiple cars (maybe not even all VWs). I'd return it myself. Just because you can get a part from work cheap, doesn't make the part worth installing.


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