Author Topic: Brake bleeding, brake fluid changes - IMPORTANT  (Read 26679 times)

Offline Teutonic_Tamer

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Brake bleeding, brake fluid changes - IMPORTANT
« on: October 17, 2010, 12:24:30 PM »
OK, I trust we all know the brake fluid must be changed every two years (at least).  :happy2:  And I also trust that some may also be aware that main stealers are supposed to hook up the VAS5051/5052 electronic diagnostic dooberys to 'cycle' the ABS/ESP unit, and that this can also be done with VCDS.

Now, I reckon many peeps (and indeed many main stealers - because they obviously didn't on my GTI  :fighting: - detail later) don't bother cycling the ABS/ESP when renewing the brake fluid.

Until now, my personal advice - for those of you who bleed your own brakes, was to try to use VCDS, but that it wasn't vital.  I've previously suggested to bleed the brakes using one of the conventional methods (either two-bod pumpy-pumpy, or with a one-man pressure bleeder), and then take the car for a spin, and 'exercise' the ABS/ESP systems (by doing a few hard stops on a slippery surface to activate the ABS, and a few wheelspins to activate the traction control).  And then go back and re-bleed the brakes.  And this was what I had previously done myself.

However, on my last brake fluid change, I did some experimenting.  I bled the brakes using the trad two-man pumpy method (200ml from left front, right front, left rear, right rear - then another 200ml from all four again).  I then hooked up VCDS and activated the relevant ABS functional tests (to activate all four individual circuits for 30 seconds) - and then bled all four again.  I was SHOCKED with the really black fluid which then came out.  It was clear to me that the fluid had been going stale in my ABS/ESP for four years.  :sick: :sad1: :mad: :scared: :fighting2: :stupid:


Now, the morale of this experience is very valid.  All VAG PQ35 platform cars (Golf Mk5, 8P A3/S3, TT Mk2, Leon Mk2, Octavia Mk2, Passat B6, Touran - and prolly some I've missed) all use a Continental Teves Mk60 ABS/ESP unit.  These Teves units are well-known to be unreliable.  The Touran forum is rife with real failures of these, costing owners £1500 to replace.  Many BMWs also use these Teves units, and again, are well-known to be very unreliable (especially when compared to the Bosch units which longitudinal Audis and Mercs, and Vauxhalls use).

So, I very strongly urge you all that you MUST activate the ABS/ESP unit via VCDS when changing brake fluid.  :smiley:
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Rob GTI

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #1 on: October 17, 2010, 01:31:38 PM »
Good timing this, I'm about to get my mechanic mate to change mine tommorrow. So how in VCDS and when do i activate the ABS pump, - I assume when emptying the current brake fluid??

Cheers. :drinking:
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Offline Rob GTI

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #2 on: October 17, 2010, 01:33:10 PM »
PS I would have hit the thank you button but can't see one in this sub forum  :laugh:
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Offline Teutonic_Tamer

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #3 on: October 17, 2010, 02:08:49 PM »
Good timing this, I'm about to get my mechanic mate to change mine tommorrow.
:happy2:


So how in VCDS and when do i activate the ABS pump, - I assume when emptying the current brake fluid??
OK, firstly, you should never 'empty' the old fluid (unless you are changing to a brake fluid from Satan - ie a silicone DOT5).  If your fluid in your master cyl resevoir is particularly manky, then syphon it off with a turkey baster or similar - but DO NOT then touch the brake pedal or open the nipples until it is topped up with fresh fluid.  If brake fluid is changed regularly, then it is simply a matter of pumping a quarter of a litre of fluid from each nipple, keeping the MC res topped up.

For using VCDS (or the OEM VAS5051 or VAS50502), you need a minimum of 11.5 volts in the battery.  Fire up VCDS, click on 'Select Control Module', 03-ABS brakes - then . . . . I can't remember (senior moment) . . . I think it is 'output tests' (or similar).  Basically, on the Golf, it takes you through various system functional tests for the four individual circuits.  If you have never done this before - you might sh!t yourself when the pedal starts grinding away really loudly - don't worry - this is perfectly NORMAL.  Oh, and if you are a weakling, you'll prolly get leg ache from holding the pedal so hard. :ashamed:  Now when it does its 'grinding' bit on each wheel circuit, you need to let it grind away for at least 30 seconds (this is what gives the leg ache!) for each wheel.

Then go round each wheel and bleed again.  Don't be shy about using 2 litres of fluid - more is definatly better in this respect.

Oh - and if you have a manual gearbox, don't forget to bleed your clutch too.

Then go and  :driver:

HTH
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Teutonic_Tamer

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #4 on: October 17, 2010, 02:10:37 PM »
PS I would have hit the thank you button but can't see one in this sub forum  :laugh:
Haha - wondered why my thank-you count was low! :sad1:

Maybe time to press the Admins into enabling thank-you function on the teccy sections!  :wink:
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Rob GTI

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #5 on: October 17, 2010, 05:41:38 PM »

So how in VCDS and when do i activate the ABS pump, - I assume when emptying the current brake fluid??
OK, firstly, you should never 'empty' the old fluid (unless you are changing to a brake fluid from Satan - ie a silicone DOT5).  If your fluid in your master cyl resevoir is particularly manky, then syphon it off with a turkey baster or similar - but DO NOT then touch the brake pedal or open the nipples until it is topped up with fresh fluid.  If brake fluid is changed regularly, then it is simply a matter of pumping a quarter of a litre of fluid from each nipple, keeping the MC res topped up.

For using VCDS (or the OEM VAS5051 or VAS50502), you need a minimum of 11.5 volts in the battery.  Fire up VCDS, click on 'Select Control Module', 03-ABS brakes - then . . . . I can't remember (senior moment) . . . I think it is 'output tests' (or similar).  Basically, on the Golf, it takes you through various system functional tests for the four individual circuits.  If you have never done this before - you might sh!t yourself when the pedal starts grinding away really loudly - don't worry - this is perfectly NORMAL.  Oh, and if you are a weakling, you'll prolly get leg ache from holding the pedal so hard. :ashamed:  Now when it does its 'grinding' bit on each wheel circuit, you need to let it grind away for at least 30 seconds (this is what gives the leg ache!) for each wheel.

Then go round each wheel and bleed again.  Don't be shy about using 2 litres of fluid - more is definatly better in this respect.

Oh - and if you have a manual gearbox, don't forget to bleed your clutch too.

Then go and  :driver:

HTH
[/quote]


So basically when you open the ABS pump via VCDS it lets the fluid into the system which is in turn bled out? I take it the clutch uses the same fluid as the brakes hence requiring to be bled?


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Offline Teutonic_Tamer

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #6 on: October 17, 2010, 05:47:45 PM »
So basically when you open the ABS pump via VCDS it lets the fluid into the system which is in turn bled out?
Basically, yes.  The ABS/ESP unit has its own integral hydraulic circuits and pumps.  During normal bleeding, these seem to be bypassed.


I take it the clutch uses the same fluid as the brakes hence requiring to be bled?
Yup, fed from the same resevoir on the brake master cylinder.
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Rob GTI

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #7 on: October 17, 2010, 06:37:15 PM »
Old fashioned thank you  :happy2:
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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #8 on: October 17, 2010, 07:24:03 PM »
Old fashioned thank you  :happy2:

You're welcome.  Let us know if you experience the same black flush!
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline john_o

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #9 on: October 17, 2010, 08:27:47 PM »
playing devils advocate then TT ...

why dont VW then specify that this is done at fluid change time ?

and if I activate the ABS the old fashioned way, will it not it some way mitigate the problem and flush/dilute some of the fluid?
(pretty easy if its wet) , albeit not very safe!
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Offline Teutonic_Tamer

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #10 on: October 18, 2010, 10:32:51 AM »
playing devils advocate then TT ...

why dont VW then specify that this is done at fluid change time ?
They do - categorically.  ELSA (the official VW electronic workshop manual) clearly describes, and STATES that the bleeding MUST be done with either VAS5051 or 5052.  The issue is that most VW stealers employ utter incompetent 'technicians' - one at my local can hardly read! - and those who can actually read can't be ar$ed to follow ELSA.  A classic example - how many stealers use a T40057 when changing oil on the 2.0 TFSI?


and if I activate the ABS the old fashioned way, will it not it some way mitigate the problem and flush/dilute some of the fluid?
(pretty easy if its wet) , albeit not very safe!
Not really.  That is how I have done it until recently, and it was pretty clear it didn't do the trick - brake fluid as black as coal is not good!  Modern ESP systems are considerably more 'technical' compared to just plain ABS systems.  ESP is a 'proactive' system, whereas ABS is 'reactive'.  Basically, an ESP will actively 'pre-charge' all four hydraulic circuits when the engine is running - older ABS didn't.

The other issue with activating the ABS is that it is very unlikely that all four circuits will be activated - never mind being activated long enough to usefully flush enough fluid through.
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline vRSAlex

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #11 on: October 18, 2010, 10:41:07 AM »
Great advice TT.  There are many garages that dont do this and even dont know how to do this.  Some of the fluid thats come out of ABS pumps ive replaced has been near sludge consistancy.

Make sure you ask the garage to bleed the ABS and if they cant then take it somewhere that can.

Its also worth asking them to bleed through the clutch too as many dont do that either.
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Offline Teutonic_Tamer

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #12 on: October 18, 2010, 12:13:04 PM »
Great advice TT. 
:happy2: :drinking:


There are many garages that dont do this and even dont know how to do this.
Agreed - and whilst it may be understandable for the small independent garage - it is completely disgraceful that official VW garages are not doing this.


Some of the fluid thats come out of ABS pumps ive replaced has been near sludge consistancy.
But the other killer of modern ESP systems is incorrect brake fluid.  Motul RBF600 and other 'race' fluids may be superb on the track - but they really fcuk ESP units.  I keep bashing on about the importance of this - only special low viscosity fluids should be used - which is why since 2006, the ONLY fluid officially permitted in by VWAG is one which meets VW501.14 - an ordinary DOT4, or even DOT5.1 fluids are not authorised by VWAG.


Its also worth asking them to bleed through the clutch too as many dont do that either.
Yup, agreed.   How do find clutch bleeding on Audi A4s?
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Offline dajonic

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #13 on: October 18, 2010, 12:20:58 PM »
You refer to bleeding the clutch on a manual. Is this not required on the DSG box?

Offline Teutonic_Tamer

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Re: Brake bleeding, brake fluid changes - IMPORTANT
« Reply #14 on: October 18, 2010, 12:34:06 PM »
You refer to bleeding the clutch on a manual. Is this not required on the DSG box?
Errrrrr . . . . . no!

Unless you have three pedals!
Sean - Independant Automotive Engineering Technician (ret'd)
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