Pumping brakes raises idle?

[mcfly94 169]

Hey guys for some reason when I pump my brakes my idle raises its XF with 250.

And how do you know if your booster is gone, my breaks squeal, creak and are sponging. 

[ILIED 316]

Change the fluid and see if they're still spongey.
My tip is to use a different colour to the fluid thats already in there. If its yellow in there, pick a blue one, so you know when you've got all the old fliud out.

As far as the idle, I'm thinking the NRV isn't working correct.

[mcfly94 169]

whats the nrv?

[SLO247 1,713]

Non return valve? The one that goes into the booster.

[revhead 1,392]

generally id say change the nrv if it doesnt stop the prob change the booster

 

when depressing brake pedal listen to the booster for hissing noises etc

[mcfly94 169]

generally id say change the nrv if it doesnt stop the prob change the booster

 

when depressing brake pedal listen to the booster for hissing noises etc

I can sort of hear noises coming from that area/

hard to change non return valve?

[revhead 1,392]

well id say the diaphragm in the booster is shot ,have you got another booster kicking around ,pretty easy job ,just undo master cylinder pull it forward un bolt booster ,should take 30 mins tops

[mcfly94 169]

may have to grab another booster and give that ago!, cheers guys!

[revhead 1,392]

3x bolts under dash 9/16 clip on brake pedal, 2x 9/16 bolts from master to booster that is all 

 

for the love of ford dont undo your brake lines ,not needed just pull it out of the way

[gerg 10,871]

whats the nrv?

Non-return valve I guess.

 

Spongy brakes could be a lot of things. Pads can delaminate and become a bit bouncy over time, fluid can get air/steam pockets in it, brake hoses can bulge under pressure, loose wheel bearings can cause pad/caliper knockoff, the list goes on.

 

Your idle rpm increases because your booster consumes vacuum from the engine, so it's the same thing as a vacuum leak. It should, if at all, increase only for a second. If it continues with your foot on the brake, your booster is faulty.

[mcfly94 169]

Found a spare nrv in the garage so ill give that ago.

 

My front brake hoses are cracking etc.. have new one to replace, so they could be bulging.

 

Don't think I have loose wheels bearings.

 

Pads could need changing, do need new rotors.

[Lord_fahrquhar 2,580]

In the booster there is a ceramic disc which the pushrod passes through to the booster.  If you hear a hiss its likely cracked and leaking air past the booster.  Only happens if you put a bit of force on it.

 

= increased air to engine  higher idle.

[mcfly94 169]

god damn brakes, hopefully get to the bottom of this soon, what are the chances of master cylinder gone?

[revhead 1,392]

if you pull it forward look at the back to see if its leaking fluid,other wise no its the booster

[mcfly94 169]

if you pull it forward look at the back to see if its leaking fluid,other wise no its the booster

forward out of the booster?

[revhead 1,392]

forward out of the booster?

correct towards the front of the car.

[mcfly94 169]

correct towards the front of the car.

alright thanks mate, will get another booster and check everything out, cross fingers!

[revhead 1,392]

youl be ok ,youl notice the rear of the master cylinder is clean its ok but if it looks a bit sugary white n crusty at the rear its shot or if its just plain pissing out fluid,

[mcfly94 169]

Slightly improved by changing nrv. Will grabbing another booster to see if can improve it anymore, but no noises atm.

I think my spongy breaks are definitely down to flexing brake lines and fluid.

[Crazy2287 1,886]

Change fluid before you worry about brake lines. Standard lines will still give pretty good pedal feel. But the tiniest bit of air in the system will send it up the duff.

[mcfly94 169]

Change fluid before you worry about brake lines. Standard lines will still give pretty good pedal feel. But the tiniest bit of air in the system will send it up the duff.

My front standard lines are cracking and brittle, and I already have the new ones in the shed , I used bendix dot 4 before, is that alright?

[Crazy2287 1,886]

I'm not sure. All dot 3's are compatible. I think some dot 4's are not. Look into that one mate. I'm using nulon super dot 3 but all those standard brake fluids are just brake fluids. Do not mix types. Thes the only thing with brake fluid really. Until you start getting into the exxy high temp stuff for hectic race applications.

Sure, if you already got the lines fit em!

[mcfly94 169]

Will do, wont wont hurt to run all new fluid through when I do the lines, and reseal the front calipers

[ZL. 19]

When i got my calipers reco'd the bloke told me to flush the brake lines with methylated spirit to get all the water out, but let it dry and evaporate off before you put in your new fluid, also as said dot 3 dont mix with dot 4. and silicon brakefluid is a waste of time( dot 5 ).

[ZL. 19]

because brake fluid is hygroscopic it absorbs water from the atmosphere, thats why its good to flush with metho.