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B210 Booster Install Issues


jeffball610

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I’m currently running Z31 front and rear calipers and rotors with a 15/16” MC. Although this is adequate for street driving, the pedal is stiff and does not allow much modulation. This will make racing the car much more difficult. Recently I picked up a B210 brake booster, and although it physically fits in the car, the master cylinder bleeder screws touch my intake manifold. In fact, the casting of the MC touches the manifold. However, the booster should allow for more modulation of the pedal and make it safer to drive at a high level.
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So here’s my plan. It seems that I only need 8mm of bleeder screw engagement to seal the hole.
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The holes are approximately 12mm deep.
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I can “mill” off 4mm of the casting for clearance and still have a sealed MC. That being said, the bleeder screws are much longer than that. Since their only purpose is to bench bleed the MC, I can do that with full screws, and replace them with cut and welded screws.
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When welding the screw closed, I will need to make provisions for something to torque the screw into the hole. This should be simple enough by making a slit for a flathead screwdriver.
I didn't take a picture of this. I was too busy getting things working right.
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Right now, I seem to have clearance and the MC seems to hold fluid. I haven't pressurized it yet to see if the bleeder screws will leak.

What’s wrong with my plan? My other option is to use a ⅞” MC with the bleed screws on the other side. I will still have some clearance issues on that side, but not nearly as much. The downside is the reduced braking force from the smaller MC.

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The 7/8 won't reduce the braking force, just make it easier because the pedal travels farther.

 

If you had two identical systems but one a 1 7/8" and one a 15/16" you would find the 7/8 " easier to produce the same line pressure. However your pedal would travel farther. Same as a pulley system increases the mechanical advantage  and allows several pounds of pull to lift hundreds of pounds. 

 

I like your forward thinking of just plugging those holes. Once bench bled they are not needed. You could even trim some of the casting away for even more room.

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  • 2 weeks later...

I have had everything installed for about a week now. The pedal is almost nonexistent until the last few inches, and then it still doesn't stop very well. I presume there is air in the lines despite a complete fluid flush and bleed. I even went as far as to bleed the system using a tube from the caliper to the MC. The rear had a lot of air in it, but the fronts had none. When I press the pedal, I can feel it "wanting" to brake, but there just isn't much resistance or stopping power. It's not very safe to drive on the road, but I'm still doing it hoping I can bleed out whatever is trapped in there. If anyone has a better method, please let me know. I have a road course event on Saturday that is already paid for and I'm super excited for. However, if the car can't haul me down from 100mph, then it won't be safe on the track.

 

Any input is appreciated.

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2 minutes ago, thisismatt said:

Rear drums? Adjusted?

 

Wilwood 1" master has bleeders on the other side I think

I have full Z31 disks and calipers with a 280ZX 15/16" MC. A member on the Realm suggested a reverse bleed by pushing fluid from the caliper to the MC. I'll give that a shot.

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1 hour ago, jeffball610 said:

I have full Z31 disks and calipers with a 280ZX 15/16" MC. A member on the Realm suggested a reverse bleed by pushing fluid from the caliper to the MC. I'll give that a shot.

 

Easy way to do this if you don't have a mighty vac is to get a big syringe 30-60ml or so from a farm store and a little bit of rubber hose. The Luer Lock connector on most syringes happens to be close enough in size that the piece of hose slipped over it will also slip over the brake nipple. Makes it super easy to push fluid in from the caliper or to get air out depending on if you push or pull. Also brake fluid doesn't seem to eat the syringe (polypropylene likely). 

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12 hours ago, jeffball610 said:

I have full Z31 disks and calipers with a 280ZX 15/16" MC. A member on the Realm suggested a reverse bleed by pushing fluid from the caliper to the MC. I'll give that a shot.

If bleeding doesnt make any improvements try this.....

I have had something similar happen when I replaced a caliper on my Chevy.... it just wouldnt grab.... i think the piston in the caliper was a bit stuck, so no matter how much I bleed it the caliper wouldnt extend completely and grab.... So I removed the caliper, pumped the brakes a little to extend the pistons then pushed them back like I was putting new pads on... if its opposing pistons then once one side extends clamp a pad over that piston dont push it back, just keep it still, then a couple more pumps and get the other one to move.....

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I tried everything I could, and it still wasn't working. I took the car to a friend with a shop and we started from square one. We plugged a few minor leaks including redoing my MC bleed screw block offs. The bled the system again. Still felt like crap. So, we took the pushrod out from the booster and extended it some. It seems that the 15/16 MC has a deeper hole than the 7/8 MC. We extended the rod about 1/4 inch and it improved considerably. I'm still not happy with the engagement of the pedal, but it was good enough to get me on track and not fear for my life. I'll keep adjusting, but I'm still open to suggestions.

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  • 1 month later...

2 months later, and it's still not any better. My current explanation of the brake feel is "it slows the car, but it doesn't stop". I can feel the brakes engage at a decent spot in the pedal, but there is no more engagement with additional travel. At the bottom of the travel, the pedal stiffens up, but pushing harder doesn't do anything more.

 

I'm out of ideas and I'm open to any and all suggestions. My current mood it to go back to manual brakes. I'm fine with that, but I was hoping the booster would add some needed brake pedal feel and modulation. What are others running for brake set ups? Is everyone just running 15/16" or 7/8" manual brakes? Why do I see so many cars with B210 boosters if it doesn't work? I assume my booster works and holds vacuum because pressing the pedal with the motor off goes from "boosted feel" to manual feel after a press or two. I don't think my brake caliper set up is so far off from what others are running that it would have this profound of an effect. I'm at a loss here.

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