Gravity bleeding the brakes
Thread Starter
Advanced
Joined: Jun 2006
Posts: 52
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From: N.W. Illinois
Gravity bleeding the brakes
Just how long should this take?
I have a new 1964 style (Napa) m.c. Which I have bench bled very slowly with DOT 5 silicone fluid untill I can't get any more bubbles out and about 1/8" travel. Installed on my car with 4 new calipers(65-67 style) 2 new ss rear hard lines, 4 new rubber hoses. Completely dryed and cleaned out system. I opened all 6 bleeders and nothing after 3 hours. So I took line off of m.c. and blew air threw system, and air passed at all bleeders. Put back together and waited another 2 hours. Nothing. So I got anxious and closed all bleeders but one and very slowly manually bled untill all calipers were full, then tried to gravity bleed again. 2 hours- nothing. What the hell ?
I have a new 1964 style (Napa) m.c. Which I have bench bled very slowly with DOT 5 silicone fluid untill I can't get any more bubbles out and about 1/8" travel. Installed on my car with 4 new calipers(65-67 style) 2 new ss rear hard lines, 4 new rubber hoses. Completely dryed and cleaned out system. I opened all 6 bleeders and nothing after 3 hours. So I took line off of m.c. and blew air threw system, and air passed at all bleeders. Put back together and waited another 2 hours. Nothing. So I got anxious and closed all bleeders but one and very slowly manually bled untill all calipers were full, then tried to gravity bleed again. 2 hours- nothing. What the hell ?
Burning Brakes
Joined: Jun 2008
Posts: 1,194
Likes: 13
From: Seattle area, WA (On the Eastside)
I've done only two gravity bleeds and the last one I may not have waited long enough and I may still have air in the lines.
I'm not so sure about this but I was told to open just one bleeder at a time, not all at once. I started getting fluid out of each one in about 10 minutes and you have to monitor it so the MC won't run dry.
I think it took me about an hour for the whole job.
Since it pulls to the right when braking, I think there's still air in there, so I'm taking it to a brake shop to get it bled right and checked out. I'm going open track racing in three weeks and need good brakes.
I'm not so sure about this but I was told to open just one bleeder at a time, not all at once. I started getting fluid out of each one in about 10 minutes and you have to monitor it so the MC won't run dry.
I think it took me about an hour for the whole job.
Since it pulls to the right when braking, I think there's still air in there, so I'm taking it to a brake shop to get it bled right and checked out. I'm going open track racing in three weeks and need good brakes.
Racer
Joined: Jul 2004
Posts: 420
Likes: 0
From: Langley British Columbia
I've got a 1973. 1 hour. 2 hours. Nothing. I ended up trying to gravity bleed my new MC overnight, still nothing. (Of course I did the bench work a few times prior to trying the gravity bleeds. Not a fun time if you've ever installed a master in one of those cars!)
Finally ended up brazing an air fitting onto an old cover and made my own pressure bleeder. Works like a charm.
Al
Finally ended up brazing an air fitting onto an old cover and made my own pressure bleeder. Works like a charm.
Al
Melting Slicks
Joined: Sep 2003
Posts: 3,050
Likes: 2
From: Orange Ct
The last time I changed my MC I had trouble getting a pedal. Out of frustration, I just started pumping the pedal. After about 50 strokes the pedal got hard and all was good. (Don't even go there with the use of certain word combination's in this post)
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
I gravity bled my lines after replacing all the brake lines. The calipers still had old fluid. The master cylinder was dry. I just filled the reservoir with dot 5 and opened the farthest bleeder. I had a hose connected to the bleeder going into a glass jar and waited for the dot 5 to come out. Took about 1 beer per wheel. (For the wheel closest to the master I really had to drink fast!) I never bench bled, and I have a good pedal. You have to make sure that the plunger in the master is not pushed in at all, because that will stop the flow.
Gerry
Gerry
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Have you ever syphoned gas out of a car? If you have you would understand, that thing ain't going to do anything until you get the air out of the lines. You have to do the pump method first first to get it flowing, and then gravity drain.
Racer
Joined: Jan 2005
Posts: 411
Likes: 3
From: New Jersey
Brake bleeding
I my opinion the best way to bleed the brakes is by PRESSURE BLEEDING period.
I bench bled the master cyl.
I went to ACE hardware , bought the smallest [weed killer ] type sprayer,
Made a flat piece of aluminum with a tapped hole in it. to fit on top of the master cyl.
Put a 0 to 15 pressure guage on it .
Conected all together with brass fittings. I used a fitting under the metal about a half and inch long so that when I took off the metal plate the fluid would not over flow the master cyl. and drip all over the fire wall of the car.
Made a gasket out of neoprene.
used a "C" clamp to hold the flat piece of metal to the M. Cyl.
Put brake fluid in the container [sprayer] Pumped up the container with the pump on it.
Put between 5 to 10 lbs. of press. on system.
Opened up the fitting fartherest away. [ had tubing on it. and used a glass jar] Until I saw the fluid with no bubbles [ did the other three]
Was done in no time flat, went into the house told my wife I must have done something wrong because that bleeding was way too easy.
Never touched the system since .
There is a company that makes this very same sys. for about 80 bucks if you do not want to make one.
I bench bled the master cyl.
I went to ACE hardware , bought the smallest [weed killer ] type sprayer,
Made a flat piece of aluminum with a tapped hole in it. to fit on top of the master cyl.
Put a 0 to 15 pressure guage on it .
Conected all together with brass fittings. I used a fitting under the metal about a half and inch long so that when I took off the metal plate the fluid would not over flow the master cyl. and drip all over the fire wall of the car.
Made a gasket out of neoprene.
used a "C" clamp to hold the flat piece of metal to the M. Cyl.
Put brake fluid in the container [sprayer] Pumped up the container with the pump on it.
Put between 5 to 10 lbs. of press. on system.
Opened up the fitting fartherest away. [ had tubing on it. and used a glass jar] Until I saw the fluid with no bubbles [ did the other three]
Was done in no time flat, went into the house told my wife I must have done something wrong because that bleeding was way too easy.
Never touched the system since .
There is a company that makes this very same sys. for about 80 bucks if you do not want to make one.
Last edited by lovevettes; Jul 7, 2010 at 10:09 AM.
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Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
Gerry
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
I have found this to be very true. Not just on Corvettes, either.
I have also found that if you are working on a car with a brake distribution block, if you'll crack the line(s) at the block first, the fluid will drain to that point and then you can continue the gravity bleed.
I also know that what I just reported is not 100% consistent and I don't know why.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
I would guess you system is designed about like any other 66. You may get it flowing at some time, but I ain't got that much beer.
Thread Starter
Advanced
Joined: Jun 2006
Posts: 52
Likes: 0
From: N.W. Illinois
I gravity bled my lines after replacing all the brake lines. The calipers still had old fluid. The master cylinder was dry. I just filled the reservoir with dot 5 and opened the farthest bleeder. I had a hose connected to the bleeder going into a glass jar and waited for the dot 5 to come out. Took about 1 beer per wheel. (For the wheel closest to the master I really had to drink fast!) I never bench bled, and I have a good pedal. You have to make sure that the plunger in the master is not pushed in at all, because that will stop the flow.
Gerry
Gerry
Last edited by Early 63; Jul 8, 2010 at 12:07 AM. Reason: mispell
Racer
Joined: Jul 2004
Posts: 420
Likes: 0
From: Langley British Columbia
I had the LH rear bleeder open first I think (I followed the directions found on a the forum thread). I had to keep taking the cap off to refill.
If I had to do it over, I'd buy one of the pressure bleeders shown in JohnZ's post. They are only $60.00 or so, but would be easier to use.
Last edited by Uncle Ralphy; Jul 8, 2010 at 01:22 AM. Reason: Clarification
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Burning Brakes
Joined: Mar 2008
Posts: 859
Likes: 53
From: Magnolia Texas
The new master cylinder makes me wonder.... some disc brake master cylinders have a small rubber check valve in them to prevent all the pressure from returning which is designed to hold the pads against the rotor. I wonder if your master cylinder has that? With no lines connected to it, there should be fluid dripping from the outlets. If not, I would check for that small valve. I can't remember where or how it was implemented but if you get no fluid dripping, I don't think you will get there by gravity bleeding.
BTW, when I gravity bled mine, I had fluid at the caliper(s) in just a few minutes.
Hope that helps,
Steve
BTW, when I gravity bled mine, I had fluid at the caliper(s) in just a few minutes.
Hope that helps,
Steve
Drifting
Joined: Oct 2008
Posts: 1,936
Likes: 92
From: Rochester Hills Michigan
I know the guys in the GM shop used gravity bleed back in the day. I'm assuming (haven't played with brakes for years...make that decades) that all the fluid for a gravity bleed flows through the compensating port, which is tiny. Guess that's why it takes so long? Anyway, check to make sure your compensating port is open.
Race Director
Joined: Feb 2007
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From: northern california
C2 of Year Finalist (track prepared) 2019
Jim