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After rebuilding front and rear calipers and bleeding the brakes there was now too much brake pedal travel before the pedal became firm. The pedal just goes down too far before I felt anything. Once I felt resistance the pedal was solid, not spongy. Others on this forum reported a similar problem but I did not find a fix. Brake pedal travel before the calipers were rebuilt was fine, so I was certain I was overlooking something.
To set the stage, I sucked the fluid out of the master cylinder reservoir and then disconnected brake lines at the calipers. As expected, quite a bit of fluid drained out of the brake lines.
After the calipers were rebuilt I bled the brakes, done this dozens of times on family cars so no need to check the shop manual :oops:. But now the pedal goes down too far before feeling anything. Bled the brakes again and again with no change in the problem.
A close reading of the shop manual and a tip from Eric O. of South Main Garage solved this problem.
First, the shop manual has a warning saying you have to bleed the front and rear calipers on one side simultaneously. Okay, why is that and how is it going to solve my problem.
The answer is when brake fluid drained out of the brake lines it let air into the master cylinder. The master cylinder has two chambers, one for the front calipers and the other for the rear calipers. You bleed the master cylinder by opening bleed valves on the front and rear of one side at the same time, passenger side for example, and pushing the brake pedal. This lets the master cylinder piston push fluid (and air) out of both chambers.
I used a pressure bleeder, and while bleeding the front and rear calipers on the passenger side simultaneously I pressed the brake pedal 3 or 4 times (thank you Eric O) and then closed the bleeder valves. Did the same for the drivers side and now my brake pedal works like new.
This is the pressure bleeder I used, not too expensive.
1611166
 

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I have that seem pressure bleeder. What is the master cylinder cap Part number for 85 spider That you’re using?
Thank you, Steve
 

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But Mad North-Northwest
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See, you made your life harder by draining the MC and lines. Easy way is to stick a rubber vacuum cap over each hard line after you disconnect it from the caliper. This keeps the lines and MC full and then you only need to get the air out of each caliper.

If you look closely, the outlets to the left front and the rear are at the top of their respective cylinder sections. What I do with a dry MC is leave all three fittings loose at the MC, then fill the reservoir and let it sit for a few minutes. Fluid will come out the RF first, when that happens snug it up. Then do the same when fluid comes out the LF and the rear fittings. Voila, your MC is bled...don't even need to hit the pedal and make a mess.

I've got the same pressure bleeder and it works a treat.
 

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But Mad North-Northwest
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Actually, in looking at the options I'd suggest spending a little more and getting the 1109. Bit more expensive but it's metal and has a built-in swivel.


I have the 1100 and it works fine, but screwing it on is kind of a PITA because there's no swivel in the hose. The 1109 would be a nice upgrade.
 

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Actually, in looking at the options I'd suggest spending a little more and getting the 1109. Bit more expensive but it's metal and has a built-in swivel.


I have the 1100 and it works fine, but screwing it on is kind of a PITA because there's no swivel in the hose. The 1109 would be a nice upgrade.
IMG_5334.jpeg


Thank you for suggestions! Happy to report I already have the 1100 for Miata.
I added an air line coupler to avoid the hassle of no swivel you mention.
 

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From experience :sneaky: Make sure you have returned the callipers to correct side. Bleed nipple needs to be on top. If it is the bottom, you bleed till the cows come home but you will never remove all the air.
 
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