# Mk2 rear disc conversion fail /please help



## Diablo_coupe (May 13, 2012)

Hi guys need help did mk2 rear disc conversion over the weekend mk4 calibres and carriers,mk 3 spindles and rotors car stops but the pedal is super mushy it feels like they don't engage till pedal is half way to the floor any help is greatly appreciated


----------



## germancarnut51 (Mar 23, 2008)

Diablo_coupe said:


> Hi guys need help did mk2 rear disc conversion over the weekend mk4 calibres and carriers,mk 3 spindles and rotors car stops but the pedal is super mushy it feels like they don't engage till pedal is half way to the floor any help is greatly appreciated


How did you use MKIV rear carriers with MKIII spindles?


----------



## bengone1 (Jun 17, 2003)

You may need to remove the rear caliper from the carrier and hold it so the bleed screw is the highest point. Compress/hold back piston with a C-clamp and proceed to bleed.


----------



## Humble Mechanic (Jun 16, 2011)

Sound like they still have air in the lines..


----------



## lnoriel (Jul 31, 2000)

bengone1 said:


> You may need to remove the rear caliper from the carrier and hold it so the bleed screw is the highest point. Compress/hold back piston with a C-clamp and proceed to bleed.


Bengone1 is right. The MKIV aluminum calipers, when mounted, position the bleeder valve facing downward. This orientation makes it likely to trap an air bubble inside the top of the caliper since the bleeding evacuates air through the downward facing valve. 

Follow Bengone1's advice.


----------



## germancarnut51 (Mar 23, 2008)

lnoriel said:


> Bengone1 is right. The MKIV aluminum calipers, when mounted, position the bleeder valve facing downward. This orientation makes it likely to trap an air bubble inside the top of the caliper since the bleeding evacuates air through the downward facing valve.
> 
> Follow Bengone1's advice.




No, you mounted the calipers upside down. The one in the photo is on the wrong side. On MKIIIs and MKIVs the factory parking brakes cables and the brakes hoses don't go like that.

The parking brake cables are supposed to run under the trailing arms and under the calipers, curving back up behind the calipers.

The calipers hoses are supposed to run over the tops of the trailing arms to the calipers. The bracket in the photo that is supporting the parking brake cable is supposed to be pointed up, and supporting the junction of the metal line running back from the front of the trailing arms where the caliper hose connects. Then the caliper hoses run the short distance to the calipers. You have to dremel a short slot in/on the support bracket so the indexing lug on the hose will fit and support the hose. Then you can tighten the fitting on the metal line onto the hose without another wrench to counter hold. (the MKII/MKIII hose has a hex so you can counter hold the hose while tightening the fitting from the metal line). 

The metal lines on MKIIIs with rear disc brake cars are shorter than the metal lines that come of drum brake cars and go directly from the front of the trailing arms into the drum brake wheel cylinder. Some people bend the metal line into a pretzel to shorten it, but it makes more sense to me to get the correct brake lines when you convert from drums to MKIV disc calipers. That means either getting the shorter MKIII rear disc brake metal lines, and Passat hoses, OR MKIV hybrid/composite lines that go from the front of the trailing arm with metal, and have a rubber hose permanent crimped on (must change the whole thing when the ribber hose leaks) and run all the way to attach to the MKIV brake caliper.


----------



## bengone1 (Jun 17, 2003)

That pic is definitely not going to bleed. I have seen it were you swap calipers and the bleed screw is just a little off dead top and you are left with an air bubble.


----------



## lnoriel (Jul 31, 2000)

*interesting*

I would imagine your description would work. What you are looking at is the ECS conversion kit installed on a GTi rear disc beam. Im fairly confident I followed all instructions and bought all new parts per instructions. 

Of course the calipers didn't exist when this axle beam was in production. I did try them on the other side and the supplied hydraulic lines would not reach. I guess it would be possible as you suggest to use different length hydraulic piping and extended length brake cables. Then changing the orientation from the top to the bottom. 

If this is incorrect, then I was misinformed while making parts selection


----------



## germancarnut51 (Mar 23, 2008)

It's been over four years since I've owned a MKII, so the details are getting fuzzy. 

I would definitely reroute the fluid lines and the parking brake cables to the MKIII/MKIV design myself. I don't care for the brake lines running under the trailing arms and exposed to road debris. 

And taking the calipers off to bleed them would be an unnecessary PITA.


----------

