Spongy Brakes

spankle my wankle · 01-16-2010, 04:12 PM

My 85 has really spongy breaks and I just wanted to bounce ideas out and see if what I think is the problem is, is really the problem. The pedal travels about an 1"-1 1/2" before catching hard, I've replaced the master cylinder and the calipers and brake pads so im thinking that its the power booster. I know normally the breaks get harder when the power booster goes out but when I pump the breaks the idle stumbles. This leads me to think that maybe theres a vacuum leak at the seal or something and its not building enough vacuum. Any ideas?

My5ABaby · 01-16-2010, 04:21 PM

Give it to me. It's 100% broken.

spankle my wankle · 01-16-2010, 06:19 PM

give what to you?

djmtsu · 01-16-2010, 07:33 PM

He is saying that your car is broken, so you should just give it to him and don't bother trying to fix it.

Come on Seth, you are no stranger to sarcasm!

I would bet it is the booster. I can look and see if the local yard still has the FB that was there last time.

Also, have you checked the fluid level? What color is the brake fluid? Any leaks at the calipers/hoses?

My5ABaby · 01-16-2010, 08:26 PM

Quote:

Originally Posted by djmtsu

He is saying that your car is broken, so you should just give it to him and don't bother trying to fix it.

Come on Seth, you are no stranger to sarcasm!

spankle my wankle · 01-17-2010, 03:39 PM

I understand sarcasm I just didnt think someone would post something so ridiculous and not follow it up with some advice. So i thought maybe he wanted a broken power booster, idk people are weird now he could be one of those hoarders you see on tv.

I just bled the system completely with new fluid, and no leaks. The only other thing I could think of is the proportioning valve cause when I brake real hard it kicks to the right so much that it turns the steering wheel. Yea tell me if its there and what condition its in I need some other stuff too. Thanks.

spankle my wankle · 01-17-2010, 04:05 PM

the reason I dont think its the valve though is the the whole system bleeds fine. Another thing is that I can pump the brakes and it will get better.

My5ABaby · 01-17-2010, 04:07 PM

Quote:

Originally Posted by spankle my wankle

I understand sarcasm I just didnt think someone would post something so ridiculous and not follow it up with some advice. So i thought maybe he wanted a broken power booster, idk people are weird now he could be one of those hoarders you see on tv.

I just bled the system completely with new fluid, and no leaks. The only other thing I could think of is the proportioning valve cause when I brake real hard it kicks to the right so much that it turns the steering wheel. Yea tell me if its there and what condition its in I need some other stuff too. Thanks.

I'd only do it to someone local.

dudemaaan · 01-17-2010, 04:37 PM

Do the brakes feel spongy when the car is off? Usually spongy brakes is air left in the system.

Rogue_Wulff · 01-17-2010, 04:39 PM

Sounds to me like you have air in the system still, a sticking caliper, or a brake hose that is bad.
Silly question, but does the car have drum or disc on the rear? You didn't specify, just stated that calipers and pads had been replaced.
If the rear is drum, the shoes being a bit out of adjustment will cause the pedal to feel spongy and low on the first try, but will pump up on the second hit.
A bad booster will have no effect on how far the pedal travels, only the effort needed to push the pedal down. The only way a booster can have any effect on pedal travel, is the plunger inside it that actually operates the master cyl. It could be out of adjustment, but that is something normally found only after a replacement booster has been installed.

Rogue_Wulff · 01-17-2010, 04:48 PM

Oh, and since you say it pulls hard to the right when braking, I'd start by bleeding the hell out of the left front. That caliper is fed directly by the MC, totally bypassing the proportioning valve. The location of the port feeding the LF (bottom front of MC) makes it darned hard to get all the air out if the MC is not fully bench bled prior to installation.

spankle my wankle · 01-17-2010, 08:17 PM

Ill go back and rebleed everything and see what happens. It is drum and I've never taken a look back there so Ill pull off the cover and see if any adjustments need be done. The thought that I have now is it must either be air or serious lack of brakes in the back and that forces more fluid to the right front caliper causing the pull. Thanks roque

jfaplanet · 01-17-2010, 10:17 PM

Parks 80 LS was spungy till we bleed the master cyl again. Now its good and stiff. Does the 85 have a bleeder on the side of the master?

spankle my wankle · 01-17-2010, 11:32 PM

not that im aware of but ill check and see

Rogue_Wulff · 01-18-2010, 12:41 AM

I'd bet on 1) air in the LF, and possibly 2) rears needing adjusted. The rear self adjusters can freeze up if they are not properly lubed and/or the car sits for a while.

01-16-2010, 04:12 PM	#1
spankle my wankle Rotary Fanatic Join Date: Feb 2008 Posts: 185 Rep Power: 18	Spongy Brakes My 85 has really spongy breaks and I just wanted to bounce ideas out and see if what I think is the problem is, is really the problem. The pedal travels about an 1"-1 1/2" before catching hard, I've replaced the master cylinder and the calipers and brake pads so im thinking that its the power booster. I know normally the breaks get harder when the power booster goes out but when I pump the breaks the idle stumbles. This leads me to think that maybe theres a vacuum leak at the seal or something and its not building enough vacuum. Any ideas?

01-16-2010, 04:21 PM	#2
My5ABaby Sigh..... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 2,377 Rep Power: 20	Give it to me. It's 100% broken. __________________ 1986 Sport: 132k miles, 5A (Sapphire Blue Metallic), Tokico Blues, Racing Beat Springs, Custom LED tailights (only S4 LED tails in the world), SSR Mark II, Racing Beat exhaust, S5 black interior, Rotary Resurrection rebuild at 120k miles Community Service Manual RotorWiki "Imagination costs nothing; we could build square locomotives or fly to Mars" - Felix Wankel Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the "present."

01-16-2010, 07:33 PM	#4
djmtsu My minds tellin' me no... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 4,043 Rep Power: 22	He is saying that your car is broken, so you should just give it to him and don't bother trying to fix it. Come on Seth, you are no stranger to sarcasm! I would bet it is the booster. I can look and see if the local yard still has the FB that was there last time. Also, have you checked the fluid level? What color is the brake fluid? Any leaks at the calipers/hoses? __________________ 1976 Mazda Cosmo RX-5 1976 Mazda Cosmo RX-5 2003 Toyota Tundra TRD 2015 Toyota 4Runner SR5

01-17-2010, 04:37 PM	#9
dudemaaan Rotary Fanatic Join Date: Mar 2008 Location: Brenham, TX Posts: 335 Rep Power: 18	Do the brakes feel spongy when the car is off? Usually spongy brakes is air left in the system. __________________ 500+ HP thanks to: Fast reacting IAT sensor thread! Mechanical Pre-turbo Water Injection Thread Dual Stock fuel pumps Thread T2 differential swap!

01-17-2010, 10:17 PM	#13
jfaplanet Rotary Fanatic Join Date: Feb 2008 Location: Smyrna, TN Posts: 134 Rep Power: 18	Air Parks 80 LS was spungy till we bleed the master cyl again. Now its good and stiff. Does the 85 have a bleeder on the side of the master?

01-16-2010, 06:19 PM	#3
spankle my wankle Rotary Fanatic Join Date: Feb 2008 Posts: 185 Rep Power: 18	give what to you?

01-17-2010, 03:39 PM	#6
spankle my wankle Rotary Fanatic Join Date: Feb 2008 Posts: 185 Rep Power: 18	I understand sarcasm I just didnt think someone would post something so ridiculous and not follow it up with some advice. So i thought maybe he wanted a broken power booster, idk people are weird now he could be one of those hoarders you see on tv. I just bled the system completely with new fluid, and no leaks. The only other thing I could think of is the proportioning valve cause when I brake real hard it kicks to the right so much that it turns the steering wheel. Yea tell me if its there and what condition its in I need some other stuff too. Thanks.

01-17-2010, 04:05 PM	#7
spankle my wankle Rotary Fanatic Join Date: Feb 2008 Posts: 185 Rep Power: 18	the reason I dont think its the valve though is the the whole system bleeds fine. Another thing is that I can pump the brakes and it will get better.

01-17-2010, 04:39 PM	#10
Rogue_Wulff Non Member Join Date: Jun 2008 Posts: 310 Rep Power: 18	Sounds to me like you have air in the system still, a sticking caliper, or a brake hose that is bad. Silly question, but does the car have drum or disc on the rear? You didn't specify, just stated that calipers and pads had been replaced. If the rear is drum, the shoes being a bit out of adjustment will cause the pedal to feel spongy and low on the first try, but will pump up on the second hit. A bad booster will have no effect on how far the pedal travels, only the effort needed to push the pedal down. The only way a booster can have any effect on pedal travel, is the plunger inside it that actually operates the master cyl. It could be out of adjustment, but that is something normally found only after a replacement booster has been installed.

01-17-2010, 04:48 PM	#11
Rogue_Wulff Non Member Join Date: Jun 2008 Posts: 310 Rep Power: 18	Oh, and since you say it pulls hard to the right when braking, I'd start by bleeding the hell out of the left front. That caliper is fed directly by the MC, totally bypassing the proportioning valve. The location of the port feeding the LF (bottom front of MC) makes it darned hard to get all the air out if the MC is not fully bench bled prior to installation.

01-17-2010, 08:17 PM	#12
spankle my wankle Rotary Fanatic Join Date: Feb 2008 Posts: 185 Rep Power: 18	Ill go back and rebleed everything and see what happens. It is drum and I've never taken a look back there so Ill pull off the cover and see if any adjustments need be done. The thought that I have now is it must either be air or serious lack of brakes in the back and that forces more fluid to the right front caliper causing the pull. Thanks roque

01-17-2010, 11:32 PM	#14
spankle my wankle Rotary Fanatic Join Date: Feb 2008 Posts: 185 Rep Power: 18	not that im aware of but ill check and see

01-18-2010, 12:41 AM	#15
Rogue_Wulff Non Member Join Date: Jun 2008 Posts: 310 Rep Power: 18	I'd bet on 1) air in the LF, and possibly 2) rears needing adjusted. The rear self adjusters can freeze up if they are not properly lubed and/or the car sits for a while.