I'm too lazy to get someone else to help.
Bleeding a Hydrovac Brake System
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Senior User
Joined: Jul 2007
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From: SE / NWL MI
Bleeding a Hydrovac Brake System
This information was provided in another thread that was covering several topics. It was suggested that it be split out into a new thread as it may be beneficial to others as well.
Bleeding A Hydrovac Brake System, Manual
Manual bleeding requires filling the master cylinder reservoir and pumping the brake pedal to force the fluid through the lines to expel air from the system. This operation must be done with the engine shut off and no vacuum in the power brake system.
With the master cylinder reservoir filled, open No.1 bleed screw on the Hydrovac and depress the brake pedal to expel air. When the brake pedal has reached the toe board, close the bleed screw before returning pedal to release position. Repeat this procedure until soild fluid, free from bubbles, comes from the bleed screw. Check the master cylinder frequently to insure an ample supply of fluid.
<O
Using this method, bleed No.1 and No.2 bleed screws on the Hydrovac and then proceed to the vehicle wheel cylinders. Then start with the wheel cylinder farthest from the master cyl and work your way to the wheel that's closest; typically Rr, Lr, Rf, Lf.
Bleeding A Hydrovac Brake System, Manual
Manual bleeding requires filling the master cylinder reservoir and pumping the brake pedal to force the fluid through the lines to expel air from the system. This operation must be done with the engine shut off and no vacuum in the power brake system.
With the master cylinder reservoir filled, open No.1 bleed screw on the Hydrovac and depress the brake pedal to expel air. When the brake pedal has reached the toe board, close the bleed screw before returning pedal to release position. Repeat this procedure until soild fluid, free from bubbles, comes from the bleed screw. Check the master cylinder frequently to insure an ample supply of fluid.
<O
Using this method, bleed No.1 and No.2 bleed screws on the Hydrovac and then proceed to the vehicle wheel cylinders. Then start with the wheel cylinder farthest from the master cyl and work your way to the wheel that's closest; typically Rr, Lr, Rf, Lf.
Elder User
Joined: Jun 2008
Posts: 693
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From: N E Ohio
I have never been able to properly bleed a systen with a remote booster with a vacuum bleeder.
If you have no pedal at all, I suggest doing a part by part test -
1 - remove brake line at master cyl and plug master cyl. If pedal is good, master cyl is good.
2 - Reconnect master cyl, ans disconnect the lines to all wheel cylinders from remote booster, plug remote booster. Bleed remote booster and then check pedal, if it is good remote booster is good.
3 - Reconnect front brakes, plug/cap lines to rear brakes. Bleed front brakes. Check pedal, if it is good, front brakes are OK.
4 - Reconnect rear brakes, and bleed them. For dual cylinder brakes I have found that you need a helper who can really apply the brakes hard. Make sure you open the bleeders as much as possible to get a strong stream. If the wheel cylinders are good, this should result in a good pedal. You may then want to rebleed the fronts to make sure all air is removed.
If you start with a "pedal to the floor" and a simple bleed has no effect, I have found that the above procedure and a helper is the only way to go. Good luck.
If you have no pedal at all, I suggest doing a part by part test -
1 - remove brake line at master cyl and plug master cyl. If pedal is good, master cyl is good.
2 - Reconnect master cyl, ans disconnect the lines to all wheel cylinders from remote booster, plug remote booster. Bleed remote booster and then check pedal, if it is good remote booster is good.
3 - Reconnect front brakes, plug/cap lines to rear brakes. Bleed front brakes. Check pedal, if it is good, front brakes are OK.
4 - Reconnect rear brakes, and bleed them. For dual cylinder brakes I have found that you need a helper who can really apply the brakes hard. Make sure you open the bleeders as much as possible to get a strong stream. If the wheel cylinders are good, this should result in a good pedal. You may then want to rebleed the fronts to make sure all air is removed.
If you start with a "pedal to the floor" and a simple bleed has no effect, I have found that the above procedure and a helper is the only way to go. Good luck.
Mountain Pass
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Cargo Master
Joined: Jul 2009
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From: Des Moines
Just be cautious in how far you back them off (if star wheels - cam adjusters can be backed off all the way) - I backed one off too much and it started leaking when I started bleeding them. I would guess only backing them off enough to remove the drum is good, but I haven’t had the chance to experiment.
Cargo Master
Joined: Jul 2009
Posts: 2,538
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From: Des Moines
If you don’t have a pressure bleeder, I’d recommend gravity bleeding to start, just to get some fluid in the lines, then manual bleeding with a helper to make sure it’s all purged.
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