dv82xl Posted November 29, 2009 Share Posted November 29, 2009 Ok. first pardon me if THE answer is already here and I missed it - point me to it and I'll be eternally grateful and on my way. I have a 73 240z with a 400sb just for the fun of it. However - it's on blocks - no brakes! New Brake Booster. New Master Cylinder. Stock Rear Drums with new calipers. Stock Front Disc with new Toyota 4x4 calipers. I removed the pressure differential valve brcause I have a distinct feeling it will give me a problem I don't need. I have a proportioning valve. I bench bled the master. I have pressure fed more than a gallon of brake fluid to each corner starting with the farthest. I am convinced that there is no air in the system. The front brakes do not work - at all. The rears are not a problem they lock up. I've tried adjusting the proportioning valve all the way in each direction. No front brakes. Engine on. engine off - no front brakes. I've removed the front pads and checked that all 8 calipers move. Also, the brake pedal will not go to the floor stop, only 1/2 way and then - a hard stop at mid pedal travel. I've spent days and days on this. Actually considering scrapping the car. Shouldn't the pedal go all the way to the floor? Could it be that the booster and or master are defective? Do I need a master cylinder with a bigger volume? Quote Link to comment Share on other sites More sharing options...
mark Posted November 29, 2009 Share Posted November 29, 2009 Where exactly is the valve you removed and how did you remove it? Quote Link to comment Share on other sites More sharing options...
datsun79z Posted November 30, 2009 Share Posted November 30, 2009 dv82xl; Research "Reaction Disc" located in the brake section. I hope this helps you out. Mike Quote Link to comment Share on other sites More sharing options...
dv82xl Posted November 30, 2009 Author Share Posted November 30, 2009 The reaction disk thing - ya - I'll look for that - and I will really be miffed if that's the case - the MC and booster are both brand new. The valve I removed is, well all of them - there was a PDV & a distribution block - I removed all the brake lines - I actually took the car completely apart. I've done so many times in the past - and I've successfully put the car back on the road many times - but not this time! it's dark outside now so I can't see anything - I'll have a go at removing the master cylinder and booster - again - on Thursday - if it doesn't rain the real kicker is this - with all the talk on here about bigger disks here and brake upgrades there - I've replaced the entire drive train, built and installed my own wiring harness - I've rebuilt the entire car - even mounted my tires by hand - in my drive way - what the heck am I doing trying to sort out what seems to be a common brake system problem - with original equipment - on a car - that has no more original equipment in it? is there anyone out there that has - dare I say it - eliminated the booster and replaced the tiny MC? I mean - without anyone sending me an algebra lesson - I do not see the difference between the stock 7/8 and 15/16 bore of the 280zx MC - what I do see are MC's out there with 1.25 bores and huge fluid volumes - now that's a difference! I'm no sissy - I can handle the loss of power brakes - I don't have power steering right? I think I'm gonna go primitive and I'm just gonna buy the largest volume MC out there and bolt it in without the booster! Oh, ya I might have to fabricate something - oh my - as if that never happened! I mean - can you tell I'm frustrated? Really - I can't believe that people in here are spending multiple tens of thousands on their cars and keep the original brake system with it's goofy distribution blocks, PDV's and whimpy mc's? That just makes no sense to me. But then again....opinions vary Anyhow - I really appreciate the information here and any responses. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 30, 2009 Share Posted November 30, 2009 Is there anyone out there that has - dare I say it - eliminated the booster and replaced the tiny MC? I mean - without anyone sending me an algebra lesson - I do not see the difference between the stock 7/8 and 15/16 bore of the 280zx MC - what I do see are MC's out there with 1.25 bores and huge fluid volumes - now that's a difference! I'm no sissy - I can handle the loss of power brakes - I don't have power steering right? I think I'm gonna go primitive and I'm just gonna buy the largest volume MC out there and bolt it in without the booster! Oh, ya I might have to fabricate something - oh my - as if that never happened! John Coffey (http://www.betamotorsports.com) makes a conversion bracket to run dual master cylinders, one for the front and one for the rear brakes, without a booster. Some others (me included) have modded the stock pedal box to mount duals. One thing to take into account is that the stock pedal box was designed for the booster, so the brake pedal leverage ratio is something like 3:1 (going from memory here so cut me some slack if that's not exactly right). Most non-power brakes run 5 or 6:1 leverage ratios. That may not sound like a lot, but it is a big difference. Also, running a larger master will require MORE force on the pedal for the same force at the caliper. If you really wanted to run manual brakes, you'd want a smaller master cylinder for the same pedal effort, or ideally a different pedal leverage ratio and then similar to stock sized master cylinders. Quote Link to comment Share on other sites More sharing options...
johnc Posted November 30, 2009 Share Posted November 30, 2009 1. Get a copy of the factory service manual for your car. 2. Set the brake pedal height per the FSM. 3. Adjust the booster pushrod per the FSM. 4. Make sure you connected front and rear brakes to the correct ports on the MC. I do not see the difference between the stock 7/8 and 15/16 bore of the 280zx MC - what I do see are MC's out there with 1.25 bores and huge fluid volumes - now that's a difference! There's a big difference and just because you can't see it doesn't mean it doesn't exist. I can't believe that people in here are spending multiple tens of thousands on their cars and keep the original brake system with it's goofy distribution blocks, PDV's and whimpy mc's? That just makes no sense to me. Something isn't poorly engineered or bad just because you can't understand it. Quote Link to comment Share on other sites More sharing options...
dv82xl Posted December 3, 2009 Author Share Posted December 3, 2009 So, the answer is......already in here. As I suspected. I re read every post in here over the past couple of days. Then I dismantled the entire brake system today and went over everything piece by piece. And something showed up. Those Toyota calipers were upside down. I do not know how I ever got them to work in the past. I've had them upside down since I bought them years ago. I learned something else about the MC too. The first part of travel applies pressure to the front brakes. The back end applies pressure to the rears. The rears were never a problem - the proof of that was a very hard pedal mid way through the travel. Once I reversed the calipers and re bled the fronts - bingo. The pedal is very high now and the fronts grab nicely. I'm now conflicted with feeling happy and stupid at the same time. Quote Link to comment Share on other sites More sharing options...
Trevor Posted December 5, 2009 Share Posted December 5, 2009 I'm now conflicted with feeling happy and stupid at the same time. Be happy! You had a successful learning experience. Quote Link to comment Share on other sites More sharing options...
dan5138 Posted December 5, 2009 Share Posted December 5, 2009 O.O Ill have to keep this thread handy when I do my 4x4 conversion, so I don't make the same mistake. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted December 6, 2009 Share Posted December 6, 2009 Under the heading of "Teaching a man to fish ..." When you bleed the brakes the bubbles in the caliper are going to RISE, hence it's not going to work if the bleed nipple isn't at the highest point. Keep that in mind when you mount the calipers and it's unlikely you'll mount them backwards. Of course, you've now figured that out Hey, at least you had the courage to admit making a mistake. Read enough posts here and you'll see that we all (well most of us) make a few dumb mistakes. Quote Link to comment Share on other sites More sharing options...
dv82xl Posted December 6, 2009 Author Share Posted December 6, 2009 the worst form of pride is not being able to admit mistakes my personal favorite is setting my car on fire with my first harness - relay anybody? Oh that's what a fuse is for! my momma taught me "people that don't make mistakes - don't know s**t!" I appreciate all the input if I knew it all - I'd be very bored indeed & boring too! next agenda item - wheels & tires - I need more rubber on the road lots of pics in here but many are shy on details - maybe I need to look closer Quote Link to comment Share on other sites More sharing options...
Josh280z Posted September 20, 2010 Share Posted September 20, 2010 I dont know anything about totyota caliper upgrade system, but how did you get the calipers upside down??? dont the bleeder valves have to be sticking up? Quote Link to comment Share on other sites More sharing options...
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