Recently I posted about my problem with my brake pedal sinking only sometimes, but not other times:

https://honda-tech.com/zerothread?id=848354

And today another person posted the exact same problem w/ the brakes on his DA:

https://honda-tech.com/zerothread?id=857424

So I was thinking about it today, and I'm wondering, when the brake pedal starts to sink, where does the extra displaced fluid go? I looked at my reservoir (w/ Nintendo sock on it ) and I see no signs of any fluid coming out through the cap. I also looked underneath the dash and I see no signs of any fluid leaking down the firewall onto or under the carpet. Also my brake fluid level is still at the max top line on the reservoir. So where does the fluid go when the brake pedal starts to sink when I'm at a stoplight or whatever?

 

There's 3 sets of seals in the MC. The primary piston & secondary piston each have seals. Think of them like the plungers in a bicycle tire pump. They act kinda like a check-valve. The 3rd seal is around the shaft in the back of the MC.

When you press the brakes, the piston seals push fluid out into the brake lines. But there's ALSO fluid behind those pistons, too. The shaft seal keeps it from leaking out. This space behind is connected to the reservoir, so it never gets high-pressure like the brake lines see.

When the pedal sinks, the fluid is seeping around the piston seals. So while the pedal sinks, the fluid bypasses around the pistons into the space behind the pistons. It doesn't leak out, because the shaft seal is still OK. When you release the pedal, the piston seals do their check-valve thing, so the fluid doesn't 'go' anywhere.

 

So a new MC will fix this problem, right?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PatrickGSR94 &raquo;</TD></TR><TR><TD CLASS="quote">Recently I posted about my problem with my brake pedal sinking only sometimes, but not other times:
</TD></TR></TABLE>

I have this exact same problem.. however i never thought about posting it.. [dummy] .. So this a problem with the seal..? and like ^^^ said.. will new MC fix it??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PatrickGSR94 &raquo;</TD></TR><TR><TD CLASS="quote">So a new MC will fix this problem, right?</TD></TR></TABLE>Yep. Just like I told you a week & a half ago...