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Bmw e65 2004 730d


jimmy879
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Hello everyone i recently replaced all the brake pads and bled out the old oil on my 2004 730d and now i have a spongey pedel that sinks in to the floor. does anyone know what it could be?

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Morning James

Welcome to the Forum

Looking at BMW WIS the ABS unit should be activated as part of the brake  bleeding process a Good BMW friendly Diagnostic program should allow this.

Check the vacuum line to the servo and non return valve at the servo if they are perished it gives a spongy pedal. When you were bleeding the brakes are you sure you got all the air out of the system ? If you are re-doing it don't use fluid from an open can that has been sitting in the garage it doesn't take long to absorb moisture from the air (another spongy cause)

Good Luck

Dave

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i will try your suggestions and get back to you tomorrow. when bleeding the brakes i had car switched off and had a second person push th pedal while i loosened the nipple. i then put a pressure bottle on top of the resivwar and set pressure for 20psi and still no air came out. also tried sucking the air out from bottom but no use. non of these methods worked 

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Morning James 

OK process I follow is 

 Tools. Pressure Bleed kit 3litre (mine is around 15/20 tears old) Large syringe to suck old fluid from reservoir, Nylon mallet, Brake nipple spanners, Fluid (correct for car) Tip never store opened Brake Fluid it will absorb moisture from the air giving more problems long term

Jack up the car on level ground and place on axel stands, remove the wheels. Clean around all 4 bleed nipples and the Master Cylinder cap.

Set up the pressure bleed kit, I use a large syringe to empty the master cylinder, top up with fresh fluid. Attach the pressure bleed cap and apply 15psi

Always start at the wheel cylinder furthest from the master cylinder normally passenger rear. Check the catch bottle is attached and crack open the bleed nipple keep an eye on the fluid tap the brake caliper in case there is any air in the cylinders you will often see bubbles. When the fluid is clear and bubble free lock off the nipple and remove the catch tank. Check the Master Cylinder for level and move to the Drivers rear and repeat the process (I activate the ABS in case there are any air bubbles in there) Same procedure once the fluid is clear and bubble free lock off the nipple and move to passenger front Bleed and check Master cylinder level then the last Drivers front. Once complete check the master cylinder is at the full mark ( I keep a towel tucked under the master cylinder just in case there is any spillage) replace the master cylinder cap and sensor plug activate the ABS one last time. Job done

If the brakes are spongy or the pedal settles under pressure it is normally a leak or air is still in the system. Sinking Brake pedal under pressure (engine running) is in my experience often a Vacuum leak replacing the vacuum line and non return valve normally fixes it. Other causes can be Master cylinder seals worn.

Not trying to teach Granny here just passing on what I would do 

Good Luck

Dave

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ok so first thing i done was checked the non return valve by blowing into bothe ends as expected one end let air through and the other didnt. then i bled the brakes with the computer by activeating the abs pump  and again there was no air in the system. i ran a pressure test on the vaccum line and got 10psi and im also getting 100bar on the brake pressure 

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Morning James

That all seems good so if your still getting a spongy pedal it seems like master cylinder seals are about all that is left, No ballooning/swelling of flexible brake lines

Running out of ideas now

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Ok so just to be sure il start from the beginning, So up until i changed my brake pads all around, brake pedel were perfect.

I changed my pads and couldnt get a pedal. i bled them 5or 6 times atleast and still couldnt get a pedel. i used the computer to activate the abs pump and still no air came out. i pulled the non return valve off the vaccum line and it worked as it should and the vaccum line is putting up 10psi. yesterday i thought to myself what if its a faulty caliper so i squeezed the rubber hose on the front two calipers and it made the pedel slightly better but still not 100% so i tried the back two and same results

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From the description you have just given it could be a calliper or hose issue. If you pump the pedal do you get pressure that then fades ? 

Maybe calliper pistons were pushed back to far and are sticking ? Could be time for a calliper rebuild

Dave

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ok dave im back again i checked the master cylinder by blocking the feed lines at the abs, then tried the pedal and it was solid so it cannot be the master cylinder. i notice when i brake that front right caliper makes a creaking noise which i never noticed before so il try it next

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