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Discussion Starter · #1 ·
PLease Help!

I'm currently building a corrado and, nearing completion, I have come to the brakes. I have basically transfered everything from a Mk4 2.3lt V5 into my corrado, Engine, loom, brakes front hubs etc etc...the lot.

The trouble I'm having is that what ever I seem to do I cant get a good pedal feel. I have folowed the procedure I have found on the net: Bleed each corner in sequence, rear driver, rear passenger, front driver, front passenger. Then run the 'output test' using Vag Com which I'm led to beleive does its thing and creates the hard pedal pressure.

After doing this sequence I get a moderatley stiff pedal but as soon as I turn the engine on and the servo assistance come in the pedal is soo soft it could flap about in the wind! This is sooo frustrating as I have now bled the thing about six times (take shares out in brake fluid companies!)

If someone out there has experienced this before please help I really could do with an idiots step by step guide to how to do it correctly.

or if anyone out there have the bentley workshop manual on the MK4 this should detail the procedure.

Any help you can offer is greatly appreciated.

For you information the set up I'm running is:

Mk4 Master cylinder and pedal box,

Mk4 ABS ESP pump

Mk4 rear calipers

all the above is from a MK4 2.3lt V5 (2000 year)

I have front calipers from a Porsche 911 (1995 carrera - non turbo)

Many thanks,

Doug
 

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I'm guessing here, but don't you need to do some sort of bleed using VAG-COM or else you may still have air within the ABS pump system?

When you say that you have bled each corner, did you do this using VAG-COM or the traditional pumping the pedal method? If the latter, I know you can use VAG-COM to operate the ABS pump and remove the need to push the pedal down, and this may be more effective at flushing out air from the ABS system components.

Chris
 

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Quote: posted by type40 on 09/11/2004 10:19:38

Bleed each corner in sequence, rear driver, rear passenger, front driver, front passenger. Then run the 'output test' using Vag Com which I'm led to beleive does its thing and creates the hard pedal pressure.

Did you actually bleed each corner using VAG-COM to provide the pressure? This paragraph only says that you used it after bleeding.
 

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Discussion Starter · #5 ·
Ahhhh, I see what you mean. I did try that aswell the pump seemed to push loads of fluid out of the front passenger caliper but not the others.

Every other time I have bled the system I used the pressure bleed technique.
 

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When you tried to bleed using VAG-COM, did you release only one bleed screw at a time or did you have all 4 open at the same time (in which case it could well dump all the fluid from only one caliper)?

I must stress that I've never used this technique before, but from what I understand it is necessary to operate the pump to force the air from this part of the system out before you bleed the lines, or else that air will remain in the system. I would therefore suggest that you set the pump going and then go round each caliper in turn, probably starting at the front and release the bleed screw until you get a clear bubble-free stream of fluid through.

Chris
 

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I should also have added that Weelon on this forum or Techie can probably tell you the exact procedure as they are VAG technician - it might be worth sending them a PM or email.

Chris
 

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Discussion Starter · #8 ·
I only had the one bleed nipple open at a time.

Hmmm? I may well give that a whirl tonight. If I have any hair left after pulling it all out on this problem. The idea behind me building my car was to do 100% of the work myself. So far I've done all the conversion stuff, painted it, fitted RS4 seats and even made and trimmed a custom dashboard in leather. I would really begrudge taking it to a garage to have a spanner monkey fix it, a fail to see it being that hard!? I'm certain I'm missing something super simple...?

Doug
 

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Discussion Starter · #10 ·
Ok, Update after another try last night.

I managed to get the best feel out of the pedal last night with it only moving about 2-3 inches before getting stiff (Oooo errr) the procedure followed was:

Pressure bleed: Rear Drivers

Rear Passenger

Front Drivers

Front Passenger

Then, open front passenger nipple and run the pump via vag com.

Close Nipple.

Then continued throught the Vag Com process left pedal press pedal etc etc whilst it controlled different valves and pumping etc.

This is where I thought I was on a winner stiff (ish) pedal so started the engine and ......pedal goes super light and travels straight to the floor!!! Urgh! after turning the engine off again the pedal did not return to the stiffness I had before running the engine. This is leading me to think there is a problem in the system somewhere!

Surely if the system is completely full with fluid it doesn't matter how much servo assistance there is it can only push the fluid so far!?(just enough to press the pads to the discs)

Any ideas????

Doug - even less hair now!
 

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without looking at a hydraulic circuit diagram, I wouldn't kinow which to have a look at, but it seems that you are trying allsorts, it maybe a problem with the master cyl or servo.

Just a thought, a lot of the problems we seem to have at work turn out to be where you would least expect. I run a team fixing helicopters for the Royal Marines.

Dave
 

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Discussion Starter · #14 ·
I would ahve thought I could work it out as I'm a mechanical design engineer (automotive!) I've tried to find a schematic diagram off the net but no joy it seems the fluid goes into the abs unit where 'magic happens' and you stop!

One thing I do know is that I have replaced the master cylinder so thats off the list. it could well be the ABS unit as I had all the parts sitting about for a year before fitting, I guess seals could have perished etc????

I'm going to start blocking of parts of the system tonight to try and determine where the problem is and, once found, why its bust. I really hope to find something broken, then atleast I know what has been causing it!

Doug
 

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You learn something new on this forum daily, i didnt know that you could use vag com to bleed the air from the braking system, id imagine that i could use vag com to renew my brake fluid then as well then , couldnt I?
 

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Discussion Starter · #17 ·
Thanks guys will do, expect news tomorrow.... in the mean time I think you've all earnt a picture of this beast... not to give too much away but this is the state the engine conversion is looking at the moment - all coments are welcome..... C:\Documents and Settings\dlarkin\Desktop\pic_009.jpg

Doug
 

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Mate, you photos need to be on the web somewhere, you've linked it direct from your hard drive. Only hackers can see it!
 
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