brake bleeding dry system
Thread Starter
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Joined: May 2007
Posts: 62
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From: scarborough maine
brake bleeding dry system
new lines, new master cylinder, new booster. bleed the front two and that was easy, then opened up the back bleeder and couldn't pump fliud down there.... nothing. the back half of the master cylinder fliud level didnt drop. the system is dry btw. any advice?
Le Mans Master
Joined: Oct 2006
Posts: 7,123
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Did you bench bleed the master before you installed it? If not, you'll need to pull it off and do so. After you installed it, the front system filled up first (shorter distance for the fluid) and now the rear won't fill because there's not enough stroke in the pedal.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
Always bench bleed a new or rebuilt master cylinder.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
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From: Kingston Ontario
Sounds like the combination valve is not centered. Do you have a brake warning light illuminated on the dash? If the light is on, this would indicate that the valve has been pushed over internally because you only had front brake pressure.
Are you using a pressure bleeder, two man, static?
You have to continue to bleed the rears in order to re-center the combination valve. I have cracked open the front brake bleeder valve before in an attempt to allow the combination valve to shift internally, while applying brake pressure. Keep bleeding, you'll get there.
Are you using a pressure bleeder, two man, static?
You have to continue to bleed the rears in order to re-center the combination valve. I have cracked open the front brake bleeder valve before in an attempt to allow the combination valve to shift internally, while applying brake pressure. Keep bleeding, you'll get there.
Thread Starter
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Joined: May 2007
Posts: 62
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From: scarborough maine
yes the brake light it on in the corvette, and i think you right with the valve being off centered. question is, now that the front brakes are good and the back ones are still dry and im getting nowhere with bleeding them, what should i do?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I think a set of check valve speed bleeders would help you here. They cost about $8 for a set of two at most auto parts stores. You simply install them in place of your stock bleeders. These are special because they have a spring loaded ball valve that will not let air back in, and fluid will only be forced out when pressure is applied to the pedal.
You install the bleeders, and on one of the front calipers, crack the new bleeder and slip a long clear plastic tube onto the end of the valve. Run that plastic tube into a catch bottle for the fluid so you can add it back to the master as the fluid levels drop. Then, do the same to one or both of the rear calipers, and go depress the pedal a few times.
Once you get fluid moving to the rear system, close the front bleeder, and one of the rear calipers, and start bleeding again one caliper at a time starting further away. Always, furthest away, starting with the rear system.
Also, tap on the calipers and master with a wooden handle to help knock loose any air bubbles that are sticking to the insides.
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Thread Starter
Advanced
Joined: May 2007
Posts: 62
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From: scarborough maine
by the way i forgot to mention....before i replace the lines and master cylinder the back resovoir once ran out completley empty and air go into the back, so that could have made the valve close completly shut....
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
You may have to remove the master cylinder and bench bleed again.
You can also try this before you bench bleed. Crack open the brake line at the outlet of the first component downstream of the master cylinder. That is the combination valve. If you get fluid going through the valve then just tighten the fitting and continue to bleed the rears. If you don't get fluid flow, bench bleed the master again.
You can also try this before you bench bleed. Crack open the brake line at the outlet of the first component downstream of the master cylinder. That is the combination valve. If you get fluid going through the valve then just tighten the fitting and continue to bleed the rears. If you don't get fluid flow, bench bleed the master again.
