Lo-Buck EF

So, I'm having a brake issue. Long story short-my brake pedal has a huge ammount of travel (goes to the floor.)
So far I've replaced rear calipers and pads, front rotore, soft lines, master (3x) and the booster once. No leaks anywhere, no air when I bleed the system bench bled the masters before instalation, the rod length on the booster is also set right.
Any ides?

DB2-R81

You didn't start off with a long pedal, or is this a new build, what changed to get you there? Did it come on gradually? After a fluid change? After a pad or hardware change? Worse under certain weather/temperature conditions? Is your system stock or have you made changes to the stock system? Provide us some clues to work with!

Lo-Buck EF

Eg si, itr front calipers, teg rear, 1" da master, dc2 booster, brand new lines.
This car is a new build for h2. The pedal was good for the first test day. But after the first race the pedal was crappy. The old rear calipers were frozen so I changed them and the rear pads.blead it and couldn't get a pedal.

lwnslw

You already change just about everything and I'm sure you know what you're doing so do you have any leaks? . I must think you don't. If you have a long pedal and no leaks is either master or air in the line. Regardless of what kind of lines, fluid or calipers. The booster only gives u vacuum assistance and is external. I know you change the booster 3 times.
How did you bleed the brakes. Did you start with the passanger rear?

night

all original line routing? no high spots?
do you have a solid pedal at the end of its travel, or none at all ever?

lwnslw

Let me ask this, did you bleed all the system after changing rear calipers?. I know they sound like silly questions but your problem has to be looked from all angles

MBellRacing

...silly question...

Are you 100% certain that all the parts are the right volumes? Did any of the parts you changed come in a larger volume or something for a different car? I have actually done this before and it just completely changes the ratio for input to output on the hydraulics.

Lo-Buck EF

Yes, I blead all 4 corners after the caliper change. I think that day I bled them at least 3 times.

I did not change any parts to a different size. The booster and master are larger than stock, but the brakes were great when I first put this chassis together.

Here's another bit of info. When the car is off or the booster is unhooked from its vac source, the pedal is firm. But as soon as you apply vac to the booster the pedal goes to the floor. We tried pinching off the line thinking the booster might be getting too much vac for some reason, but that didn't do anything. I also tried driving without the booster connected but I can't race it like that.

smokin rubber

where is the mc from, I had a autozone mc and the pedal travel was cut in half with a new honda mc

Lo-Buck EF

I have one master from rock auto (new), one from the zone (reman). Both yielded the same results. The booster was from the local junk yard. Also yielded the same results.
All the hard lines are in good shape. No kinks, no leaks, no weaping fittings.
As far as the pedal pressure, if I roll down the driveway the brakes engage where they should. But when you apply any kind of pressure the pedal goes to the floor. It has very little if any pressure down at the bottom.

FerreiraCompetitions

Sorry to tell you this man, but I deal with these types of things almost daily and its always air. You just have to rebleed everything, if the pedal doesnt get hard no matter what (and all components are new), then its air in the system, period. Best option is to let the car gravity bleed (overnight if need be), put some pans under the calipers or bleeder bottles in each caliper and just let it sit. Make sure the fluid is always above the line at the reservoir.

slammed_93_hatch

gravity bleed.

Crack all of the bleed screws and let them set for 3 or 4 hours, or even over night.


It works great.

FerreiraCompetitions

Yup, I take it you've run around in circles because of that too. All racers, sooner or later do.

Lo-Buck EF

Ya know, I thought of doing this (letting it gravity bleed all night). Ill try it tonight when I get home and see what I come up with.

Lo-Buck EF

the pedal is firm when the car is off. if i had air, wouldnt the pedal be spongy with the car off also?

lwnslw

I'm with Ferreira, has to be air in the system, you feel the problem more with the mc but you still have the problem with out it. Let us know tomorrow

Drive 4 fun

This seems correct, so if it is air, explain. Soft pedal is usually air, but I would like to understand this one. Is the thought that leg without booster, motor off, will not push hard enough to feel air???

Lo-Buck EF

i drove it w/o the booster. so if there were air, i'd feel it trying to stop the damn thing.

night

try bench bleeding the master again on the car. with help.. just loosen the lines, pedal down slow then tighten them and that can help a lot. a master that doesn't get bench bled enough can be a bitch to bleed out far enough at the wheel.

Lo-Buck EF

tried that last week. no good.

night

doh

lwnslw

as I understand it and correct me if I'm wrong, the booster is a separate system from the hydraulic system. They both work together but are separate systems. So even if you don't have a booster the hydraulic will still work , it wil be very hard to push by itself but still work. Just for the heck of it how bout that check valve in the hose going into the booster. But again lo-buck I really think there is air in the hydraulic system.
Either way I hope you find the solution. Are u going to Nats? Maybe you can tell me what happened.

Lo-Buck EF

no nats for me. the car has been down for months. i only got one race on this chassis so utah is out.
i have another check valve comming even tho the one in my car checks out.
i have bled 5 gal of fluid through this car. there is no air in it.

STN_Pat

i had this problem once, the front calipers were inverted...the hose was higher than the bleeder. I know it sounds obvious but it wasn't.

Also, with all 4 hose pinched, it still is low ? I'd try another master, and make sure all of the hoses are perfectly good (talking about the flaring on the master).

good luck

Lo-Buck EF

i checked that. calipers are on correctly.
all the flairs are good (as far as i can tell) but when i change this booster again, im ognna check again and make sure the angles are right.