Problem with brakes (spongy when engine running)

[jase ek]

hey ppl

i dunno wat im doing wrong, i bled all the brakes till a nice stream of fluid coming out of nipple
then started the car and the pedal was very spongy, i check the one way valve and thats fine also the vacum booster line..
what else could this be ? i hear you can still use stock booster/mc for ca18 front brakes..
imm pretty sure i got most air out, should i bleed them again ?
the pedal is ok firm when engine is off.. not as firm as should be tho...

any input would be appreciated..

thanks

[Jonny Rochester]

Tell us the diameter of the brake piston in the CA18 brakes, then tell us the diameter of the brake piston in the AE86 brakes. If the CA18 piston is bigger, then idealy you want the master cylinder to be proportionaly bigger as well to maintain the same firmness and pedal travel.

[Wanabe_Garage]

Well when I was bleeding my brakes I left the handbrake up... and i didnt get a firm feel or suffiecent handbrake on a slope

I doubt you would make such a silly mistake

[Dongaz]

Thats weird as I have changed to the series 5 rx7 calipers and 280mm discs and I still have std lines and m/c and I have decent pedel feel. It could be better but under no circumstances has it been spongy. The nissan m/c will be changed over a lil later. Oh and I havent ever had brake fade and thats under track conditions at a sprint and going up and down nebo.

[ke70dave]

<div class='quotetop'>QUOTE (Dongaz @ Nov 29 2007, 02:29 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=443927)</div>
Thats weird as I have changed to the series 5 rx7 calipers and 280mm discs and I still have std lines and m/c and I have decent pedel feel. It could be better but under no circumstances has it been spongy. The nissan m/c will be changed over a lil later. Oh and I havent ever had brake fade and thats under track conditions at a sprint and going up and down nebo.[/b]

simliar for me as well

i have cefiro brakes (slightly bigger than CA i hear) with standard mastercylinder,and no spongyness for me, does it brake well at all?

maybe your booster is doin funny things?

[Gunner]

from memory thats a symptom of a stuffed booster, dont quote me on it but thats what they tell ya at tafe. pull the booster line of and check what happens, i think thats the diag for it

[Dongaz]

I think it might be the master cylinder as mine was shot when I got the 86 and my brakes were really crap...didnt help that the rear drum shoes didnt have enough contact either...good for some nice peg leggers :P haha

[jase ek]

i thnk its the mc or booster
im prob gonna change to r32 no abs booster n mc
wat will i need to do to the lines to use the r32, extend, bend, shorten the lines ??

[JDMJNKY]

i have sr20 brakes with standard everything else t series rear, has been fine pedal is a minute bit spongy but nothing at all serious!!! still stops fine

[kaibeecee]

keep in mind - the MC upgrade is a waste of time if your booster is dead.

R32/s13/s14 (onboard proportioning) and SV21 camry MC's fit & all have a 5/16 (1") bore.

buy brake line (hose shop/enzed carry it, listed as "bundy tube" - $7 a meter)

CA brakes are usually fine under 86 masters, get it reconditioned if need be.

[dustyae86]

there is two different size ae86 masters too

[Hen is a total nutcase]

Make sure your calipers are on the correct sides. The bleeder nipple must be at the top of the caliper piston.

If it's upside down it will bleed up ok, but still stay spongy.

Hen

[Dongaz]

how on earth could u get your calipers on the wrong way round?? :hammer:

[Jonny Rochester]

I only know about one size of master cylinder. 13/16" on both AE86 and KE70 and TE72. What is the other size?

When you make brackets for your brakes, you can choose to put them where ever you want. This is why they maybe around the wrong way. The bleed nipple being at the top is the only issue, otherwise it wouldn't matter.

[dustyae86]

<div class='quotetop'>QUOTE (Jonny Rochester @ Dec 9 2007, 09:29 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=449386)</div>
I only know about one size of master cylinder. 13/16" on both AE86 and KE70 and TE72. What is the other size?

When you make brackets for your brakes, you can choose to put them where ever you want. This is why they maybe around the wrong way. The bleed nipple being at the top is the only issue, otherwise it wouldn't matter.[/b]


there is a 15/16 master too, so you don't have to change your master when going to SR brakes sometimes, i think majority of them are 13/16" i think though

[Johnny_K]

Bleed them again but get a yourself a 600ml bottle, fill it half way or so with brake fluid, get sum rubber line (that can fit your caliper nipples) and make sure that the end stays at the bottom inside the fluid. when it comes to bleeding the brakes, undo the nipple, tell a friend to pump the pedal until you see all the bubbles have gone, then tell your mate to hold the pedal down, close the nipple, do that to all 4 corners and keep an eye on your reservoir as well. If this trick doesnt work then you got something wrong going on

[Hen is a total nutcase]

I know of 3 people who have swapped left and right calipers accidentally. Everything works, just you can't bleed them due to nipple being at the bottom. The pedal stays spongy no matter what.

Hen