"Gravity" brake bleeding?

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animal

Well-known member
Joined
Nov 24, 2011
Messages
1,160
Location
Downtown Hooper, CO
All the parts on my Ford's brake system are new, from the M/C to the calipers and all lines and hoses. I was talking to a guy today about bleeding the system, and he mentioned (and swears by) gravity bleeding...as I understand it, you fill the master cylinder and let the fluid run to all four wheels until fluid starts leaking from the M/C fittings, which are just barely loosened. Then tighten fittings and finish bleeding each wheel using the bleeders. Is this for real? I've never heard of this method.
 
I've changed calipers this way, fill the master, remove the hose and install on new one with the bleeder open. when the fluid begins to drip tap on caliper to release air bubbles and tighten and your done.With a whole system dry this method may give you trouble with air bubbles trapped at fittings and calipers but its a good way to start then do a pump,hold release method.
 
I did the complete new system bleed on my car that way. I opened the bleed valve farthest from the master, when it started dripping, closed it, opened the next closest, etc until all four had fluid. Did a normal pump bleed then, all was good to go. I didn't have any problems with air, but my car is 4 wheel drums.
 
I have done that on both my sedans. No problems on the first but the new one is giving me fits. I believe it's the master cylinder though.
 
Gravity bleed is all I've used for decades, on hundreds of cars. If the parts are new and empty, I very lightly pump the pedal by hand to get the calipers/wheel cylinders filled up. I can't say I remember it ever not working. Always remember to bench bleed a new master cylinder.
 
I've done it. it works. I bleed most of my brake work with vaccuum. I use a tank that I evacuate with an vaccuum pump for air conditioning work and then hook it up to the bleeders to draw fluid trough the system. It works the same as gravity method just faster. It' great for working alone.
 
I saw somewhere a long time ago, a guy loosened all the bleeders, put a piece of vacuum line on the bleeder screws and the other end of line in pop bottles full of brake fluid. When he pushed the pedal, the bubbles came out and sucked the fluid back in when when he released the pedal. He did all 4 at once. I always wanted to try this. I don't see why i wouldn't work but now that my kids are older, they help me.
 
Does anybody use air pressure to bleed brakes anymore? I worked for a guy years ago that had made adapters to clamp on top of the master cylinder with an air chuck in it. You just clamped it on top of the open master cylinder and hooked up the air hose. Then you bled each wheel cylinder. A one person job.
 
I've done it with the pressure method. It works. I like the vaccuum way better. It is easier to add fluid as you go and less likely to spray fluid where you don't want it.
 

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