ndnchf
Well-known member
Why is that?
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Brake Bleeding
- Thread starter merlin1952
- Start date
Why is that?
atikovi
Well-known member
Pulling fluid out of the line via vacuum is the opposite of pushing it via pressure bleeding.
ndnchf
Well-known member
Pulling fluid out of the line via vacuum is the opposite of pushing it via pressure bleeding.
I understand that. But why do you need to start at the closest wheel rather than the farthest? I'm not trying to be difficult, just trying to understand the physics of it. A lot of people here have had great success with the vacuum bleeders and have not mentioned the need for this. I just bought a vacuum bleeder last week and will be using it on my old Willys jeep.
atikovi
Well-known member
Not exactly sure why but that's how I've done it with my vacuum bleeder for 15 years. Says in the manual https://www.lbusupport.com/asp/cd/pdfs/SECTION_MV15_PAGE_1_FLUID_E.pdf on page 5 section 2c.
ndnchf
Well-known member
Not exactly sure why but that's how I've done it with my vacuum bleeder for 15 years. Says in the manual https://www.lbusupport.com/asp/cd/pdfs/SECTION_MV15_PAGE_1_FLUID_E.pdf on page 5 section 2c.
Thanks - I see where it specifies closest first. I don't know if it really makes much difference where you start. But I'll give it a try. I'm always glad to learn something new.
GirchyGirchy
Well-known member
Anyway, if you people read the link, then you would not have made the above comments.
It is always a good idea to read BEFORE making comments.
Read it. I know what garbage collects in my filter & drier, so no thanks.
dbm52
Member
+1 on driftpin, ive used this on my bikes, boat trailer, cars no problems very inexpensive and simple
I like to see the fluid at the bleeder to confirm that all the bubbles are out. While the speed beeder valves definitely work, you can't pump and watch. It is back to 2 people or faith that you did a good job.. Call me paranoid.Speed bleeders are awesome for a one person brake bleed. I use them for my combo daily drivers / track car and will do a quick bleed before every track day whilst I'm changing tyres.
They are replacement bleed ******* that have a one-way ball valve and some thread sealing paste. You put a length of clear hose on the ****** to an old jar, open the bleed ****** a 1/4 turn, and then pump the pedal a few times. Close the ******.
http://www.speedbleeder.com
I have a pressue bleeder and would only use it to fill a system that was completely empty. To do a fluid change I'd use the speed bleeder. Faster and less clean up.
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Another vote for Motive. Easy peasy, never had an issue.
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I did. They tell you to pump the system up with air, first, to see if it holds pressure, no leaks. I had a terrible time pumping up air pressure, even though the pump was already lubed with brake fluid. Once I filled the tank with fluid it pumped right up to the desired 10-15 psi. Now I check for a tight seal, start with fluid and watch for leaks. What the Motive lacks is a pressure relief valve. You have to loosen the cap. The resason is they are using a modified garden sprayer and the pressure gauge is mounted where the sprayer had the pressure relief valve.
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Schurkey
Well-known member
Nope. Higher pressure in the reservoir, lower pressure at the wheel cylinder. Pressure difference causes fluid flow, which tends to drive out air pockets.Pulling fluid out of the line via vacuum is the opposite of pushing it via pressure bleeding.
It's exactly the same if using vacuum or pumping the pedal or pressure bleeding. Even gravity bleeding uses the same pressure differential, but there's less pressure so it takes longer.
Reverse-injection bleeding changes the pressure differential from higher pressure at the reservoir to higher pressure at the wheel cylinder...but Reverse Injection bleeding has problems of it's own.
Mac wants you to change the order the wheels are bled in, but really it doesn't make any difference at all. Do 'em in whatever order you want, as long as you get fresh fluid and no air by the time you're done.
I will be starting at the farthest from the master, and finishing with the closest to the master.
atikovi
Well-known member
Mac wants you to change the order the wheels are bled in, but really it doesn't make any difference at all. Do 'em in whatever order you want, as long as you get fresh fluid and no air by the time you're done.
I will be starting at the farthest from the master, and finishing with the closest to the master.
There has to be a reason why the tool manufacturer suggests that. Thought it has something to do with residual pressure check valves between front and rear. Might work differently when under vacuum than under pressure.
ndnchf
Well-known member
I looked at the manual for my HF Pneumatic brake bleeder. It says to follow the vehicle's service manual guidance. I know HF directions can sometimes be pretty crappy, but I think this is sound advice. If I recall correctly, the Willys CJ2A manual says bleed in this order: RR, RF, LR, LF. That makes sense to me.
Teflon tape around the thread, no grease.This....
The air that gets sucked in around the threads just goes right back into the vacuum bleeder. It does make it a little hard to tell when you have a good solid stream. But usually I just go by the color of the brake fluid. **** the first one until the fluid runs clean. The first one is usually the longest since you are emptying what's left in the master. I do **** out as much as I can in the master before starting to bleed to save a little time. Then **** the other 3 wheels til new fluid shows. This has always worked for me and gives a good pedal. Even when I have to replace calipers or other parts and have to bleed the whole system. Although thanks to another GJ member that shared his trick of pushing the pedal in 1/4 way before taking a caliper off will stop the fluid from bleeding out.
I have always wanted to find a grease that is compatible with brake fluid and just put a dab on the threads of the bleeders so I can see when the fluid runs clear with no bubbles. Would be more of an OCD thing for me since I know it isn't needed after doing many brake fluid exchanges now that most manufacturers recommend them every 2 years regardless of miles. But would still be nice to see a bubble free stream. Just haven't been able to get an answer on what grease to use that won't screw up the brake fluid. Someone told me dielectric but not sure.
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