Car: '96 Accord LX Sedan Auto
IMPORTANT: I changed the standard front and rear brakes. The front breaks I coverted to ROH (rotor over hub) using 2000 Accord V6 calipers (the same as Prelude VTEC calipers) and 11.1" rotors. The rear brakes I converted from drum to the '95 Accord EX disk brakes. This setup has been running fine for 1.5+ years.

Ok, I was driving along and all of a sudden when I tried to brake my petal went almost to the floor before the car seemed to slow down a little. Pumping the brakes gave me a little more pressure to stop. Ok, I get the car home, check for leaks at the four calipers and didn't see anything unusual. I decide to change out the master cylinder. When I removed the MC, I heard this slight sucking sound which I thought was kinda odd. Anyway, I bench bled the new MC install it and then bleed the brakes. Before I start the car, I press the brake pedal and it doesn't have pressure. I have to press the brake pedal like six times before it gets hard (usually only takes 2-3 times). Anyway, I go for a test drive and the brakes seem kinda soft but they appear to be working, but then all of a sudden the same thing brakes to the floor.

Could it be the brake booster or vacuum leak? How can I test?

Please help!

Edit: I changed the MC again with a new one instead of a reman. Brakes are still soft. Brake pedal didn't get hard even after about 10 pedal pumps. This is without the car running. Then I started the car up and pumped the pedal a few times and it got firm. Then I turned the car off and pressed the pedal and it was pretty firm like it normally does when the car is off. Another weird observation is that I am hearing this high pitched 'whistle' when I pump the brakes.

 

Did you notice any brake fluid leaking from the master when you removed it?

It's very common for the secondary seals to leak, causing the pedal to drop to the floor.

The sucking sound you heard was the release of pressure from the booster

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Evs-One &raquo;</TD></TR><TR><TD CLASS="quote">Did you notice any brake fluid leaking from the master when you removed it?

It's very common for the secondary seals to leak, causing the pedal to drop to the floor.
</TD></TR></TABLE>

No, I didn't. But what about the two new MC I have tried?

 

Did you bleed your ABS system as well? Any leaks around your ABS mod?

 

No ABS on this car.

 

Anybody?