MK4 Golf ABS brake system NIGHTMARE!!!!

[24V Renshaw 0]

OK.

 

As many of you know I have installed absolutely everything from a MK4 Golf into my Corrado. This along with the wiring loom, engine etc.. includes the complete brake system, servo, master cylinder, pipework, ABS unit, calipers (front and rear).

This is where my problem lies.

The system will not work. I can get a semi firm pedal when I bleed it, but as soon as the engine runs and there is vacuum assistance the pedal goes straight to the floor, which is the tell tail sign of an air lock. I tried everything I could, using Vag-com, not using Vag-com, pressure bleeding, manual bleeding, cracking pipes at different parts of the system everything.

So for the first time in my life I booked one of my cars into VW. I thought, they have the proper machine, the knowledge (ish) the instructions everything. They bled the brakes this morning. Exactly the same problem! :roll: :mad: :mad:

 

So I am stuck. They could find nothing wrong with the system as such and the electronics side of things worked fine.

 

My next step is to remove the ABS unit completely and just bypass it.

If that works then I will try and find a MK4 Golf breaking where the fluid has not been drained from the ABS unit and then fit that in place of my old one, as I am fairly convinced it must be the ABS unit that has the air lock in it.

 

If that doesn't work, I give up!!

 

Jay

[Supercharged 2]

Didn't PhatVR6 recently have the same sort of problem?

[davidwort 0]

OK.

 

As many of you know I have installed absolutely everything from a MK4 Golf into my Corrado. This along with the wiring loom, engine etc.. includes the complete brake system, servo, master cylinder, pipework, ABS unit, calipers (front and rear).

This is where my problem lies.

The system will not work. I can get a semi firm pedal when I bleed it, but as soon as the engine runs and there is vacuum assistance the pedal goes straight to the floor, which is the tell tail sign of an air lock. I tried everything I could, using Vag-com, not using Vag-com, pressure bleeding, manual bleeding, cracking pipes at different parts of the system everything.

So for the first time in my life I booked one of my cars into VW. I thought, they have the proper machine, the knowledge (ish) the instructions everything. They bled the brakes this morning. Exactly the same problem! :roll: :mad: :mad:

 

So I am stuck. They could find nothing wrong with the system as such and the electronics side of things worked fine.

 

My next step is to remove the ABS unit completely and just bypass it.

If that works then I will try and find a MK4 Golf breaking where the fluid has not been drained from the ABS unit and then fit that in place of my old one, as I am fairly convinced it must be the ABS unit that has the air lock in it.

 

If that doesn't work, I give up!!

 

Jay

 

I'm pretty sure that's the problem, I'll check with my Dad this evening, but I'm sure ABS pumps can be a real problem if the system has been completely drained, I think what they usually do is remove most of the reservoir's fluid by pipette and then fill it with fresh and bleed the system through but without ever fully draining the system, providing it's just a fluid replacement at a service.

I'll try to find out but it's worth asking the dealer what the workshop manual says about fitting a new abs unit and how the system should be filled and bled afterwards.

 

David.

[Kevin Bacon 5]

Sounds like fun! Agreed on the ABS pump being the most likely suspect, but have you tried another Master Cylinder to be sure?

 

When it's working can you let me know what the initial bite feels like? I found MK4s are over servo'd and you can end up head butting the screen when brushing the pedal with as much force as you would in a Corrado VR6. Although the VR's soft and long pedal is good for brake modulation and feathering speed off, it can sometimes catch you out....especially when driving a car that has sharp brakes for a while.

 

So I'm looking for a suitable upgrade! MK4 is too sharp imo, something inbetween the two extremes would be nice.

[24V Renshaw 0]

Supercharged - Yes he did but Phat has a Corrado ABS unit which is different. Plus I have done everything he did and still no joy.

 

David - Anything you can find out would be very useful. I will be having a long chat with the VW tech to find out what they have done.

 

Kev - If I ever get it working I will let you know!

 

This is driving me nuts!!

 

Jay

 

Jay

[davidwort 0]

Supercharged - Yes he did but Phat has a Corrado ABS unit which is different. Plus I have done everything he did and still no joy.

 

David - Anything you can find out would be very useful. I will be having a long chat with the VW tech to find out what they have done.

 

Kev - If I ever get it working I will let you know!

 

This is driving me nuts!!

 

Jay

 

Jay

 

OK, here's the best info I can get,

you definately need to pressure bleed the system due to all the small valves inside the ABS units, they are really difficult to get bled if they have been completely drained of fluid (well I guess you know that already), and removing the units and shaking them from every angle etc.. it's still almost impossible to get air locks out, he did say that it is unlikely to be the unit itself that is damaged and if you follow the workshop manual to the letter (did VAG do this?) and pressure bleed, that's pretty much the only way.

 

David.

[Supercharged 2]

If it was VAG then they should all have pressure bleeding units and boy are they quick! - had the brakes on my mums car bled on the weekend and it took about 10 mins to do all 4 lines!

[RW1 0]

I'll check with my Dad this evening, but I'm sure ABS pumps can be a real problem if the system has been completely drained

 

Bob on!

 

Jay,

 

Straight from the Mk4 Workshop manual for a brake system with ABS.....

 

"Only remove the sealing plugs on the replacement hydraulic unit when the corresponding brake pipe is going to be fitted."

 

"If the sealing plugs are removed too early, brake fluid can escape (obvious!), it can then no longer be guarenteed that the unit is sufficiently filled or adequately bled."

 

So, you need some sealing caps or similar for each pipe connection for the next scrap car donor.

 

(Same applies for the original Corrado ABS valve block)

[CoxyLaad 0]

wasnt phats problem something to do with his calipers though?