logan1 Posted October 10, 2011 Share Posted October 10, 2011 (edited) Ok so I've been trying to bleed my brakes all day today and still cant get it to work. My car is a 1970 240z and has the Toyota S12W brakes in the front and the 280ZX disk brake conversion on the back; I'm running SS braided brake lines between the hard lines and the calipers and also have the larger 280ZX master cylinder installed. From what i can tell there are no bubbles in the lines as i can have someone sit in the car and pump the breaks and when i open the bleed screw i shoots out a steady stream of brake fluid. I read a bunch of stuff on the site and as instructed started by bleeding the MC and them proceeded to bleed the 4 calipers. I have not bleed through almost 2 quarts of DOT-3 brake fluid and the pedal still goes all the way to the floor with little to no resistance. However if i pump the brake 5 or 6 times it gets firm and provides enough pressure to the calipers to stop the wheels from moving. Also when i pump the brake the fluid lvl in the master cylinder starts to drop and holds steady after about 4 pumps of the pedal and when the pedal is released the fluid lvl slowly start to rise back up. I'm not sure what i need to try next? Edited October 10, 2011 by logan1 Quote Link to comment Share on other sites More sharing options...
Leon Posted October 10, 2011 Share Posted October 10, 2011 Are all of your bleeders at the top of your calipers? Quote Link to comment Share on other sites More sharing options...
Miles Posted October 10, 2011 Share Posted October 10, 2011 I am having the same problem. Hope you will post your solution. Quote Link to comment Share on other sites More sharing options...
Miles Posted October 10, 2011 Share Posted October 10, 2011 (edited) Ok so I've been trying to bleed my brakes all day today and still cant get it to work. My car is a 1970 240z and has the Toyota S12W brakes in the front and the 280ZX disk brake conversion on the back; I'm running SS braided brake lines between the hard lines and the calipers and also have the larger 280ZX master cylinder installed. From what i can tell there are no bubbles in the lines as i can have someone sit in the car and pump the breaks and when i open the bleed screw i shoots out a steady stream of brake fluid. I read a bunch of stuff on the site and as instructed started by bleeding the MC and them proceeded to bleed the 4 calipers. I have not bleed through almost 2 quarts of DOT-3 brake fluid and the pedal still goes all the way to the floor with little to no resistance. However if i pump the brake 5 or 6 times it gets firm and provides enough pressure to the calipers to stop the wheels from moving. Also when i pump the brake the fluid lvl in the master cylinder starts to drop and holds steady after about 4 pumps of the pedal and when the pedal is released the fluid lvl slowly start to rise back up. I'm not sure what i need to try next? Did you adjust the pushrod between the booster and the 280ZX MC? It has to be adjusted longer. see :http://forums.hybridz.org/index.php?showtopic=46973 Another question that comes up often is "is the reaction disk in the booster missing". There is a write up in the brake section on this. Edited October 10, 2011 by Miles Quote Link to comment Share on other sites More sharing options...
neotech84 Posted October 10, 2011 Share Posted October 10, 2011 Yup, reaction disc OR bad booster (leaky) usual cause of said lack of pressure. Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 11, 2011 Share Posted October 11, 2011 (edited) If they pump up and the fluid drops in the reservoir, you have a big air bubble in the system. Probably in the calipers, because the bleed screw is not positioned at the top of the cylinder like it should be. The fluid is taking the place of the air as it is compressed by pumping the pedal. The air doesn't come out because the fluid just passes under the bubble on its way out the bleed screw. If you look at the caliper you'll probably be able to discern the shape of the cylinder that the piston rides in. The bleed screw, if its port is drilled straight in to the cylinder, should be at the top of the cylinder, while bleeding. It's position will depend on how the engineers designed the caliper mounting on the car they came from. I've heard that some times you'll have to remove the mounting bolts and reposition the caliper to get the bleeder on the top. As long as the pistons are squeezing the rotor, or even a block of wood, you can bleed them that way then reposition them and bolt them back down for use. Edited October 11, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted October 11, 2011 Share Posted October 11, 2011 I had same problem. Try running a tube from the master cyl bleeder screw and the reservoir to get all that air out. I had to take off my rear calipers and bleed them while rotating them at multiple different angles to get all the air out. Does anybody know if stock 240z FRONT calipers have to be rotated around like that to get all the air out-or is the stock location ok for bleeding? Quote Link to comment Share on other sites More sharing options...
logan1 Posted October 11, 2011 Author Share Posted October 11, 2011 (edited) Are all of your bleeders at the top of your calipers? No all my bleed valves are at the bottom of the calipers Did you adjust the pushrod between the booster and the 280ZX MC? It has to be adjusted longer. see :http://forums.hybridz.org/index.php?showtopic=46973 Another question that comes up often is "is the reaction disk in the booster missing". There is a write up in the brake section on this. Kool thanx for the info. I had not adjusted my pushrod to account for the new 15/16 MC. I adjusted the pushrod as instructed in the thread you linked and the pedal felt a little better. I had same problem. Try running a tube from the master cyl bleeder screw and the reservoir to get all that air out. I had to take off my rear calipers and bleed them while rotating them at multiple different angles to get all the air out. Does anybody know if stock 240z FRONT calipers have to be rotated around like that to get all the air out-or is the stock location ok for bleeding? I'll be doing the same thing for the front and rear tomorrow. If they pump up and the fluid drops in the reservoir, you have a big air bubble in the system. Probably in the calipers, because the bleed screw is not positioned at the top of the cylinder like it should be. The fluid is taking the place of the air as it is compressed by pumping the pedal. The air doesn't come out because the fluid just passes under the bubble on its way out the bleed screw. If you look at the caliper you'll probably be able to discern the shape of the cylinder that the piston rides in. The bleed screw, if its port is drilled straight in to the cylinder, should be at the top of the cylinder, while bleeding. It's position will depend on how the engineers designed the caliper mounting on the car they came from. I've heard that some times you'll have to remove the mounting bolts and reposition the caliper to get the bleeder on the top. As long as the pistons are squeezing the rotor, or even a block of wood, you can bleed them that way then reposition them and bolt them back down for use. All of my bleed valves are at the bottom of the calipers. Tomorrow i'll take the calipers of the mounts and see if i can bleed then with the bleed screw at the top. I'll report back as to how it turns out. Edited October 11, 2011 by logan1 Quote Link to comment Share on other sites More sharing options...
ritrebor Posted October 11, 2011 Share Posted October 11, 2011 If your bleed valves are on the bottom, you might be able to swap sides so they will be on top. ritrebor Quote Link to comment Share on other sites More sharing options...
Miles Posted October 11, 2011 Share Posted October 11, 2011 Tips on push rod adjustment: Don't adjust the push rod adjustment out too far or you will lock your brakes up. The MC piston has to return far enough to allow fluid in the MC to drain out through a return port inside the MC. Long story, but there are threads on this issue in the brake section. If you should lock your brakes up by over extending the push rod simply open the bleed screws on the MC with a 10mm wrench to relieve the pressure and limp home. And then back off the rod adjustment in small increments until no more lock up. Another tip on adjusting the push rod. You don't have to remove the MC to adjust the push rod. There is enough flex in the hard pipes that connect to the MC that you can just remove the nuts from the MC mount, pull it forward and gently push it aside to allow access to the push rod adjustment. When I swaped in a 280ZX MC into my 72 240Z I used this technique to fine tune the length of the push rod. There is also an adjustment on the break pedal under the dash you can adjust to get less or more pedel throw. Be aware that pulling the push rod out to adjust it can result in dropping the reaction disk inside the booster. This will cause a long pedal throw followed by the brakes suddenly grabbing and nose diving the car. There is a good write up on this in the brake section or in the FAQ section on brakes. Quote Link to comment Share on other sites More sharing options...
Leon Posted October 11, 2011 Share Posted October 11, 2011 No all my bleed valves are at the bottom of the calipers Well there's your problem. Swap left-to-right and you'll be good to go. Quote Link to comment Share on other sites More sharing options...
stony Posted October 11, 2011 Share Posted October 11, 2011 Well there's your problem. Swap left-to-right and you'll be good to go. Agree with above..... The other possible solution for this is to bench bleed the master cylinder. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted October 11, 2011 Share Posted October 11, 2011 When I installed a ZX master in my Z had the same problem. There are bleed ports on side the master cylinder, I bled them and the problem went away. I just used the old hose into a beer bottle with brake fluid methold. Quote Link to comment Share on other sites More sharing options...
logan1 Posted October 11, 2011 Author Share Posted October 11, 2011 (edited) Ok so i took the day off work to day and swapped the left and right calipers as instructed. Then I started bleeding the system again starting with the MC and then the 4 calipers and now the brake pedal is tight as a drum. It moves down approx 1" down before it starts to engage and bottoms out after approx 3-4" of travel. the braked seem to be working well as i am unable to move the wheels by hand once the brake is engaged. I cant drive my car yet but i think the brake problem is fixed. Also i don't think i extended the push rod in the brake booster too much but i'll know for sure next week once the car is on the road. I really appreciate you guy taking the time to trouble shoot my car problems. thanx John Edited October 11, 2011 by logan1 Quote Link to comment Share on other sites More sharing options...
Miles Posted October 11, 2011 Share Posted October 11, 2011 Let us know how the road test goes. Quote Link to comment Share on other sites More sharing options...
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