Can someone give me the "how-tos" on gravity bleeding brakes?! I plan on replacing a rear caliper (finally) on Friday, and would like to hear what its about...

Thanks

 

just fill up the master cylinder and loosen the bleeders (at the calipers) just enough to let the fluid slowly leak out. You dont want it pouring out or you'll run you master cylinder dry and have to start all over. It should basically be a good paced drip. I also recommend attaching a short length of hose to each bleeder. This serves two purposes: One, it allows you to direct the fluid into a container more easily, and Two, it ensure that no air creeps back into the bleeder. Gravity bleeding takes time but it's the best way. It wont wear out the master cylinder the way conventional bleeding does. If you've got the time and dont want to pay attention to it, you can do one or two calipers at a time (same order as you would with conventional bleeding). That way you dont' have to worry about the master cylinder going dry.

If you're in a hurry you can use vacuum to literally suck the fluid and air out of the lines. But make sure you have somebody with you to keep fluid in the master cylinder or you'll be doing this for a while. You can accomplish this with a simple hand held vacuum pump.

 

I've never heard of this method of brake bleeding before. It sounds so much easier than the tighten-untighten-one-at-a-time method. How come everyone doesn't do it this way? Is there a "catch"?

 

The only "Catch" is that you need something to "Catch" all the fluid dripping from four corners of your car. It is by far the best way to bleed the system and the least damaging as well. It's also a great way to bleed the clutch system.

 

How long does this process take?

 

Wow, well I did the process and it worked great. Wish I'd known about this some time ago! Took very little time, since the brake caliper had been gravity bleeding the whole time it was bad, and the other bled straight fluid. Took the car out after, and after "stomping" on the brakes, it adjusted (couple of quick "jolts"), then ran nice and tight. Nice to have good brakes again. It's been 3 months since the caliper had been leaking. BTW, got a good caliper from ZXMAN.COM . Good site for spare parts and great prices! Also got a pair of adjustable hood bumps ($12.50 for both), and a new idler pulley bearing ($10). Used Tokico caliper was $55. Overall, good experience...

Thanks to all...

 

i have used this method too but i never knew it was called gravity bleeding i just thought it was much much easier than haveing one of my sisters who are like 80lbs to help pump up the brakes then i would turn the little bleeder screw , i just had to buy 2 used rear calipers for my 280zxt and ill let yall know how long it takes me to change them out and be able to gravity bleed them nismo619

 

Ok, from what I can gather after doing it, the time spent bleeding all depends on how long the line is open, letting air replace fluid. I did both rears, and it only took roughly 10-15 minutes each to reach pure fluid. BTW, the brakes now are more solid than I've ever had them, and I have force bled them in the past, so this is obviously the best way! I wish I had heard of this method years ago...

Good Luck...

 

and your master cylinder will thank you too

 

update gravity bleeding DOES WORK GREAT forget about that 2 person pumping 3 times and releasing the valve .. dont do that any more let me tell u first hand no more having my friends or g.f. come over to help me work on my own brakes !! whoo hooo !!!! ill be gravity bleeding both my 300zx's next week

 

Strangely, in all my experience the brake fluid hardly ever comes out unless the system is fully bled already.

I tried this on my Z and then on my truck. Did not work at all. Nothing came out. I let a pair of calipers hang open for about 3 hours while I did other work. In all that time not one drop came out. I then did some work on another Z where a lot of the fluid came out of the front brake system. I got the brake suction hooked up and after a half hour could not get any fluid to even suck out! It keeps drawing air. I even filled up the pump with fluid so there's less room for air vaccuum. It keeps pulling air from around the threads of the bleeder. I just barely crack it open enough to release pressure and it'll still suck air at the bleeder rather than fluid from the master. I resorted to the old fashion way of pumping the brake pedal and the brakes were done in no time.

I'd rather bleed brakes by another method but gravity bleeding does not work.

 

You did it wrong

It does work... If you do it right, rookie

Seriously though, that is really weird. You must have just had more air in the system than fluid or something because every mechaninc I know swears by the gravity bleeding process. Maybe you just had dumb luck or something. I don't know what happened. I'll bet that right now, if you have a good feeling pedal, and you tried gravity bleeding it again that it would get even better. Try it and see

Rod.

 

I will try again... please forgive me, I'm new to these Z-cars and mechanics stuff

 

 

Ok, I figured it out. My brakes had quite a bit of air in them. If you're starting to bleed a system that has been drained you need to pump the pedal a lot before fluid seeps into the lines enought to bleed out on its own.

I got it going on the truck and Z.

 

Rock on!

 

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