# Is it ok to gravity bleed (full flush) MKIV Jetta's?



## Jon718 (Aug 14, 2007)

Just wondering if this is just as good as vacuum bleeding. I don't want to spend $50 on a Motul bleeder if this would work . (I gravity bleed my S2000 without any issues)


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## iamnobody1 (Oct 15, 2008)

*Re: Is it ok to gravity bleed (full flush) MKIV Jetta's? (Jon718)*

limit power bleeder to 10-12psi - make certain "if mt clutch hydraulics" master cylinder / clutch nipple does not leak
to fully purge brake fluid - reducing possibility of absorbed moisture - you really should cycle abs unit while bleeding each wheel - ie: fluid passes from master cyl reservior thru abs and out bleeder at each wheel individually = use vag or vagcom software command(s)
be certain you bleed in correct rotation - it is not intuitive


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## dirtymanpon (Jul 22, 2008)

*Re: Is it ok to gravity bleed (full flush) MKIV Jetta's? (Jon718)*

If your ABS goes dry you will have allot of problems. Just man up and roll some change or something and by the MOTIVE pressure bleeder.


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## Jon718 (Aug 14, 2007)

*Re: Is it ok to gravity bleed (dirtymanpon)*

Just curious, how would my ABS go dry? I am sucking all the OLD fluid out of my brake reservoir and replacing with NEW fluid (ATE Blue) and just cracking each bleeder one at time (albeit its slower w/o a vacuum bleeder)
So given my proceure how can the ABS go dry?


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## spitpilot (Feb 14, 2000)

*Re: Is it ok to gravity bleed (Jon718)*

You should be "pump" bleeding at least the last few times...Bentley reccomends pressure (or vaccum to flush fluid) followed by 5 pump bleeds (press on brake pedal, open blleeder, when fluid stops flowing, close bleeder and release pedal)..pump bleed makes caliper pistons move and helps drive out the last old fluid and air. Pressure bleeders obviously keep master cylinder full..vaccum or pump methods do not..you have to check often and replenish fluid. If you forget to do that and let master cylinder run dry and keep on bleeding either with vaccum or by the pump method you will "suck air" into the system and it will go first to the ABS valve block, which then needs to be cycled by a VAG com to get air back out..."moral of the story"...DO NOT let master cylinder EVER run dry while bleeding brakes! http://****************.com/smile/emthup.gif 
PS : Cheap vaccum bleeder..go to medical supply house and buy a "cathater flush syringe" (about 60cc, nylon syringe with tapered tip, no needle of course)..then get a foot or so of 3/16" PVC tubing at a hardware store or Home Despot...this will fit on bleeder and allow you to vaccum force the fluid from each caliper...then just go back with a helper and do the 5X pump bleeds...per Bentley method..and you're good to go!










_Modified by spitpilot at 8:39 AM 10-20-2008_


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## iamnobody1 (Oct 15, 2008)

*Re: Is it ok to gravity bleed (spitpilot)*

agreement w/ above
small entrained air bubbles in non-abs (active intervention - hydraulic pump/intensifier based) will gradually coalese into larger discrete air bubbles at hardline tee splits & rear proportioning valve & caliper fluid chambers
unfortunately with intro of active abs, this central module will gradually accumulated entrained air in accumulator/intensifier cylinder and fail to react immediately to control road wheel rate of rotation when called on by brake management mapping
this air in abs module will not bleed out unless module is cycled by software command(s)
air in abs may also contribute to "soft pedal" driver perception during normal brake application w/o abs functioning - although vacuum servo has a role in this perception
if you bleed brakes manually - not motive power positive pressure - not vacuum device - prepare a wooden block to place under brake pedal assembly to prevent full pedal stroke - 70% brake pedal stroke is enough to bleed brakes w/o bottoming out master cylinder piston assembly (which frequently happens when bleeding brakes manually) preserving leading edges of piston seals
gravity bleeding does not work on autos manufactured after 1996 due to smaller bore hardlines, active abs and smaller brake fluid system volumes - environment concerns re: fluid disposal
technology changes...


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## Jon718 (Aug 14, 2007)

Thanks for the all the input fella's. I woud getting the Motive bleeder and it was a breeze. The only issue was my brake fluid resoervoir overflowed onto the side. I'm not sure how that happened.


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