Graham Man Posted February 15, 2022 Share Posted February 15, 2022 OK maybe I am crazy? I was at a truck alignment shop....about 30 years ago. I had my 1972 Mustang in for alignment. I had mentioned the brakes felt a little spongy, he said lets check it. He removed the master cylinder cover and placed a cast cover of sorts on the master cylinder and connected line air to it (125psi?) and then bled the brakes. Best bleed job ever. Has anyone seen one of these adaptors for bleeding the brakes? Is there something inherently wrong using this high of pressure? Link to comment Share on other sites More sharing options...
ply33 Posted February 15, 2022 Share Posted February 15, 2022 I haven’t heard of using high pressure air in a pressure bleeder but I have heard of pressure bleeders. In fact I made one for myself using an on sale garden sprayer and miscellaneous fittings purchased from auto supply and hardware stores. I made my own for two reasons: The commercial ones were more expensive than I could make myself. And second, I had to make my own adapter regardless as my early 1930s master cylinder is quite different than modern ones and the adapters that come with the commercial pressure bleeders would not work on it. Here are some commercial versions: https://www.amazon.com/s?k=brake+pressure+bleeder If you are using DOT5 brake fluid you will want to be careful in the design and use of a pressure bleeder so that you don’t agitate the fluid too much as it entrains small bubbles pretty easily. With respect to how much pressure to apply to a pressure bleeder, I suppose it depends on the design of the bleeder and how good a seal it makes on the master cylinder. It could be that the device you saw had a built in pressure regulator. On my home made setup I find 15 to 20 psi is all I need. Your car could be different. Finally, the reason I actually built a pressure bleeder was I was having trouble getting a firm pedal regardless of how much fluid I pumped through. That and that I usually work on the car by myself and traditional brake bleeding is a two person job. With my home made pressure bleeder the job became very quick and very easy and the pedal firmness got up to snuff. Link to comment Share on other sites More sharing options...
joe_padavano Posted February 15, 2022 Share Posted February 15, 2022 There are both pressure bleeders and vacuum bleeders. I have one of the latter. Best tool I've ever bought. The vacuum bleeder uses shop air through a venturi to create vacuum that sucks the air and fluid out of the bleeder screw. The key advantage is that you maintain a vacuum on the bleeder at all times, so there is no risk of sucking air back in the brake system when you pump the pedal. Link to comment Share on other sites More sharing options...
Graham Man Posted February 15, 2022 Author Share Posted February 15, 2022 (edited) I like the idea of pressure vs vacuum, but both have the same problem if you run low on fluid. Your shop air vacuumed solves the possible air leak at the bleeder. Curious if pressure vs vacuum removes bubbles faster? You would think pressure would make the bubbles smaller? Like the look of this one...no pump ($70). The little bottle is supposed to be a refill bottle so your reservoir will not go dry... I did find this unit, you are correct the plate could easily have a pressure regulator. the VACULA unit is $500 Edited February 15, 2022 by Graham Man (see edit history) Link to comment Share on other sites More sharing options...
TerryB Posted February 15, 2022 Share Posted February 15, 2022 I’ve seen the shop air pressure bleeder in use at a garage that works on old cars. I think it was a Wagner-Lockheed unit. The pressure was applied to the master cylinder using a cover that mimicked the master cylinder lid. Link to comment Share on other sites More sharing options...
JACK M Posted February 15, 2022 Share Posted February 15, 2022 I have used both pressure and vacuum. Preferred the pressure, although tough to get on to some M/Cs. And no, you shouldn't use high pressures. Might work but is quite messy. Problem with vacuum is that air will pull thru the threads in the bleeder screws, and it may always look like you are pulling air out of the system. I put some thread tape on those threads, and it helped. 1 Link to comment Share on other sites More sharing options...
joe_padavano Posted February 15, 2022 Share Posted February 15, 2022 (edited) 42 minutes ago, Graham Man said: Like the look of this one...no pump ($70). The little bottle is supposed to be a refill bottle so your reservoir will not go dry... I did find this unit, you are correct the plate could easily have a pressure regulator. the VACULA unit is $500 I got my Vacula for $15 at a swap meet. No one there knew what it was (including apparently the seller...). Your photo is an exact clone of mine. There are a number of similar Chinesium units out there, including ones from Harbor Freight. They all work exactly the same. And frankly, you'd have to be completely oblivious to the world to suck the reservoir dry. I don't have and don't need the refill bottle. I guess it's handy if you have the car up on a lift and don't want to raise and lower it periodically, but for normal garage use with the car on stands, it's not needed. Edited February 15, 2022 by joe_padavano (see edit history) Link to comment Share on other sites More sharing options...
Ltc4748 Posted February 15, 2022 Share Posted February 15, 2022 I have both the pressure type, 20 - 40 PSI max and a vacuum bleeder setup. I use the vacuum unit the most, it has a bottle made to add more fluid so the master does not run empty. As for the air leakage past the bleeder I use the thickest bottle of antiseize past on the threads, It reduces the air drawn past the threads, sometimes completely. The other benefit is the bleeder will still open 20 years later with no problem. Since you are bleeding the brake I remove the bleeder completely, dry the threads on it and put a thick coating on the threads and put it back in. Link to comment Share on other sites More sharing options...
joe_padavano Posted February 15, 2022 Share Posted February 15, 2022 (edited) 30 minutes ago, Ltc4748 said: I have both the pressure type, 20 - 40 PSI max and a vacuum bleeder setup. I use the vacuum unit the most, it has a bottle made to add more fluid so the master does not run empty. As for the air leakage past the bleeder I use the thickest bottle of antiseize past on the threads, It reduces the air drawn past the threads, sometimes completely. The other benefit is the bleeder will still open 20 years later with no problem. Since you are bleeding the brake I remove the bleeder completely, dry the threads on it and put a thick coating on the threads and put it back in. People worry about air drawn past the bleeder threads, but the reality is that it is irrelevant. The vacuum bleeder is lower pressure than the brake system. The air that leaks past the threads immediately goes into the vacuum bleeder. It can't get into the brake system. Yeah, you'll always see bubbles in the clear line from the bleeder screw to the vacuum bleeder, but who cares? With a little practice, you can hear the difference when all the air is out of the brake system. Just close the bleeder while the vacuum is still on and you'll be fine. I've been using mine this way for about two decades now. Note that anti-seize on the bleeder screw threads is always a good idea, and I add it as a matter of course, along with a dab on all the flare nut threads in the system. Edited February 15, 2022 by joe_padavano (see edit history) 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted February 16, 2022 Share Posted February 16, 2022 1 hour ago, joe_padavano said: People worry about air drawn past the bleeder threads, but the reality is that it is irrelevant. I see you have not used a Mighty-Vac on the newer bleeder screws with poor threads! I use PTFE tape or Never-Seize all the time on the new stuff. 50 year old bleeders (if they did come out) no issue. Link to comment Share on other sites More sharing options...
Ltc4748 Posted February 16, 2022 Share Posted February 16, 2022 I try to eliminate the air coming past the threads so I know when the lines are clear of air, it keeps me from bleeding too long and running the master dry. I want to avoid starting over 1 Link to comment Share on other sites More sharing options...
Graham Man Posted February 16, 2022 Author Share Posted February 16, 2022 (edited) Ordered one of these today. $62 on Amazon, $64 on Ebay. Thank you for all your input, let you know how it works. Found a nice video, looked good but needs a real compressor for air, almost like sand blasting. Edited February 16, 2022 by Graham Man update (see edit history) Link to comment Share on other sites More sharing options...
joe_padavano Posted February 16, 2022 Share Posted February 16, 2022 13 hours ago, Frank DuVal said: I see you have not used a Mighty-Vac on the newer bleeder screws with poor threads! I use PTFE tape or Never-Seize all the time on the new stuff. 50 year old bleeders (if they did come out) no issue. Mighty-Vac bleeders suck, or more correctly, DON'T. Every time you release the handle to pump, air gets sucked in. The vacuum bleeders that operate on compressed air provide CONTINUOUS suction, so there is no way for air to get into the brake system. The air bubbles are at atmospheric and will flow towards the lower pressure in the vacuum bleeder. That's physics. I've tried a Mighty Vac and thrown it away. That's why I use the Vacula that I have. Link to comment Share on other sites More sharing options...
Frank DuVal Posted February 16, 2022 Share Posted February 16, 2022 (edited) 3 hours ago, joe_padavano said: Mighty-Vac bleeders suck, or more correctly, DON'T. Every time you release the handle to pump, air gets sucked in. Not my experience! The check valve functions fine. Dial gauge does not move between pumps. I can get down to near -28 inches with a few hand strokes and that can suck a good portion of the container with brake fluid before getting back to nominal air pressure. Then a few more strokes and time to check the reservoir. I've had this Mighty-Vac for near 40 years.👍 I understand the other systems work better. Edited February 16, 2022 by Frank DuVal (see edit history) Link to comment Share on other sites More sharing options...
TerryB Posted February 16, 2022 Share Posted February 16, 2022 From a 1966 Wagner-Lockheed brake catalog. It was this device I saw used by a garage that works on old cars. Link to comment Share on other sites More sharing options...
Ltc4748 Posted February 16, 2022 Share Posted February 16, 2022 The pressure bleeder type must have a perfectly sealing master adapter so it hold the pressure from leaking off at the master. When they leak at the master cover adapter the air in the reservoir slowly disappears and then the brake fluid begins coming out since the master is now completely toppled off on fluid. DOT #3 fluid is not good for any paint or clear coat it comes in contact with, depending on how much time it is on and type of finish it can appear dull immediately and peel or blister in the future. There are very few adapters available to fit newer vehicles. You can get adapters to fit the older vehicles but not for all types. Link to comment Share on other sites More sharing options...
m-mman Posted February 17, 2022 Share Posted February 17, 2022 The Fluid Balls were the standard when I started 40+ years ago. They worked well but they were not for home or casual use. The ball was filled with maybe a gallon of fluid and could experience atmospheric exposure between uses. If you were bleeding several cars in a shop all day long that setup was fine, but a gallon of brake fluid was never cheap and if not kept in a 100% sealed container the humidity/moisture would be readily absorbed and lower the boiling point Link to comment Share on other sites More sharing options...
c49er Posted February 19, 2022 Share Posted February 19, 2022 Those Fluid Ball bleeders also had a diaphram separating the brake fluid from the pressured air to keep any air out of the fluid. The diaphrams failed but the bleeder still operate...now possibly with some air/moisture in it. Link to comment Share on other sites More sharing options...
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