Spongey brakes after disc and pad change

[Bobton125]

Evening all,
I replaced the discs and pads on my 2007 e93 bmw 3 series today. Whilst compressing the 2nd caliper piston with a G clamp I noticed brake fluid leaking out of the cap of the fluid reservoir which I had kept closed.

After finishing the job, I pumped t he brakes a few times and noticed the fluid level hadn’t dropped and was still over the max line so I used a small syringe and removed 10 or 20ml.

Now when I take it for a drive for the first time, the brakes feel very soft and spongey. Could this be anything to do with the overfull reservoir or could the discs and pads just need some bedding in and it’ll feel a firmer pedal over time?

Thanks

[E-bmw]

So, I am guessing that your pads were well worn & your fluid level was high when you did this.

The volume of displacement of the pistons filled with fluid has to go somewhere, and as you have found in the above circumstances it comes out of the top.

Make sure you have got it all off any paint work as it can easily eat paint if left on.

Did you sit in the car afterwards with the engine running & pump the pedal several times to re-extend the pistons to close up the gaps between piston/pad/caliper before taking it out?

[Andy 308GTB]

E-bmw said:

Did you sit in the car afterwards with the engine running & pump the pedal several times to re-extend the pistons to close up the gaps between piston/pad/caliper before taking it out?

This is a top tip. I always forget to do this and crap myself at the top of the road, every time. Every bloody time

[Bobton125]

E-bmw said:

So, I am guessing that your pads were well worn & your fluid level was high when you did this.

The volume of displacement of the pistons filled with fluid has to go somewhere, and as you have found in the above circumstances it comes out of the top.

Make sure you have got it all off any paint work as it can easily eat paint if left on.

Did you sit in the car afterwards with the engine running & pump the pedal several times to re-extend the pistons to close up the gaps between piston/pad/caliper before taking it out?

the old pads were worn to the sensor, so had about 1-2mm of compound still on the pad.

no fluid got on the paintwork

i pumped the pedal with the car off and then with it running but it still has the same soft feel to it when driving

[HealeyV8]

How good are the replacement pads? Some times it is the quality of the pads that gives different feeling at the pedal.

[steveo3002]

new pads will feel wooden /poor until bedded in ...if the pedal is soft then bleed them

[RobXjcoupe]

New discs have a coating of oil and should be thoroughly cleaned before fitting, also the new pads will need bedding in. You will notice the lack of contact on the disc for the first few miles.
Post some pictures if you can

[Penelope Stopit]

As mentioned somewhere above

Spongy = Bleed brakes

Somethings gone wrong and air is in the system

[NotBenny]

It's going back some time now, but I remember someone doing the same when I was a tyre fitter and the master cylinder needed pressure bleeding to correct the issue.

[stevieturbo]

As you have not tampered with the hydraulic system at all, there is no reason at all they should need bled.

It wouldnt be unusual for new setup to be a little spongey, but you arent elaborating as to how bad it really is. Is it a little, is it a lot ?

If it is bedding in, it should clear up with a few miles of actual use of the brakes. ( which doesnt mean driving 5 miles without using the brakes )

[227bhp]

Did you put the pads in the right way round?

[The Wookie]

227bhp said:

Did you put the pads in the right way round?

We had a client technician complain about poor pedal feel and stopping power with a new set of discs and pads a few years back.

They send the set back on an RMA and they turned up with heavily scuffed back plates and nice deep rings in the friction material of all four pads from the pistons.

I’m not sure what was more impressive, the fact that a professional technician and made such a colossal cock up, or the fact that he’d made said cock up then actually taken them back off the truck, put them all back in the box they came in and sent them back to us without noticing

I struggled to make the diagnostic report not sound sarcastic...

That said I think the OP would have a hard job cocking it up on an E92, from my recollection the body side pad has got a spring clip on it which slots into the piston and I doubt you’d get the cover side in the wrong way around without noticing it

I’d give it a few miles to bed in OP, failing that give it a bleed but nothing you’ve done should have risked introducing air

[Bobton125]

HealeyV8 said:

How good are the replacement pads? Some times it is the quality of the pads that gives different feeling at the pedal.

pagid pads and discs, OE spec i assume? don't think the 320i's used brembo?

[Bobton125]

stevieturbo said:

As you have not tampered with the hydraulic system at all, there is no reason at all they should need bled.

It wouldnt be unusual for new setup to be a little spongey, but you arent elaborating as to how bad it really is. Is it a little, is it a lot ?

If it is bedding in, it should clear up with a few miles of actual use of the brakes. ( which doesnt mean driving 5 miles without using the brakes )

this was my thinking? Being told it needs bleeding has confused me as i'm not sure how air could have gotten in there if i havent opened the fluid system anywhere except the cap


Hard to explain how soft.. it's not impossible to use, i can still stop the car, just not as sharp as it was before and the pedal isnt as firm

[Bobton125]

227bhp said:

Did you put the pads in the right way round?

haha yes i'm sure

[Penelope Stopit]

When you apply pressure to the brake pedal does the pedal feel similar to compressing a shock absorber?

[Bobton125]

Just to update,

After a few days of driving the car now feels back to normal. Panic over, turns out they were just bedding in..

Thanks for all of your replies