Gravity Bleeding Brakes ?

Has anybody ever heard of Gravity Bleeding Brakes? Thats a new one on me. My GM mechanic friend said to crack the bleeder srews loose on both calipers and remove the cap from the Master Cylinder and about 15
minutes my line & new front hoses will be bled.
I've always opened the bleeder screw presses the brake pedal close the bleeder, let up on the pedal & repeat till I got a pint or so of brake fluid out.
========Harryface ======== 1991 Pontiac Bonneville LE 3800 V6 ( C ), Black/Slate Grey _~_~_~297,626 miles_~_~_
~_~_~_~_U.S.A._~_~_~_~_~_
~~~The Former Fleet ~~~ 89 Cavalier Z 24 convertible 78 Holiday 88 coupe 68 LeSabre convertible 73 Impala sedan
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Harry Face wrote:

They still will need to be bled properly but it gets the job 95% done anyway which can speed up the process.
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Harry Face wrote:

I do my car that way sometimes. Purges the old fluid ok. Turn a can upside down in the mstr cyl. Easy to forget and let the mstr cyl run out though.
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Harry Face wrote:

That sounds like a good way to introduce moisture into the hydraulic system. Use your way instead. Or the spray-bottle method...
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Harry Face wrote:

Yes, I do it all the time. If you only are replacing a hose and/or caliper, there is no need to go through some complicated bleeding procedure. On most vehicles, you will gravity bleed a front wheel circuit completely in a couple of minutes, if not less. The only thing extra that I do is.....after nothing but clear fluid comes out of the bleed screw, close it.....go in the vehicle and slowly pump the pedal a couple of times, then go back out and open the bleed screw again...usually you will get a couple more bubbles.

That works too. Though when you release the pedal while the bleed screw is open, you are sucking air back up into the system until you get to bleed screw and close it. This assumes you are doing it yourself. With a helper, this method works well. The gravity method is nice when you don't have a helper.
Ian
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On Fri, 21 Jan 2005 02:39:53 GMT, "shiden_kai"

Or get automatic bleed valves or a "one man bleeder" which is just a check valve in a line that fits over the bleeder valve.
Other method that works well is to put a small hose over the tip of the open bleeder and put the other end into a small container with a bit of fluid in it - enough to cover the hose end. Then stroke the pedal. Air bubbles come out, and when the pedal goes back up it draws in fluid instead of air. I've used this method many times over the last 35 or more years.
The advantage of the gravity bleed is you will NEVER trip a balance valve or brake failure indicator switch - and they can be MISERABLE to reset on some vehicles.
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shiden_kai wrote:

Hey! Whaddya know, that's the way I have been doing it at work too. Good to have a consensus view. GW
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Well I did the GB today - All went well with the passenger side, which I did first.
When I did the driverside I kept getting bubble after bubble coming down the hose into the jar. I thought this was beacause I removed the line from the master cylinder and it was taking longer to fill.
20 minutes later it dawned on me that there is an air pocket in the front part of the master cylinder due to the angle the car is jacked up on. I pulled the jack stands out & lowered the front end down and within a minute solid fluid was dripping out of the hose.
After gravity bleeding I did hit the brake pedal a few times to push out more fluid. What I do is ram the toolbox against the brake pedal and that holds it down till I can close the bleeder screw.
I may bleed the back brakes tomorrow when all the snow melts off the bottom of the car.
========Harryface ======== 1991 Pontiac Bonneville LE 3800 V6 ( C ), Black/Slate Grey _~_~_~297,626 miles_~_~_
~_~_~_~_U.S.A._~_~_~_~_~_
~~~The Former Fleet ~~~ 89 Cavalier Z 24 convertible 78 Holiday 88 coupe 68 LeSabre convertible 73 Impala sedan
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I've done this a couple of times in the past. I had a '79 Corvette about 9 years ago and that was the only way I could ever get all the air out of that car. The two man method just wouldn't get all the air out for some reason.
Brian
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The main reason you can gravity bleed the brake system now is that the car manufacturers put the bleeder screw on the top part of the wheel cylinder (that was not the case years ago when you had to bleed with someone assisting you or a pressure system to help you) Don't worry about moisture as you will not have the system open that long.Good luck

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All you have to do when the bleeder is not on top is unbolt the caliper and hang it from a wire oriented how you want. Then open the bleeder.
Brian
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wrote:

That was difficult to do with drum brakes.
Getting a solid pedal on some of the older british cars, like Vauxhaul Victor Specials and Viva HAs was a whole lot easier if you stood the car basically on end. Had one that I finally put on the twin-post hoist with the front about 4 feet higher than the rear and left it sit that way over night. The bubble worked its way up through the master cyl and the pedal was perfectly firm from then on. On another one, bleading it the normal way with the back end jacked up 4 feet finally did the trick (used an end-lift)
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