I've only bled brakes using the old fashioned method.

I was at Harbor Freight and saw a little bottle with a hose that lets you do one-man bleeds.
http://www.harborfreight.com/automot...kit-37201.html

Even better, for $24.00 they have this reservoir that sits on your master cylinder and a air-powered bleeder that sucks the fluid from the bleeder.
http://www.harborfreight.com/automot...der-92924.html

My questions are -
1. Can you bleed the brakes with the master resevoir unsealed? That bottle just sits upside down with the nozzle submerged in the fluid; There is no seal.
2. Is it safe to suck out the fluid from the bleed valve? I've read that when using power bleeders that put pressure in from the master cylinder side, you should only use 20psi; this unit requires 90-120psi but is sucking from the bleed valve instead of pressurizing the master cylinder. Is this ok?

 

I've used a Mity-Vac to solo bleed brakes - it's slow going, but works ok. 90-120 psi seems a bit high. IIRC I pump it up to 60-80 and at higher pressures tend to get air bubbles sucked it from the seal/nipple interface. I can't see that more 'suck' would damage anything.
Recently I just cajole the wifie into coming out to do the old fashioned "up - up, down - down" system.
I've also used a tube/bottle combo which lets you pump it yourself. In practice I think it works fine, but it's nice to have a visual at the bleeder valve to check for air bubbles.

 

20 PSI is what I use on my motive pressure bleeder. Works great, love that thing....

Only issue with a vacuum system is it's easier to get air in the lines than with a pressure bleeder. I'd either use a pressure bleeder or do it the old fashioned way...

 

+1 for the Motive, it rocks...

 

I think the the 20 psi limit on the motive is to avoid damaging the fluid reservoir. So, higher suction at the bleeder shouldn't affect the reservoir.

 

When using brake bleeders, you want to use the pressure bleeders that 'blow' and not the ones that 'suck' (don't any of you dare say 'that's what she said'). The pump-at-the-reservoir style is pretty fool-proof, whereas the ones that use a compressed air vacuum, can actually leave a couple of bubbles in the caliper at the bleeder valve. If you already have the vacuum style bleeder, not to worry: you can always finish the job at each corner with an assistant pumping the brake once or twice.

 

I prefer the pressure bleeding style too. I built my own version of the Motive bleeder system for about $15 using a master cylinder cap from O'Reilly's, some hardware store tubing, and a cheap garden sprayer bottle. I found instructions on-line at:
http://www.bmw-m.net/TechProc/bleeder.htm
Works great!

 

I stopped by my tech's shop to pick up some parts yesterday and his buddy sold me a used pressure bleeder and catch bottle from bavarian autosport for $15! Score!

 

If it works, then it works. Don't have any experience with it, though. However.......

Any brake bleeding tool that forces fluid into/through the system using air pressure is a huge nasty no-no UNLESS that tool is designed to keep the pressurized air from direct contact with the fluid. It's a fact that the cheap pressurizing systems have direct air to fluid contact and all that does is put micro bubbles of air into the fluid. There MUST be a diaphram or bladder or piston or some means to separate the pressurized air from the fluid itself.

 

'Just checked out the Motive pressure bleeder. Bad idea. Same with home made bleeders made form sprayers and the like. Like I said, any cheap system that doesn't isolate the pressurized air from the fluid is going to put air in the fluid. Period. End of story.

 

Thing is, you're going to need quite a bit of pressure to get those microbubbles. I seriously doubt using the Motive on low pressure--the lowest amount that will push the fluid through (I can usually flush at 10 PSI or lower--I like to keep the pressure low anyway)--is going to cause an issue. People have been using them at the track for years...

Otherwise, you're looking at 300 bucks for a bladder system.

The old, manual way is still probably the best--but there can some issues too with that if not done correctly.

 

From the StopTech site:

...........Second and more serious (after all you could supply it yourself) all dealerships and most independent mechanics use pressure bleeders. These devices certainly speed up the process of brake bleeding, but by forcing the fluid through tiny orifices using pressurized air, any air left in the partially filled system will be forced into the fluid solution. Quadruple Damn!!!!

Pressure bleeding do's and don'ts

Pressure bleeding on its own is not necessarily a bad thing, but there are several steps one must take to ensure that the bleed event will result in an air-free brake system.
When we talk about pressure bleeding, we are referring to the process in which we pour our brake fluid into a pressure vessel, hook up a pressure source, and run the now pressurized fluid directly into the master cylinder reservoir. One by one the caliper bleeder screws are opened to allow the pressurized fluid to flow through the system until all of the old fluid has been purged. Simple, right?
Well yes, but beware of imitations – not all pressure bleeders are created equal. The professional units (the type you can consider using) separate the pressurized brake fluid from the pressure source (air) using a flexible rubber diaphragm. In this fashion, the pressurized air is kept from forcing its way into the fluid. As we all know, air and fluid should be kept as far apart as possible.
This brings us to the imitations. There seem to be a rash of products available lately that claim to be pressure brake bleeders at a fraction of the cost of the professional units. Like most things that sound too good to be true, well, it’s exactly that.
Like the professional units, these imitations contain a pressure vessel into which new brake fluid is poured. However, in order to pressurize the fluid, an integral pump handle is cycled to build the pressure inside the vessel without any measures taken to separate the pressurized air from the fluid. For those of you who have ever bought a $19.95 do-it-yourself potted plant and bug sprayer from Home Depot you get the idea.
Of course, having pressurized air in contact with the brake fluid will certainly force the fluid through the system just as effectively as the high-zoot professional unit, but as an added bonus we are stuffing air into the brake fluid at the same time. Talk about an unwanted surprise!
While it may not be visible to the naked eye (air can actually entrain itself in the fluid as to be visually undetectable) it’s there right along with all of the nasty moisture trapped inside of it. This of course begs the question: if you are stuffing air and water contaminated fluid into your brake system, why even bother bleeding it in the first place?
Naturally there will be those who argue that the amount of air in question is not important enough to worry about, but think about this for a moment: nearly every automotive manufacturer stores their bulk brake fluid in large containers which are subjected to a constant VACUUM. Talk about an expensive process! If just storing your fluid under regular atmospheric conditions isn’t good enough to keep air and water out, just imagine what shoving 30psi worth of compressed air on top of it is doing.

 

Well, that's like saying "Motoring increases your risk of dying by a car accident. Period. End of story." (So, motoring is a bad idea.)

The solubility of the air in the brake fluid (this is really the issue---we aren't blowing bubbles into the fluid like blowing bubbles in a straw)--- is going to depend primarily on the air temperature, humidity, and the pressure that the bleeding device is pumped to.

As CCT1 said, the pressures (I use ~10 psi as well) that these things create are unlikely to dissolve huge amounts of air into the brake fluid. If large amounts were being dissolved in the fluid, we should be seeing the fluid bubble after de-pressurizing the bleeder device (like opening a pop bottle).

For most folks, the Motive pressure bleeder doesn't cause any issues and the speed and convenience of one-person brake bleeding makes it worthwhile.

 

Well, to each their own, I suppose. I just don't like the idea of introducing any more air into the system than I have to. And I respect what StopTech has to say about the subject. They really know their stuff. ('Love to have a set of StopTech calipers and rotors on my Mini some day.)

 

I used to have a great little air pressure bleeder for my MGB. Had a remote reservoir, a cap that fit exactly over the master cylinder cap on the MG, and an air line you could hook up to a tire if you wanted to. The air came into the top of the remote reservoir, pushing the brake fluid down (and up through a long pick up tube) and into the master cylinder reservoir. Pressurized the whole brake system, all I had to do was crack bleed screws and make sure the brake fluid in the bottle didn't run out. No more "Pump it up....... hold it down....pump it up..... hold it down."

Here's how it works: http://www.sandsmuseum.com/cars/elis...kes/index.html