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My first time brake bleeding - a few questions.
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Radrick123
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PostPosted: Fri Apr 13, 2018 7:52 pm    Post subject: My first time brake bleeding - a few questions. Reply with quote

I have a '76 Bay Window and a leak in the rear passenger cylinder so I will be replacing the cylinder, shoes and bleeding the brakes.

Is one of the $20 vacuum bleeding kits OK? Or should I get a friend to pump the brakes?

How much brake fluid do I need? What brand? And would you suggest DOT 4 or 5?

Thanks!
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aeromech
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PostPosted: Fri Apr 13, 2018 7:57 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Itís DOT 3 or 4. DOT 5 will screw up your brakes.

Use a friend to pump the brakes. My bleeder is $150 and Iíd never use anything else.
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PostPosted: Fri Apr 13, 2018 8:59 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

I donít like the vacuum bleeders on a bus. Iíve always had better success with the pump method.
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aeromech
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PostPosted: Fri Apr 13, 2018 9:47 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

I never had any luck with a handheld Mityvac but my Vacula can suck the chrome, well you understand
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Wildthings
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PostPosted: Fri Apr 13, 2018 11:39 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Buy a quart of brake fluid, you will probably not use it all, but may use more than one of the smaller bottles.
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stwesty
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PostPosted: Sat Apr 14, 2018 8:25 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

I've tried various one person bleeding contraptions including the Mityvac and all of them are an exercise in frustration. Get a helper to pump the brakes.

The only type I haven't tried are the pump style ones like this: https://www.amazon.com/Motive-Products-European-Bleeder-Adapter/dp/B0002KM5L0

But given the price and the space it'll take up I'm inclined to stick with a friend and a can of beer.
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PostPosted: Sat Apr 14, 2018 9:29 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

stwesty wrote:
I've tried various one person bleeding contraptions including the Mityvac and all of them are an exercise in frustration. Get a helper to pump the brakes.

The only type I haven't tried are the pump style ones like this: https://www.amazon.com/Motive-Products-European-Bleeder-Adapter/dp/B0002KM5L0

But given the price and the space it'll take up I'm inclined to stick with a friend and a can of beer.


This is the one to get:
https://www.motiveproducts.com/products/air-cooled-vw-bleeder

Works flawlessly and you can buy adapters to fit any other car you may own when you want to flush your brakes for a fraction of what it would cost you to take it to a shop more than once.
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PostPosted: Sun Apr 15, 2018 6:52 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Make sure your friend knows what he is doing, it makes everything go a lot smoother. Many moons ago I had some help bleeding brakes, I could hear him pumping the pedal but after many attempts still no pressure, turns out he was pumping the clutch.
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Radrick123
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PostPosted: Thu Apr 26, 2018 5:10 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Maybe this is a stupid question but canít i do the pump method myself if I have a long enough bleed tube that reaches to the drivers seat?
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raygreenwood
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PostPosted: Thu Apr 26, 2018 7:38 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Radrick123 wrote:
Maybe this is a stupid question but canít i do the pump method myself if I have a long enough bleed tube that reaches to the drivers seat?


Yes.....you can.....but there is a bit to it. I do all my brake bleeding without help.

1. The BEST.....BEST...BEST accessory money can buy is to get a set of "Speed bleeder" brand (not those crappy parts from Earls) brake bleeder check valves.....whether you eo it yourself or with help.

Nearly 9 out of 10 calipers and wheel cylinders from cars of our era leak air back past the bleeder screw threads on the return stroke of the master cylinder.
The speed bleeders have a very nice thread sealant that keeps this from happening. You can do this without speed bleeders by pulling the bleeder screw out and carefully and cleanly putting a small amount of teflon tape....on the threads only.

But....the hassle with that is that you really should remove it when you are done and pulling the bleeder valve back out can sometimes get a bubble of air back inside.

2. Quit opening the bleeder valves so far. Open them 1/4 turn or slightly less. Just "crack" them open. What far too many do not realize....is that when you have had the master cylinder totally dry.....unless the bleeding hole is very small....the cylinder cannot build pressure on the push stroke. Excessively low line pressure during bleeding can cause fluid to bypass air bubbles in high spots.

3.again when the master cylinder was dry or new.....for the first round of bleeding...push in fast....and let the pedal return very slow. At this early stage.....when there is not much fluid and lots of air in the MC....Rapid return strokes will not allow the compensating flap valves to open and admit air. It just shuttles air back and forth in the MC. A alow return stroke allows fluid to flow around the edges of the cups which do not yet have full inflation to seal.

4. Make a padded rod or crutch to hold the pedal to the floor against the front seat....while you get out to close the bleeder valve.

So crack the bleeder valve open very slightly.....give a rapid stroke.....slow release ....like 4-5 seconds. Do this 10 times. Push the pedal down and put the holding rod on it.

Get out, close the valve, check the fluid in the bottle, refill the reservoir and switch to the next wheel.

As the MC starts making better pressure.....you will feel both the benefits of the check valves in the speed bleeder screws and the use of a small opening setting taking effect. You should be able to build moderatley high pedal pressure and have it go to the floor slowly....like about 2-3 seconds due to the small opening setting.

It builds high enough pressure that you can hear the air "crackling" out through the bleeder screw check valve. Ray
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Spike0180
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PostPosted: Thu Apr 26, 2018 7:43 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Radrick123 wrote:
Maybe this is a stupid question but canít i do the pump method myself if I have a long enough bleed tube that reaches to the drivers seat?


You don't even have to have it reach the drivers seat. Just long enough to be able to submerged into a bottle on the ground by the brakes. Or maybe on a milk crate next to that wheel to put it above the brake bleeder, but as long as it goes above the bleeder at some point you should be ok.

-Take a bottle with some brake fluid in it.
-Take a piece of hose and make sure you get a tight fit around your bleeder screw (a hose clamp can be used if you feel the need).
-Place the end of the tube into the brake fluid, and make sure you have the hose go up above the bleeder screw before going down into the bottle (important to try to catch bubbles and prevent the bubbles from just going right back into your brake system.)
-Now, crack your bleeder screw and go pump your brakes for a while, making sure to keep the fluid in the reservoir full as always (make sure you pump for more time than expected is required, because you don't want to have to go back through the procedure). *If you have a buddy, they can verify that there are no longer bubbles coming through the system and into the bottle*
-Go back, shut your bleeder screw and remove the hose. (be careful not to spill brake fluid out of the hose)
-Move onto next required brake until you have gone through all 4 brakes.
-Make sure you set your star adjusters and set your E-Brake cables.
-Make sure you test your brakes before use.
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Last edited by Spike0180 on Thu Apr 26, 2018 7:57 am; edited 1 time in total
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Wildthings
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PostPosted: Thu Apr 26, 2018 7:54 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Spike0180 wrote:
Radrick123 wrote:
Maybe this is a stupid question but canít i do the pump method myself if I have a long enough bleed tube that reaches to the drivers seat?


You don't even have to have it reach the drivers seat. Just long enough to be able to submerged into a bottle on the ground by the brakes.

-Take a bottle with some brake fluid in it.
-Take a piece of hose and make sure you get a tight fit around your bleeder screw (a hose clamp can be used if you feel the need).
-Place the end of the tube into the brake fluid, and make sure you have the hose go up above the bleeder screw before going down into the bottle (important to try to catch bubbles and prevent the bubbles from just going right back into your brake system.)
-Now, crack your bleeder screw and go pump your brakes for a while, making sure to keep the fluid in the reservoir full as always (make sure you pump for more time than expected is required, because you don't want to have to go back through the procedure). *If you have a buddy, they can verify that there are no longer bubbles coming through the system and into the bottle*
-Go back, shut your bleeder screw and remove the hose. (be careful not to spill brake fluid out of the hose)
-Move onto next required brake until you have gone through all 4 brakes.
-Make sure you set your star adjusters and set your E-Brake cables.
-Make sure you test your brakes before use.


Wrapping the threads of the bleeder screw with teflon tape can help. One also doesn't need to crack the bleeder very far.
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PostPosted: Thu Apr 26, 2018 4:31 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

^^^^^^wrap the bleeders in teflon, & do a gravity bleed.^^^^^^^^^
One person operation. Has to be tutorial on the Samba somewhere.
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PostPosted: Fri Apr 27, 2018 3:53 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Iíve never owned a pressure bleeder and bleed them solo.

You donít need to put the hose under brake fluid, just route it up and then down so it has a head in it from the hose.

If air leaks into the bleeder itís either too loose or itís toast, out a new one on. I always have four new ones in my hand when I do brakes so that they never freeze. My cars typically go five years between major brake jobs so I put new bleeders on then.

If air is sneaking in between the hose and bleeder it isnít tight enough. Put a small clamp on it.

I flush with the bleeders wide open, until clean fluid comes out, then close , pump 10x, then just crack (1/8 turn or less) then apply slow strokes to push air out.

Road test for action and sponginess.
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PostPosted: Fri Apr 27, 2018 4:23 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

Wildthings wrote:
Spike0180 wrote:
Radrick123 wrote:
Maybe this is a stupid question but canít i do the pump method myself if I have a long enough bleed tube that reaches to the drivers seat?


You don't even have to have it reach the drivers seat. Just long enough to be able to submerged into a bottle on the ground by the brakes.

-Take a bottle with some brake fluid in it.
-Take a piece of hose and make sure you get a tight fit around your bleeder screw (a hose clamp can be used if you feel the need).
-Place the end of the tube into the brake fluid, and make sure you have the hose go up above the bleeder screw before going down into the bottle (important to try to catch bubbles and prevent the bubbles from just going right back into your brake system.)
-Now, crack your bleeder screw and go pump your brakes for a while, making sure to keep the fluid in the reservoir full as always (make sure you pump for more time than expected is required, because you don't want to have to go back through the procedure). *If you have a buddy, they can verify that there are no longer bubbles coming through the system and into the bottle*
-Go back, shut your bleeder screw and remove the hose. (be careful not to spill brake fluid out of the hose)
-Move onto next required brake until you have gone through all 4 brakes.
-Make sure you set your star adjusters and set your E-Brake cables.
-Make sure you test your brakes before use.


Wrapping the threads of the bleeder screw with teflon tape can help. One also doesn't need to crack the bleeder very far.


I use a smear of grease around the threads when bleeding. Works great. Use a Mighty Vac pump as well.
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PostPosted: Fri Apr 27, 2018 9:21 am    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

If you are pumping the pedal, just be careful and don't make the mistake I made (twice Embarassed ): If you have an old master cylinder and pump it beyond its wear-in limits, which is all too easy to do when bleeding, you will force the rubber seals into the crappy area of the cylinder and tear them up. Then you get to rebuild or replace the master cylinder, too!
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PostPosted: Fri Apr 27, 2018 12:27 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

jtauxe wrote:
If you are pumping the pedal, just be careful and don't make the mistake I made (twice Embarassed ): If you have an old master cylinder and pump it beyond its wear-in limits, which is all too easy to do when bleeding, you will force the rubber seals into the crappy area of the cylinder and tear them up. Then you get to rebuild or replace the master cylinder, too!


There are no "wear in" limits. The pistons NEVER contact the bore. They are undersized by a rather large amount. Only the cups contact the bore. The bore of master cylinders NEVER wear...unless you get rust or grit in them.

What you ran into...is rust/corrosion ring on the bore. This is caused by a combination of two things:
1, the hygroscopic (absorbs water) nature of brake fluid...and...
2. Not changing the brake fluid out for eons.

It gets saturated with moisture and forms an emulsion/goo. You can see this especially under the seal cups and flap valves and at some point this whitish yellowish goo will actually clog the compensation ports.

The cup seals will push this now unsolvable goo to the edge of the stroke. Being for the large part made of water and being stuck to the bore....it causes rust rings just past where the cups reach to during "normal" driving.

Bear in mind....that range of motion is just from normal driving. On panic stops and with extension from wear of pads....the cylinder pistons will always at some point(s) in their life... need to go into these farther down the bore areas. They are a normal part of the maximum stroke.

The cups and pressures do not set the stroke length. The stop pins under both the inner and outer spring are responsible for that.

If you have these rust rings....you dont "get" to rebuild the master cylinder....you "NEED" to rebuild your master cylinder because its JUNK.

The master cylinder should always be able to make its full bore stroke allowed by the stop pins (not the rust ridges that should not be there)....why?....because of what I already mentioned:

A. stroke length changes due to pad and e-brake cable wear and
B.....more importantly...if a wheel cylinder in one circuit fails...your stroke length will automatically increase as that circuit goes dead and all the braking falls to the other circuit.

Don't drive around allowing your braking to be limited to what rust rings that should not be there....allow you to have.

You can prevent them by bleeding the brakes on a regular basis. I am still trying to find the article from years back....I think it was in European car magazine. They did an EXCELLENT test piece with the basic bench mark Castrol LMA fluid.
They opened a fresh bottle....check moisture when new, did a wet and dry boiling point test...and then divided teh quart up into sections and measured the moisture absorption just when standing open to the air over a period of time....and then did moisture content and wet and dry boiling point tests on each....and corrosion testing with each batch.

The gist in a nutshell was that in a non sealed system (like ours)...within 6 months....the fluid while still fully functional had absorbed enough moisture to drop at least 30% of its wet boiling point. And...within 8-12 months...it absorbs enough moisture to be a rust hazard.

You get a little longer in our cars because the surface area exposed to air with moisture in it is low....but not much more.

Change your brake fluid out every 1.5 years and your master cylinder will last virtually forever. No rust rings...no limits on piston travel. Ray
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PostPosted: Fri Apr 27, 2018 1:23 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

raygreenwood wrote:
jtauxe wrote:
If you are pumping the pedal, just be careful and don't make the mistake I made (twice Embarassed ): If you have an old master cylinder and pump it beyond its wear-in limits, which is all too easy to do when bleeding, you will force the rubber seals into the crappy area of the cylinder and tear them up. Then you get to rebuild or replace the master cylinder, too!

<snip>
What you ran into...is rust/corrosion ring on the bore. This is caused by a combination of two things:
1, the hygroscopic (absorbs water) nature of brake fluid...and...
2. Not changing the brake fluid out for eons.
<snip>

Sounds about right. OK, so these are not really wear limits, but crappy parts of the cylinder walls nonetheless. The buses I have been working on lately have been sitting -- actually just sitting -- for 10 to 20 years. They got new master cylinders and booster rebuilds. I would never let my own vehicles go that long without attention.
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raygreenwood
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PostPosted: Fri Apr 27, 2018 2:05 pm    Post subject: Re: My first time brake bleeding - a few questions. Reply with quote

jtauxe wrote:
raygreenwood wrote:
jtauxe wrote:
If you are pumping the pedal, just be careful and don't make the mistake I made (twice Embarassed ): If you have an old master cylinder and pump it beyond its wear-in limits, which is all too easy to do when bleeding, you will force the rubber seals into the crappy area of the cylinder and tear them up. Then you get to rebuild or replace the master cylinder, too!

<snip>
What you ran into...is rust/corrosion ring on the bore. This is caused by a combination of two things:
1, the hygroscopic (absorbs water) nature of brake fluid...and...
2. Not changing the brake fluid out for eons.
<snip>

Sounds about right. OK, so these are not really wear limits, but crappy parts of the cylinder walls nonetheless. The buses I have been working on lately have been sitting -- actually just sitting -- for 10 to 20 years. They got new master cylinders and booster rebuilds. I would never let my own vehicles go that long without attention.


Yup...fully agree. The sitting still...KILLS these things. Really....if we can properly care for these master cylinders and keep the fluid fresh enough to never let rust form...the master cylinder casting and pistons will last forever and can just have new seals and flap valves installed every 5-8 years. Ray
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