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Gravity Bleeding Brakes

Joined
Mar 9, 2009
Messages
1,026
Location
Yemen
I have always gravity bled my brakes and have never had a problem. Many folks have a LOT of problems because they don't do it right:

1. The master cylinder lid must be off and kept at least 90% full during the bleeding process

2. The bleeder screw can't be plugged with debris so take it all the way out and clean it if necessary before trying to bleed

3. Bleed until the fluid coming out is a steady drip drip drip drip drip drip drip drip drip drip drip drip about 1/2 second apart

4. In the cold winter months it can take 30 minutes or more for fluid to begin dripping out the rear bleeders if the lines are empty so be patient

5. If you don't have the patience to wait 30 minutes use a Mighty Vac to suck on the bleeder screw and you can have fluid flowing within 15-20 seconds

If you have a Mighty vac its not necessary to bench bleed a new master cylinder because the suction of the Mighty Vac will do the job very quickly. Just remember to use the Mighty Vac on the front bleeders AND the rear bleeders because the master cylinder has two reservoirs. For the early C3's with the adjustable master cylinder push rod make sure the rod is adjusted short enough to allow about 1/2" of pedal "free play" before the master cylinder piston gets pushed. That ensures the pistons can fully retract so the upper reservoir can feed the piston bores.
 

bill81vette

Moderator
Joined
Jan 17, 2004
Messages
4,316
Location
Troy,NY
Corvette
1981 dark blue metallic
Now I know how NOT to do this

Sent from my XT1650 using Tapatalk
 

LLC5

Well-known member
Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
I have always gravity bled my brakes and have never had a problem. Many folks have a LOT of problems because they don't do it right:

1. The master cylinder lid must be off and kept at least 90% full during the bleeding process

2. The bleeder screw can't be plugged with debris so take it all the way out and clean it if necessary before trying to bleed

3. Bleed until the fluid coming out is a steady drip drip drip drip drip drip drip drip drip drip drip drip about 1/2 second apart




Exactly how many drips does it take?
 
Joined
Mar 9, 2009
Messages
1,026
Location
Yemen
Biggest Problem With Gravity Bleeding Brakes

I think the biggest problem is people THINK their brakes have been bled the moment they see a few drops coming out of their bleeder screws. However a few drops could mean there is still 6 feet of air in the line that needs to be bled so their brakes are still real spongy. They must have more patience and wait until the dripping is continuous and it could take 30 minutes or more to achieve that in cold conditions. By sucking on an open bleeder screw with a Mighty Vac they can move a LOT of air thru the line in just a few pumps.
 
Joined
Mar 9, 2009
Messages
1,026
Location
Yemen
Rebuilt Right Front Brake Caliper

I recently rebuilt my right front brake caliper and during the overhaul my master cylinder reservoir completely drained. After I reinstalled the caliper I filled the master cylinder and it took about 30 minutes for the fluid to begin running out of the bleeder screw. The point I'm making is it takes a LONG time for brake fluid to run thru 6 feet of 3/16" tubing, fill the caliper, then run out of the teensy tiny bleeder screw hole. When gravity bleeding brakes people need to be patient.
 

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