Soft brake pedal on evo3

[Chonga]

Hey guys, recently bought DIESTI's evo3. Will start a built thread on it soon, tho wont be doing much to it at the moment.

The problem is when i step on the brake pedal while im cruising i have to pump it a few times before it becomes firm.

Was told this is normal with evo1-3 running big cams.

Would a later model evo brake master cylinder help?

Cheers, Steve.

 

[4piknup]

when you cruising, you should have heaps of vacuum assist as the engine is in vacuum a lot. maybe needs a good bleed.
saying that it needs pumping up to get a pedal, leads me to think of bleeding brakes, or warped rotors, but you will feel them in the pedal.
also maybe leaking at the 1way valve on the booster

 

[DIESTI]

George should know this one but im sure it needs a Air chamber for the brake booster as its running big cams. George is there a DIY somewhere??

 

[Hypo]

I have cams and have no issues with my brakes.

Try bleeding the brakes and if that fails you may have a faulty master cylinder.

 

[Gianni]

+1 for bleeding the brakes. Maybe one of your bleeders is a little loose. If that fails then look into the cam thing.

Just out of curiousity, when brakes are stiff from pumping, if you push down hard on them do they end up slowly sinking and becoming floppy again?

 

[4piknup]

Just out of curiousity, when brakes are stiff from pumping, if you push down hard on them do they end up slowly sinking and becoming floppy again?

if they push through like that gianni, but not losing any fluid, it is bypassing internally on the master cylinder between the front and rear curcuits and needs a rebuild.

there are vacuum pumps available, they on most diesels. one guy in the states talks about a 12v compressor with the intake plumbed into booster, sort of in reverse.
also available are auxillary vacuum tanks, these were popular from when caravans had vacuum assist powered brakes. (early 80s?)

i dont think you should need it, i think your issues are elsewhere, ie bleeding. every time you pump the pedal, you are reducing the vacuum assist by emptying the vacuum booster and the pedal should get harder and higher, but the braker will become wooden and require more foot pressure to maintain braking ability.
all a booster does simply is for the engine to help you put the brakes on by sucking the pedal down.

 

[htgsr]

Id try changing the fluid and giving them a good bleed, im running kelford 272's an have no issues with brakes

 

[Gianni]

Reason I was asking if pedal slowly dropped was because once one bleeder wasn't done up enough and it would brake, but the harder I pushed the more floppy it would get and had to pump it, until one day it stopped. So I checked them all and one wasnt tight enough. From there I never had another issue (with brakes )

 

[4piknup]

Reason I was asking if pedal slowly dropped was because once one bleeder wasn't done up enough and it would brake, but the harder I pushed the more floppy it would get and had to pump it, until one day it stopped. So I checked them all and one wasnt tight enough. From there I never had another issue (with brakes )

but it would be a dead give away having brake fluid all over one wheel.
slightly off topic, i had a issue other day, i had front caliper off on 1 side and had pushed pads in a bit, when i put it back together i didnt pump pedal back up. now our driveway is a bit downhill... (oooh no, i hear you say) but the mrs car and the letterbox were fine. but when pressed brake pedal, i was suprised that there was so little pedal there. i think my back brakes are not working very well. must investigate.

 

[Chonga]

Hey guys, thanks for the replies.

Will take the car for a drive tomorrow and double check. But once the pedal is pumped up a couple times it brakes fine.

It just gets really annoying have to pump it every time before i brake hard.

Dont think there are leaks anywhere. So maybe will give it a bleed and see if that fixes the problem.

Cheers, Steve.

 

[khubner1]

my bet would be on warped rotors then but you'd feel that under braking atleast i do on the folks failcoon

 

[DOUGMO]

how does the pedal feel when the car is off?
hard as a rock or spongey?, if its spongey bleed the brakes in the correct order.
I have fitted a canister to a car with big cams to store vacuum but its not always required.

 

[Chonga]

When the car is off the brake pedal are exactly the same.

Spongy and after pumping it a few times it gets firm.

Dont seem to be leaks.

 

[ted]

If its spongy with the car switched of there will be air in the system so give them a bleed and see how they go, could be a leaking master cylinder. Slightly of topic ,you shouldnt have to pump your
brakes with warped rotors the most you will get is a shudder under foot or through the streering wheel with warped brakes. a VERY general rule of thumb is if the shudder
is in the pedal its rear, if the shudder is through the steering wheel its the fronts.

 

[EVOISM]

just coz the brakes r spongy or soft doesnt mean there has to b a leak.

u cant compress hydraulic fluid but can air, u may hav air in the lines.

bleed the brakes in the correct order, with some NEW fluid.

 

[bazeng]

Agreed, air in your system or your brake cylinder is stuffed. Stock brakes?

 

[Hypo]

For reference the bleed order I use

Rear Passenger
Rear Drivers
Front Passenger
Front Drivers

 

[bazeng]

Same,

I start from the furthest point of the brake cylinder to the closest.

 

[Velocity Racing]

yup what Baz said is the way to do it.

I also give the brake lines and the back of the calipers a light whack with a rubber mallet before bleading each corner, to ensure there are no air bubbles caught anywhere inside the cast part of the caliper.

Also worn wheel bearings will cause pad knock-off but that obviously doesnt explain the soft pedal with the car not being driven.

 

[SIVART]

its a long shot but check the brake line off the booster , as its got a one way valve in it and could be leaking , we change these abit on some of the new cars