# mkiv how to bleed abs unit



## Badstuw (Sep 15, 2005)

is there any possible way to bleed the abs unit without using a vagcom? or even still just tell me the steps to bleed it since the bently doesnt list it. i just need the car rolling and the brakes working to move the car. thanks!


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## gunnr0991 (Aug 1, 2006)

*Re: mkiv how to bleed abs unit (Badstuw)*

Shouldn't need to bleed the ABS unit, unless you completely drained whole system, or opened ABS unit up.
If you do NEED to bleed it, there is no way to do it without the VAGCOM... or comparable computer.


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## jlsgli89-03 (Aug 25, 2003)

gunnr what do you mean if you do need to bleed it?are you talking about the abs unit itself? because this is the same question i have.i plan on buying the motive power bleeder.i can never seem to find the definate answer. you dont need a vagcom for a basic brake fluid change do you


_Modified by jlsgli89-03 at 8:05 PM 12-29-2008_


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## GT17V (Aug 7, 2001)

basic brake fluid change: don't need a VAG-COM.
ABS pump fluid change = need a VAG-COM & a few extra hands (makes it easier)


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## spitpilot (Feb 14, 2000)

*Re: (GT17V)*

The only time you'll have to bleed the ABS valve block is when you open system up to air above it by: letting MC run dry during fluid flush, replacing MC, and of course replacing the ABS valve block itself. To get air outa the valve block you need to "cycle the ABS" while bleeding the system..that cycling requires a VAG com input.


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## GTijoejoe (Oct 6, 2001)

*Re: (spitpilot)*


_Quote, originally posted by *spitpilot* »_The only time you'll have to bleed the ABS valve block is when you open system up to air above it by: letting MC run dry during fluid flush, replacing MC, and of course replacing the ABS valve block itself. To get air outa the valve block you need to "cycle the ABS" while bleeding the system..that cycling requires a VAG com input. <IMG NAME="icon" SRC="http://is.rely.net/2-64-38849-l-miLiM9RbflKgiExmFe7Gpw.gif" BORDER="0"> 

http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif 
The only other way to cycle the pump is to know the pinouts for the pump and run 12v to it. This is not done by the average joe for the risk of being wrong and damaging the modulator. This is normally never used for in vehicle applications either, but never the less its possible.


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## supadupagt4 (May 4, 2009)

*Re: (GTijoejoe)*


_Quote, originally posted by *GTijoejoe* »_
http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif 
The only other way to cycle the pump is to know the pinouts for the pump and run 12v to it. This is not done by the average joe for the risk of being wrong and damaging the modulator. This is normally never used for in vehicle applications either, but never the less its possible.

Sorry to bring this up.. but does anyone actually know the pin outs for the pump??
My car has no vag-com connector.
thanks,
tony.


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## GTijoejoe (Oct 6, 2001)

*Re: (supadupagt4)*


_Quote, originally posted by *supadupagt4* »_
Sorry to bring this up.. but does anyone actually know the pin outs for the pump??
My car has no vag-com connector.
thanks,
tony.


Opps, I actually forgot one small thing.... You can cycle the pump all day, but actually opening the internal valves in the block will require the input of the magnetic solinods, that is the proper way to cycle and bleed the modulator.
Reason: The passages from the MC to the 4 corners through the modulator's block are open by default, until the modulator needs to function and than it will close and open the valves for fluid passage as needed.
Sorry, you are SOL, the dealer will be able to cycle the pump, if no vag-com port than a harness directly to the modulator will be used just like in the factory.


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## supadupagt4 (May 4, 2009)

*Re: (GTijoejoe)*

Know if i can make a harness??


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## HilF (Jan 10, 2004)

*Re: (GTijoejoe)*


_Quote, originally posted by *GTijoejoe* »_
Opps, I actually forgot one small thing.... You can cycle the pump all day, but actually opening the internal valves in the block will require the input of the magnetic solinods, that is the proper way to cycle and bleed the modulator.
Reason: The passages from the MC to the 4 corners through the modulator's block are open by default, until the modulator needs to function and than it will close and open the valves for fluid passage as needed.
Sorry, you are SOL, the dealer will be able to cycle the pump, if no vag-com port than a harness directly to the modulator will be used just like in the factory.

joe, could you elaborate a bit. so are you saying that you cannot access the mag. sols. with the vagcom?
reason i ask is i have bled my brakes more than i care to remember. always mushy. MC is good. pads aren't soft pads. slide pins are good front and back. front actually are not the rubber ones. only thing i can think of is air in the pump somewhere. i have bled while cycling the pump via vagcom, but still crap.
am i missing something? gravity bleed? 
/threadjack


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## GTijoejoe (Oct 6, 2001)

*Re: (white_r!ce)*


_Quote, originally posted by *white_r!ce* »_
joe, could you elaborate a bit. so are you saying that you cannot access the mag. sols. with the vagcom?
reason i ask is i have bled my brakes more than i care to remember. always mushy. MC is good. pads aren't soft pads. slide pins are good front and back. front actually are not the rubber ones. only thing i can think of is air in the pump somewhere. i have bled while cycling the pump via vagcom, but still crap.
am i missing something? gravity bleed? 
/threadjack









Oh no, thats not what I am saying. The poster said he didn't have a vagcom hook up.
The vagcom will certainly cycle the pump and the valves. Did you try a pressure bleeder with a vagcom?


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## GTijoejoe (Oct 6, 2001)

*Re: (supadupagt4)*


_Quote, originally posted by *supadupagt4* »_Know if i can make a harness??


I see, you could, but the problem is knowing the pinouts of the harness. That type of info is secret, only the supplier and vw R&D (upon request) would likely have that type of info.


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## HilF (Jan 10, 2004)

*Re: (GTijoejoe)*


_Quote, originally posted by *GTijoejoe* »_
Oh no, thats not what I am saying. The poster said he didn't have a vagcom hook up.
The vagcom will certainly cycle the pump and the valves. Did you try a pressure bleeder with a vagcom?

yup. pressure bleeder with vagcome cycling with buddy bleed















maybe i should check taper of my pads... been meaning to do that.


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## rocco2gti (Nov 11, 2004)

*Re: (white_r!ce)*

I've heard that cycling the ABS pump (brake hard enough to activate the ABS) works


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## Skimmer (Jun 18, 2021)

I've had this issue with multiple vehicles with ABS. I can't promise this fix will work every time but its sorted problems for me in the past. After completing a normal bleed of the system, use a stick or weight to pin the brake pedal down and leave overnight. This allows the more complex vessels in the circuit to equalise on pressure and release any air to the reservoir if possible. 
Hope this helps.


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