Proper brake bleeding order?

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ruckman101
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Proper brake bleeding order?

Post by ruckman101 » Sun Sep 30, 2012 12:39 pm

Have a new master cylinder in, going to change all the brake hoses today, and so someone please correct me if I'm wrong, but when bleeding a brake system, I start at the wheel furthest from the master cylinder and work my way to the closest wheel to the master cylinder, yes?

And one other note, when disconnecting the two brake lines from the old master cylinder, the brake fluid in the chamber towards the rear of the car was under pressure, spraying when released, unlike the front chamber. Is this an indication of constricted hoses, or is it that the small port that feeds and relieves the chamber of fluid is blocked by crud, again, probably from deteriorating hoses? The reservoir on top of the master cylinder was certainly full of black crud.



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Amskeptic
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Re: Proper brake bleeding order?

Post by Amskeptic » Sun Sep 30, 2012 1:25 pm

ruckman101 wrote: when bleeding a brake system, start at the wheel furthest from the master cylinder and work to the closest wheel to the master, yes?


Yes, but note that it does not matter if you start at the front or the rear with dual circuit brakes so long as you do the furthest for the circuit you are working on and work your way in.
ruckman101 wrote: brake fluid in the chamber towards the rear of the car was under pressure
Is this an indication of constricted hoses, or is it that the small port that feeds and relieves the chamber of fluid is blocked by crud?
Either or both . . . could cause the above symptoms.
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Re: Proper brake bleeding order?

Post by ruckman101 » Sun Sep 30, 2012 3:05 pm

Thanks. Front hoses looked ok. However the new Mehle replacements did not have the extra rubber insulator that fits into the clips just outside the drum. Sliced off the old ones and put them on the new hoses.


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Re: Proper brake bleeding order?

Post by ruckman101 » Wed Oct 03, 2012 12:36 pm

Sigh. The plug I used to block the unneeded third brake line on the new master cylinder isn't plugging. It seeps. Discouraging to have put all this effort in and the brakes are no better than when I started. I thought about teflon tape, as the plug is for a plumbing application, but I wrapped the plug in teflon tape before installing it and soaked it in used brake fluid and the tape softened and thinned after ten minutes or so. There must be actual plugs designed for this application. FLAPS?


neal
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Re: Proper brake bleeding order?

Post by kreemoweet » Thu Oct 04, 2012 3:32 pm

You used the proper metric tapered pipe plug (M10x1)? If you tried to use a 1/8" NPT plug, the threads in the M/C or residual pressure valve
are likely damaged, but probably fixable with a tap. It's very doubtful if any FLAPS would have metric plugs, but Googling "metric pipe
plug" turns up several on-line sources. Other possibilities: a (shortened) M10x1 bolt with sealing washer; an old brake line end
cut off short, crimped and filled with solder; an old brake lite switch.

I don't know if it actually matters, but VW/Bentley actually went to the trouble to specify a brake bleeding sequence of R. front > L. front >
R. rear > L. rear.

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Re: Proper brake bleeding order?

Post by hambone » Fri Oct 05, 2012 11:35 am

Great stuff! How the hell do you know that off the top o' your head?
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Re: Proper brake bleeding order?

Post by ruckman101 » Fri Oct 05, 2012 2:40 pm

Tightened way beyond spec, but the brass plug from the FLAPS seems to have done the trick. Whew.



neal
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Amskeptic
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Re: Proper brake bleeding order?

Post by Amskeptic » Sat Oct 06, 2012 8:19 am

kreemoweet wrote:
I don't know if it actually matters, but VW/Bentley actually went to the trouble to specify a brake bleeding sequence of R. front > L. front >
R. rear > L. rear.
The benefit of doing the front circuit first, is that it fills/pressurizes the end of the master cylinder, giving you better "push" for the longer path of the rear circuit.
Colin
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Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Proper brake bleeding order?

Post by ruckman101 » Mon Oct 08, 2012 12:56 am

Amskeptic wrote:
kreemoweet wrote:
I don't know if it actually matters, but VW/Bentley actually went to the trouble to specify a brake bleeding sequence of R. front > L. front >
R. rear > L. rear.
The benefit of doing the front circuit first, is that it fills/pressurizes the end of the master cylinder, giving you better "push" for the longer path of the rear circuit.
Colin

Perfect sense. Even more so for acclimatizing a new master cylinder to the system, along with four new brake hoses. Bertha Bus did well on her first run into town yesterday. Even under a moment of panic and heavy application. Still, it itches at me that I should do one final bleed of the system. My experiences with the recently purchased vacuum brake bleeding tool at this point are overwhelmingly disappointing.


neal


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Re: Proper brake bleeding order?

Post by Amskeptic » Wed Oct 10, 2012 5:39 am

ruckman101 wrote:My experiences with the recently purchased vacuum brake bleeding tool at this point are overwhelmingly disappointing.

neal
They are by their very design wrong. Do NOT apply a vacuum through a pressure system. A pressure bleeder with a very modest 3-5 psi from the reservoir on down is perfect.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Proper brake bleeding order?

Post by hambone » Wed Oct 10, 2012 4:41 pm

6 psi pressure bleeder on the Squareback, and the brakes were fine on that fateful day without windows or latches. It's a handy way to do it alone.
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Re: Proper brake bleeding order?

Post by 72Hardtop » Wed Jul 19, 2017 8:32 pm

Have never had an issue using a Mighty vac when bleeding brake/s on a VW.
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Re: Proper brake bleeding order?

Post by sgkent » Wed Jul 19, 2017 9:17 pm

Mighty vacs have never done it for me. Put your spouse or a friend in the driver's seat and have them work the pedal. If you don't know how ask. A pressure bleeder works good too for one person bleeding and they aren't all that expensive. A really good Mighty Vac can be ruined by brake fluid.
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Re: Proper brake bleeding order?

Post by Bleyseng » Thu Jul 20, 2017 6:57 am

sgkent wrote:
Wed Jul 19, 2017 9:17 pm
Mighty vacs have never done it for me. Put your spouse or a friend in the driver's seat and have them work the pedal. If you don't know how ask. A pressure bleeder works good too for one person bleeding and they aren't all that expensive. A really good Mighty Vac can be ruined by brake fluid.
Yep been there done that! I prefer the tried and true helper pushing the brake petal while I drain each brake cylinder. "Push......Hold.....Push....."
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Re: Proper brake bleeding order?

Post by asiab3 » Thu Jul 20, 2017 10:58 pm

Vacuum bleeding technique can be rendered useless by loosening the bleeder screw too much, to the point where the vacuum apparatus starts to suck air from around the bleeder threads. Many people do this and have miserable results. I've seen it done poorly, and done well, and I absolutely think there is more skill involved with that technique.
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