I have been trying for hours to bleed the brakes on my ITR, I get a great pedal feel but when I start the engine the pedal sinks to the floor

Anyone had this problem and did you manage to fix it?

Thanks for any help.

 

Do you pump the brakes when you turn the car on?

You get pressure by doing this.

 

I have tried manually bleeding the system and presure bleeding it.

If I start the car with presure on the pedal as the car fires up then the pedal will drop to the floor.

If I pump the pedal with the engine running it doesn't get any better.

If I then stop the engine and pump the pedal the firm feeling returns.

Should I be doing anything with the ABS?

 

I had the exact same problem. My master cylinder was bad. After replacing the MC, I installed speedbleeders and the brakes now feel great.

 

master cylinder is probably owned. Sometimes when bleeding the brakes the seals will get f'd up by the piston if your floor the pedal. Usually you're fine, but sometimes not. I've changed more than one MC because of this.

 

Should I be doing anything special with regard the ABS system whilst I bleed the brakes?

 

I think what Dave and Batouttahell are saying is that you may have a bad Master Cylinder.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris N &raquo;</TD></TR><TR><TD CLASS="quote">I think what Dave and Batouttahell are saying is that you may have a bad Master Cylinder.</TD></TR></TABLE>

lol exactly. Get that bad MC replaced and you'll be Doplonkin'

 

I want to rule out EVERYTHING else before I start swapping out bits.

Thanks for the opinions though, keep them coming.

 

IMO, that is the only option at this point.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FizzleDaKlown &raquo;</TD></TR><TR><TD CLASS="quote">master cylinder is probably owned. Sometimes when bleeding the brakes the seals will get f'd up by the piston if your floor the pedal. Usually you're fine, but sometimes not. I've changed more than one MC because of this.</TD></TR></TABLE>

yep, yep... that's true. rust builds up in the bottom portion of the MC bore you don't usually use when your brakes are working properly. when you bleed the brakes and push the pedal down to the floor, you push the MC piston all the way down into the bore, ripping the seals on the piston. I've seen this happen a few times, too.

to avoid damage to the MC, put something to block the brake pedal from going down any further than it would under normal application of your brakes. I tape some short 2x4 blocks together and put that under the brake pedal. That way, when I step on the brake pedal to bleed, I limit the travel of the piston in the MC so it dosn't get damaged.

so yeah... sorry to say, it sounds like your MC needs to be changed or rebuilt.

 

Ok, looks like i'll be changing the MC. Do you guys know of any procedure for cycling the ABS whilst bleeding? (I work as an equipment engineer for Honda UK in the Swindon factory, when they are factory filled we evacuate it then fill, but we cycle the ABS whilst it fills.)

 

Haynes says the ABS has its own bleed valve, but I have never found it. Some people suggest that bleeding while the car is running helps to purge the ABS lines, but it depends who you ask. I did a plain-jane bleed (with speedbleeders) of the entire system, used only 1/2 liter of superbl00 and my brakes have never felt better.

Edited: Haynes, not Helms, refers to the ABS bleed valve.


Modified by Batoutahell at 9:37 PM 7/2/2003

 

Crud, I might've blown my MC out then, I always pushed the pedal to the floor when I bled the brakes, and it definitely felt firmer when I originally bought it...

 

I am glad I read this post...good luck on your brakes bud.

 

Did you change the pads too? Turn the car on, and pump the pedal a few times. If you're not getting any pressure, then the MC is probably gone.

Never press the pedal all the way down.

Warren

 

Okay, so let's assume the MC is gone. Can some one expalin what is happening when the car is running to cause the pedal to sink, but pressure can be built up with the car off? Just curious.

 

power brake booster acts as a pressure amplifier when the car is running. when you push on the brake pedal with the car off, very little pressure is being applied to the MC, so it requires more effort to push the MC piston in.

With the car running and the booster amplifying the pedal pressure, the MC piston is pushed into the bore with a much greater force pushing the brake fluid past the seals and pedal goes to the floor.

ever try using the brakes on a power brake car when it is being towed and your engine is off? It takes much more pedal pressure to apply the brakes due to the power booster not assisting.


http://www.howstuffworks.com/power-brake.htm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Warren &raquo;</TD></TR><TR><TD CLASS="quote">Never press the pedal all the way down.

Warren</TD></TR></TABLE>

Just curious. What if one installs a new MC and bleeds regularly with pushing the pedal to the floor - will that part of the m/c bore get "used" enough to not warrant rust and worrying about it?

RJ

 

Is there any way other than by feel to identify whether or not the MC has gone bad? And what RJ said...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by typer03260 &raquo;</TD></TR><TR><TD CLASS="quote">I have been trying for hours to bleed the brakes on my ITR, I get a great pedal feel but when I start the engine the pedal sinks to the floor

Anyone had this problem and did you manage to fix it?

Thanks for any help.</TD></TR></TABLE>

I am having this same exact problem.

Did changing the master cylinder help the problem?