gravity brake bleeding?????????

[bearlycontained]

I read a post somewhere here that I can't find now about doing a gravity bleed on the brakes that is supposed to work great. It was something about taking the master cylinder lid off and then open the furthest bleeder open till fluid comes out and then continue to the rest. It also said to make sure the master cylinder is always full. I don't remember if you put the lid on before you open a bleeder valve. Has anyone done this? How does it work? Should I just do the old have someone pump the pedal?

[ob1jeeper]

In a pinch, I've used a gravity bleed to "prime" the system, and IF you have a completely empty system, no help, and plenty of time, a gravity bleed can be done to get the system MOSTLY full (primed)...

HOWEVER, there are two issues with leaving the system open for a gravity bleed...
1- unless you're using a synthetic fluid, the vast majority of brake fluids not only can, but WILL readily absorb moisture from the air, thus you will end up with a high likelyhood of moisture contamination in your system... (BAD... causes corrosion, and loss of brake pressure due to gassing when the moisture boils during heavy load braking...:()

AND the most important reason...

2-A gravity bleed cannot remove ALL trapped air, thus should ALWAYS be followed up by a proper final bleed to ensure ALL trapped pockets of air (and moisture) are removed, prior to operating on public roadways, or in places where you will need to bet your life on the fact that they will work properly...

HTH... Good Luck...

[lostoffroad]

just did this on my rig. just took of the cap, made sure it was full and opened the bleeder. i waited till i had a little fluid come out and then went to the next. didnt even final bleed them. i do use synthetic fluid. ill probly final bleed them later. but in all my experiences with gravity bleeding it had done a great job. just leave the cap off while your doing it or itll stop the fluid from leaving the master cylinder. hope this helps.

[TRobertsRN]

Your local auto parts store sells a kit for self bleeding brakes to where one person can do the job via not just gravity but by pumping the brakes to insure no air.

The way it works is a clear hose that goes to a clear bottle. May even have a check valve in the hose (it has been a while).

You keep the cylinder full as possible as you said, hook the kit to the farthest away from the master cylinder brake line and pump the brakes a few times then go check the clear hose a bottle for bubbles. Repeat with the next farthest away and so on.

If you have replaced the master cylinder a "bench bleed" is usually needed.

Tom

[rosshh]

or just get speed bleeders from the "help" section at any auto parts store... they replace the bleed bolt and make it very easy.