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Mityvac for break fluid change


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The mityvac for me seemed more trouble then what its worth, its hard to get a good seal and so little air bubbles appear while trying to pump out the break fluid and it didn't seem to work very good since its hard to get enough suction. i did find it easy to use but not to work as well as doing it the old way, *using the break pedal*.

~Steven

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I agree that the Mityvac is not great for bleeding brakes or clutches. It is still worth buying one to do vacuum system checks. I consider it a must have tool.

 

There are instuctions around the web for building a power bleeder from a bug sprayer. You would have to do a lot of bleeding to make it worthwhile.

 

Use a baster or something to pull the old fluid out of the reservoir and replace it with new. Get someone to pump the pedal while you bleed. Bleed until you get clean fluid.

 

If you have ABS, never open a bleeder with the key on. After you bleed, go out on a dirt road and lock up the brakes a few times. Go home and bleed them again. Repeat until you get clean fluid.

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I have used the MightyVac method for bleeding my Subes' brakes several times and it has worked quite well. The secret to getting a good seal is you need some of that silicone goop (not RTV) to put around the bleeder; my vac kit came with a small tube of it. Then no air gets sucked in.

 

First I suck out most of the fluid in the MC, trying to move the suction tube around in there to get any dirt I see laying in there. Then I fill 'er up with fresh fluid. Then go to each wheel in the order specified in the manual. Then I pump the device a dozen times or so and while it's sucking the fluid, I slowly press the brake pedal up and down to the floor a couple times; this seems to get more grungy looking fluid out.

 

A couple things I learned were to keep an eye on the level in the cup that's sucking in the fluid because if it overflows, the brake fluid goes into the pump, which doesn't seem to harm the pump but it makes a mess. I used a small cardboard box with a hole cut in it to keep the cup upright; otherwise it tended to tip over and fluid got sucked into the pump.

 

Also if you have a Harbor Freight nearby, they have a red handled brass pump and cup setup for this purpose for less than half of what Sears charges for the exact same looking device (it's not a MightyVac though; it's just a cheap Chinese unit but it seems to work fine). I bought speed bleeders but haven't installed them yet; learned about them after I used this method. I like to bleed brakes in the ABS in the winter on a snowy day because then I can easily take it out on the snow and get the ABS pump to run. I like to try to run the ABS pump periodically anyway so it doesn't atrophy. :-) Louis

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Thanks for the info all. Not to:horse:but I think I am going to buy one and give it a try, if I am not happy I will go to speed bleeders.

Just a little more info though if you don't mind. Porcupine(?) mentions Teflon goop I think it is. Can you give me some more information on that? Is it like pipe dope plumbers use? Or is it more like Teflon tape? Also I know there will be an order of bleeding but any suggestions? Furthest from the master cylinder first? Closest first? Or does it not really matter? As always thanks

Joe

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Joe, howdy! The goop isn't pipe dope or anything like that. It is from what I remember it is silicone of some sort, kind of the consistency of Vaseline. It did not have Teflon in it. I lost the Sears thing that listed some Dow part #'s for it, but I used Dow high vacuum silicone from McMaster last time which seemed to work OK. The Sears instructions definitely said not to use anything other than the specified silicone as it might not be compatible with brake fluid. I'm guessing the speed bleeders are probably a lot easier to do and a lot less mess and you don't have to worry about what the silicone stuff is; I got speed bleeders from Summit Racing for $10 a pair I think.

 

I would check the Subaru service manual for the bleed order, and any specifics for the model such as ABS or whatever. From what I remember the Subaru manual order was the exact opposite of what the Sears instruction sheet said. -Louis :)

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I have read (here I think) of someone using a portion of bicycle inner tube to make a pressure bleeder. Cut out a section with the schrader valve, fold one end over enough to be able to secure and seal it air tight, stretch the open end over the MC reservoior and secure with a hose clamp/whatever to make an air tight seal, connect to schrader va;ve and pressure inflate the tube.

 

sounds like it would work - I dunno, haven't tried it myself.

 

Carl

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Yea,,, thanks there Tex but I think I am going to pass on the ole bicycle inner tube thing. Maybe it would work but not exactly my style. I am going to give the Mityvac a shot though. Thank you Porcupine, I think you've stuck a quill in my break bleeding situation. I'll report back.

Joe

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  • 2 weeks later...

I think that he was using a silicone-based grease, like a "vacuum grease" that would be used in an industrial or laboratory setting. And I have also found the mightyvac to be pretty useless (after paying $50 for it!), but I have not tried using a vacuum grease yet.

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Hi MSSLGECKO, no I used the Dow High Vacuum Silicone Grease shown below (bought from McMaster-Carr). I think it was like $10 for that tube which is like a toothpaste tube size enough for a lifetime I'd imagine.

 

The pump I bought (from Sears) came with a very small tube of stuff, but I used it up, and couldn't find any of the substitutes listed in the Sears documentation, so I tried the Dow stuff. It seemed to work fine; however, I do not know if it is recommended for use in brake applications. I definitely wouldn't use that Goop stuff as we're working with safety critical car brakes here, not a kitchen sink. :banana: :cool: Yes, then after I've closed the bleed valve when I'm done I wipe it off with a clean rag.

 

Anyway, you can get a fairly inexpensive such vacuum kit from Harbor Freight; you don't have to pay $$ for a name brand MightyVac. The setup I bought from Sears for $50 looks exactly the same to me as the one at HF for like $20 on sale.

 

I have had excellent results with the vacuum brake bleeding system. If you don't use the grease though, it does such mostly air bubbles around the bleeder. -Louis :)

 

dowvacgrease1.jpg

dowvacgrease2.jpg

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You can buy silicone grease from SCUBA shops or paintball shops. They use it on O-rings in high-pressure systems. A welding shop may have it, haven't ever tried them.

 

I will try the silicone grease next time I bleed brakes but I will have the ever trustworthy helper to pump the pedal also.

 

You could suck air through the threads on the bleeder as well as around the hose.

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  • 4 months later...
I got speed bleeders from Summit Racing for $10 a pair I think.

Did they have them for the model of your subi? I don't see any listing for my 01 LLBean :-/

Where else should I look for some quality speed bleeders? I am going up to the mountain, so hopefully the snow will be there so I could flush brakes+ABS properly :) But I would need to rush to get those speed bleeders to don't use m-vac since I don't have any vac greese to use

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Yep, Summit had speed bleeders in my size. I think the brand was Russell. I believe it was 10mm x some thread. I can't imagine it's much different from Suby model to model.

 

Anyway, I figure if someone is going to drop $50 on a mityvac they could just spring the extra $10-$15 to get a huge tube of silicone grease from a place such as McMaster. Or maybe the mityvac includes a small tube; the crapsman I bought included a pittance.

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I just bought a vacuum pump similar to a Mityvac. It takes a different frame of thought to use it in a manner that works well.

 

I applied some teflon tape to the thread areas just above the bleed hole. That way it is not an integral part of the brake fluid space - but it limits some of the air bubbling that comes with doing a vacuum bleed (as opposed to pressure bleed - pedal or otherwise).

 

Okay - on to the usage. It was a bit more work than I expected. But it worked fine for all four corners of my Cabriolet and the Legacy. The Cabriolet was considerably easier to do with the wheels on and the car on the ground. The Legacy was harder to reach the bleed screws the way they are oriented.

 

As everyone already noted, pulling all the old fluid out of the reservoir first is the best way to start. If needed, pull the grungy old reservoir off and clean it well with brake cleaner (or your choice of cleaner). Then refill it with clean fluid.

 

As you bleed the wheels, you WILL see a lot of bubbles from the threads. But if the color changes from brown to clear, you know the bleed is working. And if your master cylinder and ABS modules are fine, then that color change is a good indicator of a bled system. Pedal feel ultimately dictates the effectiveness of the bleed.

 

Remember to have the bleeder screw under vacuum at the moment you are closing the screw tight to prevent air re-entering the system.

 

And don't forget to top up the reservoir as you do this. It really bites if you bring in air from the top and significantly lengthens the time to re-bleed.

 

I went crazy-go-nuts and used a whole liter of fluid to do all four wheels. :brow:

 

So overall - give a vacuum bleeder a try (especially for the price if cheaper than Mityvac). If you hate it, then you still have an important diagnostic tool on-hand as well as a good backup bleeder. If you like it, then all's well that ends well.:)

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I have speed bleeders on my BMW and will probably add them to the subie when I change the fluid next.

Between those and keeping hoses submerged in a jar of brake fluid it makes one man bleeding pretty easy. A lot of folks swear by those pressure bleeders that go on the master cyl.

If I'm only doing it every few years speed bleeders seem cheap and easy. If I had a shop I'd do it with the master cyl type as it would pay for itself.

I used to use an electric fuel pump on trucks.

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Remember to have the bleeder screw under vacuum at the moment you are closing the screw tight to prevent air re-entering the system.

 

And don't forget to top up the reservoir as you do this. It really bites if you bring in air from the top and significantly lengthens the time to re-bleed.

Sounds good JPX! What you say is so true. I've found that if you have the bleeder open just a little but build up enough vacuum in the collection chamber, it gives you a chance to push the brake pedal slowly to the floor a few times. I've found sometimes I get some extra gunk out the system this way.

 

I think the vacuum method works great for changing the fluid by yourself. I usually do it once a year whilst changing from snow to summer tires.

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Yep, Summit had speed bleeders in my size. I think the brand was Russell. I believe it was 10mm x some thread. I can't imagine it's much different from Suby model to model.

Indeed they should not but ... I've sent an inquiry as directed on http://www.speedbleeder.com/automobile_applications.htm

Lets see how fast they reply ;-)

Do you know what chains sell them? I've heard that Pep boys have some other - Motormite I think

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I dislike my mityvac too. Its only handy as a vac pump for diagnostic IMO.

 

The ones for the Master cyl are really sweet but expensive.

 

A friend, some aquarium airline tubing and a jar is actually more effective if you ask me. Fish stores sell silicone airline tubing which fits nicer.

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