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91 CRX DX
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226 Posts
Discussion Starter #1
Hello DSO
I have a 91 CRX dx, I noticed at stops I had to press the pedal closer to the ground, the longer I sat, so I bled my brakes, in the order stated in the FSM, and my pedal firmness has gone to shit, I had no air coming out before I closed the bleeder. Is my master cylinder gone bad?
 

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Classic Man
Civic
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16,355 Posts
Bad MC. The fluid bypasses the cup seal slowly.

The harder you press, the less it should fall down.

If you just barely press the pedal, but apply force, it will probably sink faster than pushing hard on the pedal. Very good sign the cup seals are toast in the MC.
 

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91 CRX DX
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226 Posts
Discussion Starter #6
It's a good reason to bleed the brake system. Don't forget to bench bleed the new MC


The RAYBESTOS MC39968 (MC39968:p) MC I used was a POS and leaked right away, but the CENTRIC item 13040016 (130-40016) has been great for the last year and a half. Both are the 15/16" master cylinders.

I don't think I need a 15/16" master cylinder with stock dx brakes, and to make matters worse, my driver rear hard line ruptured so I'm waiting on a tow truck :(
 

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BATSLOMAN GIVES NO FUCKS.
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dumb question, when you bench bleed it, you still have to take the fittings off and install the brake lines. don't you defeat your purpose because youre letting air back into the system? isn't it easier to just bleed it all at once?
 

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Black/Green Civic HB
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753 Posts
Bench bleeding makes it much easier!
Did this about 2 months ago, not bench bleeding will give you a lot more air to work out of the whole brake system when bleeding.
 

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Classic Man
Civic
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16,355 Posts
Quite a bit of bubbles should come out. I would go ahead and keep bleeding, making sure to follow the correct bleed sequence for your car. They do have diagonal braking systems so its not furthest from the MC to closest like most old cars.

Make sure to push the pedal down fairly slowly... not slowly, but not quick. If you push too fast/with too much force it can create bubbles in the system. Let up slow as well if you are using a 1 man bleeder kit. Otherwise air can bypass the threads on the bleeder screw and you are back to square one.
 

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91 CRX DX
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226 Posts
Discussion Starter #12 (Edited)
Ok, I'll keep that in mind tomorrow, also on the front calipers when you break the bleeder open, does just the nut turn, or the whole screw?

I tried bleeding it yesterday and I had a few small bubbles in the corner where I replaced the line, but no others corners even moved fluid or air, the level never dropped in the MC.
 

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Premium Member
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537 Posts
dumb question, when you bench bleed it, you still have to take the fittings off and install the brake lines. don't you defeat your purpose because youre letting air back into the system? isn't it easier to just bleed it all at once?
Bench bleeding clears the air out of the master cylinder not the lines. It ensures that you are pumping fluid and not air into the brake lines.
 
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