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Spongy brake pedal - after changing all rotors/pads, rear calipers and bleeding system

29K views 19 replies 6 participants last post by  Voldsom Volvo 
#1 ·
So I changed all rotors and pads and also replaced the two rear calipers, followed by bleeding the system. But when testing the brakes, the pedal had become spongy.

When engine is off, it firms up after stepping repeatedly a few times. However, once the engine is on, the pedal is spongy and travels a lot.

The brakes do work and the handbrake also works on both rears.

When bleeding, I tightened the bleeder screw when the fluid was completely free of air. After the screw had been tightened the person stepping on the brake released the pedal - although not slowly - is this an issue?

Did I really break the Master Cylinder? I will try re-bleeding, but I am concerned that the MC crapped on me. Would the MC break if I turned on the engine when the MC was very low on fluid (as it had leaked from a broken caliper?

Help is much appreciated.
 
#2 ·
It sounds like you still have air in the lines.
If the MC ran low, you might of sucked in air.
 
#3 · (Edited)
Thanks, yes I'm hoping it still has air in it so re-bleeding hopefully fixes it.

But can I break a MC if I start the engine and let it run while the MC has too little fluid in it?

I started the engine as I forgot my key in the ignition and the battery low message came up - so I wanted to do a quick battery charge. Before and when the engine ran, the display showed a "low brake fluid" message and stop car immediately (but I guess that is just to warn you not to drive when brakes are no good - not a warning about potentially damaging MC?).
 
#6 ·
Well it showed low brake fluid before I changed the rear calipers, pads and rotors. But then I bled the brakes afterwards in the following sequence: Right Rear, Left Rear, Right Front, Left Front. But perhaps there is still air in the system.
 
#7 ·
Gravity Bleed the Clutch , If You have 1 .

Nothing like washing out the Lines ,just think of it as a Water Reduction Treatment : Let Gravity do the Work and buy's You the Time to get the Last one undone - It will be Time to Tighten up the First one .
This gives You time to get up and top off the MC .

( Electing the 2 Person Method or Low Pressure )
Never pump the Pedal all the way to the Floor , You should be tightening as the Pedal is on the way Down , and Certainly Not Bleeding 3-4 ft of Continuous _ Squirt Fluid . read ( Pressure Bleed )

I'm wondering If You got Air in the ABS system ? Thou
 
#9 · (Edited)
Thanks, but there are no spring retainers on the rear pads, nor do I see any place on the rear caliper where the retainers would be clipped on? I am using OEM calipers and OEM pads. According to the instructions which came with the rear pads, you position both pads on the bracket and then slide the caliper over them. All I see is a spring on top of the inner pad.

Just bled the system again and there is definitely a big improvement compared to yesterday. However, I am still not fully happy about the brake pedal travel. It is however more or less as before I changed the brakes.

I am curious as to how much travel there is on other members' S40/V50s? Also, is it possible in any way, to adjust how much travel there is (sort of like adjusting the parking brake)?
 
#12 · (Edited)
I agree, the brake "bite" isn't as sharp as a BMW (2-piston calipers up front?), but that's just the nature of our single-piston, sliding caliper design. I have another car with Brembos all around so I know exactly what you mean, those bite hard.
You could upgrade the fronts to the Wilwood kit, which will definitely improve the feel. Maybe upgrade the brake lines to steel braided ones?

As far as adjusting the initial brake travel...I'll leave it to someone else who has messed with the brake booster.

I do feel the brakes after pressing down an inch or so. But it definitely feels spongier than monoblock calipers.
 
#13 ·
The BMW is an old 323i (E36) which is slower than the T5 but the engine is still a gem which spins and purrs like only a BMW straight six does. But more importantly I much prefer the brake feel to that of my V50 and there is definitely less initial pedal travel.

As for the brake install and bleed method described, do you have any comments/criticism? It was my first time doing it, so I have been extra careful and meticulous, but you never know if you did something wrong or left something out.
 
#14 ·
As for the brake install and bleed method described, do you have any comments/criticism? It was my first time doing it, so I have been extra careful and meticulous, but you never know if you did something wrong or left something out.
As far as the bleed procedure, it sounds right. Did you constantly check the master cylinder to top it off after bleeding each caliper?
The pad install should be fine if you followed the enclosed instructions.
 
#19 ·
SS lines don't do a "better" job, but they are more rigid internally and therefore give you a firmer pedal feel. However, pedal feel is also affected by pad type, pad clearance, rotor flatness, caliper design, dirt, etc etc. So don't expect a miracle from lines alone.
 
#20 ·
Thanks. I will definitely consider SS lines.

I guess since I installed new OEM rotors and pads front and rear, cleaned and re-lubed calipers and brackets and bled the fluid, that the brake pedal feel would have improved. But so far, I feel no difference at all.

Do you know if it is possible to adjust/reduce the initial pedal travel somehow?
 
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