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So I ordered a new german master cylinder, gunna be my first
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FreakCitySF
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PostPosted: Tue Mar 13, 2007 10:25 pm    Post subject: So I ordered a new german master cylinder, gunna be my first Reply with quote

attempt at replacing a master cylinder.

I also will buy the hand pump/vacuum kit.
Similar to this:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92474


What should i look for?

I was wondering should i drain all the old brake fluid? or just put in new fluid?

Can i drain the fluid with the hand pump vacuum?

I have to bench prime? the master cylinder? whats the phrase? and what do i do exactly?

Thanks in advance

Kinda nervous about this
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Ferretkona
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PostPosted: Tue Mar 13, 2007 10:43 pm    Post subject: Reply with quote

I would not worry about bench priming. Best preformed by the pros and it can still leave bubbles.

Bolt it all up and use the vaccum pump. Be aware the pump will drain the reservoir quickly, every few pumps check and refill the reservoir.

Start at the right rear, then the left rear, followed by the front right and finish on the front left. If you buy a quart you should be ok with brake fluid, do not reuse!
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Towel Rail
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PostPosted: Wed Mar 14, 2007 12:55 am    Post subject: Reply with quote

For that $25, you could buy a case of beer and invite a friend over to help... Wink
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Woreign
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PostPosted: Wed Mar 14, 2007 5:11 am    Post subject: Reply with quote

A case of beer and a couple of burgers too!
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KTPhil Premium Member
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PostPosted: Wed Mar 14, 2007 9:34 am    Post subject: Reply with quote

Doing the job by myself this time, I'm going to use a vacuum pump like the one shown. I also bought a spare reservoir cap, which I will drill for a fitting. From that fitting I will run a clear hose to a large jar full of brake fluid, propped at the right height to act as a siphon to keep the reservoir full as I suck out fluid from each wheel in turn. That's my plan, but I always used a buddy with a strong right leg to help me before.
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FreakCitySF
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PostPosted: Wed Mar 14, 2007 12:43 pm    Post subject: Reply with quote

So should i clean out any old brake fluid? or ok just to put new fluid in?

If I should clean out old brake fluid, how do i go about doing that?

So agreeed no need to bench prime it, just bolt it on, new fluid and pump it a few times? same affect as bench priming?

I have to work this out in my head completley before i even start! haha
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KTPhil Premium Member
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PostPosted: Wed Mar 14, 2007 2:46 pm    Post subject: Reply with quote

Bleed out all the old fluid, replacing it with new fluid after every few pumps; it won't backflush much, and if you keep it up until only clean fluid comes out of the wheel cylinders/calipers, yuo will be fine. You might even want to do this with your old master just to be sure no crap backflows into the new one from the lines.

If you have really dirty fluid then you might want to replace your flex lines. Not a bad idea in any case.

Some bench bleed because they just can't seem to get all the air out later without bench bleeding first. The simplest way I've seen is to immerse the master in a jar full of fluid, then pump the piston with a large phillips screwriver, until no air comes out of the outlet ports. Then cap them (using the caps that come with a new MC), dry it off as best you can (becfause brake fluid makes great paint remover), then go ahead and install it. That's my plan.
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eastwood420247
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PostPosted: Fri Mar 16, 2007 6:56 am    Post subject: Reply with quote

Woreign wrote:
A case of beer and a couple of burgers too!

yes indeed
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uberautowerks
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PostPosted: Fri Mar 16, 2007 9:42 am    Post subject: Reply with quote

Skip the vacuum pump, unless your breast feeding! I've had problems with the vacuum pulling air past the bleeders threads.
Here's what I do, I've used this technique for years and can bleed an entirely new system in less than an hour, by myself!
-You need a clear plastic bottle with a screw on cap, I use a Gatorade bottle, and six feet of clear tubing from the home improvement store that will fit snug over the bleeders.
-Drill a hole in the bottle cap for the hose, kinda snug, than a little hole next to it, for air to exit.
-Pour an inch or two of clean fluid into the bottle, push the clear hose into the bottle until the end of the hose is submerged in the fluid.
-Press the other end of the clear hose over the bleeder, put the bottle on the fender or hood or anywhere you can watch it while pumping the brake pedal.
-Open your bleeder a bit (Always start at the right rear, then left rear, then right front) and depress the brake pedal, slowly, all the way to the floor, hold there for a second, release the pedal and repeat.
-You'll notice the air bubbles working through the clear tubing while you move the pedal down and while you are holding the pedal down. When you release the pedal you'll see the bubbles start back down the line, but that's OK as the bubbles move a lot faster out then in.
-Do this for all four wheels and keep working the pedal until the brake fluid runs clear and don't forget to check the level in the reservoir often.
-Try it, you'll love it. I scoffed the first time it was suggested to me, then tried it years later. Now I wish I had all my wasted time back!
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GeorgeL
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PostPosted: Fri Mar 16, 2007 9:54 am    Post subject: Reply with quote

I don't really get the whole "bench bleeding" thing. Sure you can bleed the cylinder under a bath of brake fluid, but as soon as you take the cylinder out of the fluid air will get in and ruin the effort.

VW never mentions bench bleeding either.

Just bolt the cylinder up, fill the reservoir and bleed. Follow the order in the service manual. Some models start with the front, some with the rear.

Run a piece of clear tubing from the bleeder into a catch container. Have your helper pump the brakes a couple of times and hold it down. Open the bleeder and let air/fluid escape. Close the bleeder and tell your helper to pump and hold again. Repeat until nothing but clean new fluid comes out.

If you happen to know someone who works in a hospital or medical supply outfit, have them get you an oxygen hose. They're clear, small in diameter, and they have a very nice connector that fits the bleeder perfectly.
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uberautowerks
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PostPosted: Fri Mar 16, 2007 10:13 am    Post subject: Reply with quote

I never got the bench bleed idea either, what with all the hols in the master! I know you must have fluid in the cylinder before you move the pedal.
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Ian Epperson
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PostPosted: Fri Mar 16, 2007 10:34 am    Post subject: Reply with quote

uberautowerks wrote:
I never got the bench bleed idea either, what with all the hols in the master!


I thought you were only supposed to cross-drill the rotor!?! Wink


The corss drilled brake lines make you go faster, hadn't thought about the master.


Last edited by Ian Epperson on Fri Mar 16, 2007 1:14 pm; edited 1 time in total
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bucko
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PostPosted: Fri Mar 16, 2007 12:27 pm    Post subject: Reply with quote

You always remember your "first time"......
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FreakCitySF
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PostPosted: Fri Mar 16, 2007 9:49 pm    Post subject: Reply with quote

So what's the consensus say, bleed each line, or hand vacum kit, I'm pretty sure I understand both ways.

Just curious when your bleeding the brakes, old fashioned way, how many pumps do you need? 2-3? then tell the person to hold it down until you say its clear?
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Spezialist
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PostPosted: Fri Mar 16, 2007 10:06 pm    Post subject: Reply with quote

TSB=#1 wrote:
Bleed the master on the bench
after install bleed closest bleeder
then next closest and so on.
all with a simple rubber hose attached to the bleeder with the other end in said beer bottle "submergered" in brake fluid.
Lashed together with bailing wire.
press pedal slowly until all all air bubbles escape, you watch it escape under the car, while pumping gently with your hand.
Remember to keep reservoir full.
New fluid will pump out all the old crap.
All done by your self with extra money for beer and German Parts.

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uberautowerks
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PostPosted: Sat Mar 17, 2007 7:21 pm    Post subject: Reply with quote

How many pumps? Kinda like how many licks to the tootsie roll center! No really, keep pumping until no more bubbles come out, then your helper holds the pedal down while you tighten the bleeder.
-Do it with the container and the submerged hose and you don't need a helper, but keep stroking the pedal until the bubbles stop, AND the fluid is clear.
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--- The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair.
- Douglas Adams -
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'71 Single cab (White too)
'70 Weekender (White three)
'05 Evolution VIII (White also!!!)
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74 Thing
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PostPosted: Sat Mar 17, 2007 10:09 pm    Post subject: Reply with quote

I bought this http://aircooled.net/new-bin/viewproductdetail.php?keyword2=TZE0055&cartid=

Works great! I was tired of getting a helper pump while I was underneath dealing with the bleeder valve. Plus it is kind of like a professional unit only it does not use air pressure by an air compresser. Make sure you tighten your brake shows before and clean the container with rubbing alcohol when you are done. It is a quick way to flush the system and add new brake fluid too!!
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Ian Epperson
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PostPosted: Sat Mar 17, 2007 10:42 pm    Post subject: Reply with quote

74 Thing wrote:
I bought this http://aircooled.net/new-bin/viewproductdetail.php?keyword2=TZE0055&cartid=

Works great!


Looks like a great little device! I would have guessed that it would cause the filler lines to leak though as they're not designed for much pressure - but I guess it doesn't require much pressure when the bleeder is open.

Can it do all 4 at once, or does it end up just pushing fluid out of the closest or least resistant line? I usually use fishtank air tubing and an old jar - 4 of those are cheap and doing all 4 at once is tempting...! Or maybe you could rig up each one, give a bunch of pumps, then close any valve that is showing clear fluid, pump some more, close more valves, etc.

Now where's my credit card... Cool
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GeorgeL
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PostPosted: Sun Mar 18, 2007 11:53 am    Post subject: Reply with quote

FreakCitySF wrote:
So what's the consensus say, bleed each line, or hand vacum kit, I'm pretty sure I understand both ways.

Just curious when your bleeding the brakes, old fashioned way, how many pumps do you need? 2-3? then tell the person to hold it down until you say its clear?


2 or 3 is fine, then hold down while you open and close the bleeder. Then tell the helper to pump two or three more times. Eventually, the helper will start to feel a firmer "pedal" as the air is purged from the system. The pedal will drop when you open the bleeder and the helper should push it to the floor when it does.

After a while you develop a rhythm. This is particularly good for developing and testing a strong relationship with your spouse or SO. If your relationship is still together after you bleed brakes it will be stronger. If your spouse or SO volunteers for a second brake bleeding experience you know you've found the right person.
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