Either you’re being thick or we are talking about different things.
Many (not all) pressure bleeders will also allow you to pressurize the brake master cylinder reservoir without having feeding any fluid into it.
Vacuum Brake Bleeder Tip
- Thread starter The Critic
- Start date
Many (not all) pressure bleeders will also allow you to pressurize the brake master cylinder reservoir without having feeding any fluid into it.
edyvw
$50 site donor 2025
This one is not using air to pressurize the cylinder. It is using fluid. It sucks out air. This one, Schwaben, Motiv, etc. I so far have not stumbled on one that is using air.
So, in light of being thick, maybe you should, idk, use Google. It helps. You might stumble on this and help you resolve issues with pedal feel: https://www.ecstuning.com/b-schwaben-parts/3-liter-european-pressure-brake-bleeder/007237sch01a/
Last edited:
Hint: how is the fluid getting to 15 psi? Air. You are pumping up the unit to force pressurized fluid into the master cylinder reservoir.
edyvw
$50 site donor 2025
And, again, that is a problem bcs. somehow you force moisture into it? OK, I think you should contact manufacturers (and that is not only BMW) and explain to them that their practice is not good.
The funny thing, my moisture tester never shows a higher % of moisture. So, exactly, how much moisture we are talking about here? 1%? 2%? 3.49% (wet boiling point)? 0.0005%?
How much atmospheric moisture and air gets dissolved into the brake fluid when the tank is pressurized? That's an interesting physics question. I don't know the answer.
During a half hour bleeding/flushing session there seems to be negligible contamination of the brake fluid in the tank, with water or air bubbles. I have always had a firm pedal using the simple Motive pressure bleeder. But I would definitely not store the brake fluid in the Motive bleeder.
Last edited:
Pressure bleeder? Maybe on the newer screw on caps they work okay, but on the older wire clip caps they can leak and sometimes make a huge mess and spray fluid everywhere, been there done that. You know that brake fluid can remove paint! Main reason I just do the vacuum way now.
Oh and high quality pressure bleeders have a bladder to separate the air from the brake fluid, any others that don't do that are just cheap junk and a waste of time and money.
Oh and high quality pressure bleeders have a bladder to separate the air from the brake fluid, any others that don't do that are just cheap junk and a waste of time and money.
Did you read my entire reply in post #13? I specifically stated that OEM's prefer the diaphragm style bleeders or electric bleeders for this exact reason.
Since you have high regards for BMW's position, this is their exact statement on their dealer tool page:
https://www.bmwcentersolutions.com/equipment/product/18544
Someone copied and pasted GM's instructions for the C8 Corvette. They have a similar concern about exposing the fluid to outside air; they recommend the diaphragm style (Branick) bleeders:
https://www.corvetteforum.com/forum...c8-brake-bleed-discussion.html#post1601048665
Point is, OEM's do agree with you about pressure bleeding, but they do not consider your style of pressure bleeder to be acceptable.
Good question. Just posted a new thread about the Speedi-Bleeder - if that one is connected to a portable air tank with nitrofill snake oil, I wonder if that would be a happy medium.
Agreed. And @edyvw doesn't seem (or want to) understand that.
These two things from Harbor Freight work great to vacuum bleed brakes. Just need a hose barb to connect to the vacuum pump if none of the adapters in the brake bleeder kit will fit it:
https://www.harborfreight.com/air-v...connectors-96677.html?_br_psugg_q=vacuum+pump
https://www.harborfreight.com/brake...t-63391.html?_br_psugg_q=brake+bleeding+tools
edyvw
$50 site donor 2025
BMW in ISTA does not indicate the type of bleeder.
Also, exposure to outside air is NOT the same as what you argue, that due to pressure built by air somehow moisture is penetrating into the fluid at a higher rate. You are exposing fluid to the outside air by doing a vacuum too. That bleeder (that BMW has) has much higher capacity. I would say their concern is not what builds pressure, but the storage of fluid in the pressure bleeder at a prolonged period of time. I agree that the average dealership would like a hermetically separated bleeder. But that is not a concern when you pour fluid into the bleeder 5 minutes before doing work!
I very well understand exposure to outside air. Concern in a dealership is long-term exposure to air as a reservoir is of much higher capacity. I would not like having fluid in bleeder I have just sitting waiting next flush. But, for small shops, or DIY, type of bleeer I have is perfectly fine as when I flush brakes, that is when I open the brake fluid container.
Also, you are quoting people switching DOT4 fluid and SRF fluid constantly, which is a recipe for disaster, and would not look for them to give any advice.
Last edited:
I use the pressure bleeder in the cold dry air of November or December thus reducing the moisture in the air
edyvw
$50 site donor 2025
All this exercise is based on nothing more then assumption. Having brake fluid in some type of bleeder reservoir that has a capacity of hypothetically 5 gallons and air inside, is a problem as that is designed for dealerships, buying bulk fluid etc. Opening brake fluid bottle, pouring into air pressure bleeder is not a problem whatsoever, or it is a problem same as pouring brake fluid into master cylinder reservoir or doing vacuum bleed.
I was trying to find any evidence that this is an issue, and couldn’t find it. And then, how much moisture does get in having pressurized fluid for 30-45min?
I am not aware of any controlled study for this type of scenario. I think is an example of applying theoretical concepts to a situation.
I think this person explains the issue better than I can:
https://community.cartalk.com/t/thoughts-on-pressure-brake-bleeders/141691/11
edyvw
$50 site donor 2025
My moisture tester can’t register any change, which means you need far more precise tool. That begs the question: what practical impact does it have?
Air compressor tanks are what, 125PSI?
How many PSI is used in a pressure bleeder?
Seems to me that the amount of water that comes out of air when it's compressed is proportional to how much it's compressed.
How much water is there in a balloon? You blew up with air from your mouth? As much moisture as that has in it? I've never seen any.
How many PSI is used in a pressure bleeder?
Seems to me that the amount of water that comes out of air when it's compressed is proportional to how much it's compressed.
How much water is there in a balloon? You blew up with air from your mouth? As much moisture as that has in it? I've never seen any.
edyvw
$50 site donor 2025
Pressure bleeder should be set to 10-15psi.
Usually 15 psi for routine fluid changes, but this is starting to change. Some OEM's are requiring as much as 30 psi for ABS related bleeding events.
The balloon analogy makes sense. I'm sure if there was a way to accurately measure the moisture content inside of a balloon, it would be significantly higher than ambient.
Moisture content inside balloon would not be more than ambient but its relative humidity would be higher (not counting moisture picked up in lungs). The higher the pressure the higher RH.
