Spongy brakes

firzen · 10-15-2008, 02:13 PM

Hey all- got a question about my brakes. I recently rebuilt my entire brake system for my S5 T2, save the master and booster. Bled all four corners and the ABS until it the fluid was bubbleless and clear as day. Checked to see if nothing leaked or broke. Unfortunately, the whole thing is still spongy like a marshmallow.

Any tips and hints? I suspect it could be air in the master cylinder or booster but am not too sure how to go about getting the air out. I'm due for a state safety inspection soon and would like some feedback before I send it in.

Thank you.

10-15-2008, 02:23 PM

sounds like either air in the system (back by the prop valve) or you have an inner seal on the brake master leaking..

I would do a gravity bleed for about 20 minutes per wheel and see if that helps, otherwise go back to every connection and make sure there is no leaks anywhere..

is the pedal spongy with the car on or with the car off or both?

could be a weak booster also.. another thing to check is the hose that goes from the booster to the intake.. make sure all of those connections are good and the hoses are in good shape.

Whizbang · 10-15-2008, 02:28 PM

seems like the mazda love to eat master cylinders. i would look there.

firzen · 10-15-2008, 02:35 PM

Quote:

Originally Posted by SpooledupRacing

sounds like either air in the system (back by the prop valve) or you have an inner seal on the brake master leaking..

I would do a gravity bleed for about 20 minutes per wheel and see if that helps, otherwise go back to every connection and make sure there is no leaks anywhere..

I did that, twice, just to be sure.

Quote:

Originally Posted by SpooledupRacing

is the pedal spongy with the car on or with the car off or both?

Both. It's already soft as heck when it's not on and when the booster kicks in when it's on, the pedal almost bottoms out.

Quote:

Originally Posted by SpooledupRacing

could be a weak booster also.. another thing to check is the hose that goes from the booster to the intake.. make sure all of those connections are good and the hoses are in good shape.

Are you talking about the check valve when you say booster to intake hose? Haven't checked that yet but I will take a look later today...

Quote:

Originally Posted by Low Impedance

seems like the mazda love to eat master cylinders. i would look there.

I was afraid it would either be a booster or MC problem... Worst comes to worst, I'll redo the whole system and grab the 929 master while I'm at it. Will do a write-up if it ever goes that far...

Thanks.

BLKTOPTRVL · 10-15-2008, 02:37 PM

Were the brakes done in the proper order?

10-15-2008, 02:42 PM

in my experience if u bleed the system 2 times all around order dont mean anything really..

I have a stong feeling it is master cylinder since they are notorious..

if u need one let me know I got them for a good price (or try to)

firzen · 10-15-2008, 03:03 PM

Quote:

Originally Posted by BLKTOPTRVL

Were the brakes done in the proper order?

Yes.

Quote:

Originally Posted by SpooledupRacing

in my experience if u bleed the system 2 times all around order dont mean anything really..

I have a stong feeling it is master cylinder since they are notorious..

if u need one let me know I got them for a good price (or try to)

Curses.

I'll take it to a shop and have them try bleeding the MC first then. Hopefully that will take care of the problem. If not, then we'll go from there.

Nopis1O · 01-21-2009, 11:58 AM

so what happened? i have the same problem only i replace the master and the booster also. i have bleed my breaks every possible way the still feel soft. The weird thing is on my sometimes they work perfect sometimes the suck which makes it really hard to autocross. any way thinking about getting an after market MC and going from there.

NEED UPDATE!!

firzen · 01-21-2009, 12:26 PM

I haven't gotten around to bleeding the MC yet but apparently the shop said that the brakes were OK. Heck, they even passed inspection.

I do intend to rebleed them come a few months as it is friggin cold where I'm at and I don't drive my car during winter months anyway.

If I were you and my brakes were that bad, I would not autocross just for safety reasons.

10-15-2008, 02:13 PM	#1
firzen Rotary Fanatic Join Date: Mar 2008 Posts: 231 Rep Power: 18	Spongy brakes Hey all- got a question about my brakes. I recently rebuilt my entire brake system for my S5 T2, save the master and booster. Bled all four corners and the ABS until it the fluid was bubbleless and clear as day. Checked to see if nothing leaked or broke. Unfortunately, the whole thing is still spongy like a marshmallow. Any tips and hints? I suspect it could be air in the master cylinder or booster but am not too sure how to go about getting the air out. I'm due for a state safety inspection soon and would like some feedback before I send it in. Thank you.

10-15-2008, 02:28 PM	#3
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp Posts: 3,190 Rep Power: 20	seems like the mazda love to eat master cylinders. i would look there. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

10-15-2008, 02:37 PM	#5
BLKTOPTRVL Rotary Fanatic Join Date: Feb 2008 Posts: 192 Rep Power: 18	Were the brakes done in the proper order? __________________ ...shoot a mother-humpin moose, eight days of the week...

01-21-2009, 11:58 AM	#8
Nopis1O Rotary Fanatic Join Date: Apr 2008 Location: Mid State Illinois Posts: 159 Rep Power: 18	so what happened? i have the same problem only i replace the master and the booster also. i have bleed my breaks every possible way the still feel soft. The weird thing is on my sometimes they work perfect sometimes the suck which makes it really hard to autocross. any way thinking about getting an after market MC and going from there. NEED UPDATE!! __________________ 1988 Fc Vert. Super Stock 1990 Fc Hard top: Brideported 13b, weber carb, 350z wheels w/nitrogen, or 16in BBS meshies, Msd, Racaro Racing Seats, Custom Gauge cluster, custom Intake, Relocated Battery, 3inch header back borla exhaust system, Alpine stereo system, Wire tucked, S4 shift boot&knob, custom Strut bar, And soon to come a Full black w/ gold pearl paint job, powder coated break calipers, all black interior, bride headliner/door panels.

10-15-2008, 02:23 PM	#2
SpooledupRacing Guest Posts: n/a	sounds like either air in the system (back by the prop valve) or you have an inner seal on the brake master leaking.. I would do a gravity bleed for about 20 minutes per wheel and see if that helps, otherwise go back to every connection and make sure there is no leaks anywhere.. is the pedal spongy with the car on or with the car off or both? could be a weak booster also.. another thing to check is the hose that goes from the booster to the intake.. make sure all of those connections are good and the hoses are in good shape.

10-15-2008, 02:42 PM	#6
SpooledupRacing Guest Posts: n/a	in my experience if u bleed the system 2 times all around order dont mean anything really.. I have a stong feeling it is master cylinder since they are notorious.. if u need one let me know I got them for a good price (or try to)

01-21-2009, 12:26 PM	#9
firzen Rotary Fanatic Join Date: Mar 2008 Posts: 231 Rep Power: 18	I haven't gotten around to bleeding the MC yet but apparently the shop said that the brakes were OK. Heck, they even passed inspection. I do intend to rebleed them come a few months as it is friggin cold where I'm at and I don't drive my car during winter months anyway. If I were you and my brakes were that bad, I would not autocross just for safety reasons.