Bird333

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 bleed 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!

Car: '96 LX Sedan Auto

gqstatus05

Did you check your brake fluid reservoir?

gqstatus05

Did you bleed the brakes by yourself. I thought you needed 2 people to bleed the brakes. One person to pump the brakes another to bleed them.

fit4jenn

if its the booster, your brake pedal will be very hard, requiring more effort to depress. sinking pedal indicates brake master cyl. make sure you bleed all the air out of the brake system

JDM_DC4_Fanatic

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fit4jenn &raquo;</TD></TR><TR><TD CLASS="quote">if its the booster, your brake pedal will be very hard, requiring more effort to depress. sinking pedal indicates brake master cyl. make sure you bleed all the air out of the brake system</TD></TR></TABLE>


Your right about the booster, but a sinking pedal isnt ALWAYS a BMC. Granted, that is usuially the problem, but it could also be a leaking caliper, or wheel cylinder.

Bird333

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gqstatus05 &raquo;</TD></TR><TR><TD CLASS="quote">Did you bleed the brakes by yourself. I thought you needed 2 people to bleed the brakes. One person to pump the brakes another to bleed them. </TD></TR></TABLE>

I have a vacuum pump I am using.

Bird333

After bleeding the brakes again, I had to pump my pedal 6-8 times again to get it firm. I noticed a hissing/air leak sound each time I pumped the pedal (until it got firm that is). Is this normal? I don't recall hearing this on other occasions. One thing that has really got me stumped in this is that I can't seem to find any brake fluid leaking anywhere.

Ideas?!

gqstatus05

They had a trick while bleeding the brakes. You get a hose and submerge it in I guess brake fluid and pump your breaks. If you see bubbles coming up you still have air. I forgot how it went maybe someone can elaborate.

mad matt

I know this is an old post but I figured if I am reading them for answers other may be too.this didn't answer my question but i can answer some here.
First low soft pedal with no leaks and no air in the lines.Check the caliper slides.If they stick off center one pad will have to travel farther to contact the disk.more travel in the pad, more fluid needed in the caliper,more pedal needed to to push more fluid.
Second self bleeding with a jar.Old shade tree mechanic trick.use clear tube tight fitting on the bleeder valve.apply lithium grease to bleeder threads to help air tight seal.run the tube into a jar with the end submerged under one inch of fluid.crack the valve open just slightly.slowly push down on the pedal and let it lift quickly.when lifting the path of least resistance is drawing from reserve not the cracked open bleeder.when you get a solid flow with no bubbles for a few cycles you are good.Don't let reserve run dry and run twice the volume of reserve through each line to ensure you got all the air out.
hope it helps someone

ScottGerald

I had the same issue with my Accord. Pedal to the floor and all of that. I replaced the MC (including bench bleed and bleed MC again once installed,), replaced a caliper (wasn't getting any fluid out of it), and bled each corner. Left front and right rear bleed fine but right front and left rear don't. I was using the hand pump bleeder on left rear. I pumped up the bleeder to about 25 psi and opened the bleeder screw and I heard this sucking sound which seemed to be coming from the engine compartment. I wasn't seeing any puddling under the car or in the engine compartment. Any ideas what that could be?

Willis2K

If you still have the inserts and lines from the purchased master cylinder. Disconnect the brake lines and with a second person dip the lines in a half full bottle of brake fluid.

Pump the brakes until all bubbles are removed. Reconnect lines then proper procedure to bleed is starting at right rear. Have someone pump the breaks until firm and hold it. Open bleeder valve and when pedal hits the floor close bleeder valve. Repeat until all air is out of that line.

Check your master cylinder. Make sure it's full and go to left rear. Repeat same procedure. If all air is out go to right front. Do the same and then left front. Pedal should be nice and firm.