Spongy brake pedal after changing pads and disks
 

I changed my front brake disks and pads on my 2012 V70 D3 yesterday and subsequently found that I have a spongy brake pedal. When I start the car I find that the pedal can go straight to the floor but if I pump it a couple of times it is ok. However it will then loose pressure shortly after. When fitting the brakes I did not bleed them as the pistons were able to move back easily and the you tube links I watched did not show that this was required. I changed the rear pads and disks a couple of weeks ago and I did not experience this problem. Any help is greatly appreciated.

Try bleeding the fronts.

It is always worth pumping out the fluid in the pistons at each pad change as it works hard and can deteriorate over time and certainly doesn't help pushing it back into the master cylinder, and it may cure the problem.

That definitely sounds like air in the system and will need a thorough bleed front and back. You may have to go around it a couple of times to get a good pedal. Expect to use about a liter of fluid this will give the system a good flush. If it's still the same after bleeding then you may have damaged a seal in the master cylinder when you pushed the pistons back. You should have clamped the flexible hoses and released the bleed nipples before pushing the pistons back . This releases the pressure and any contaminated fluid in the wheel cylinders is expelled. Hope it goes well.

OP, if you use youtube as a definitive guide to brake pad changing and you do nothing with fluid changing and bleeding, you shouldn't be working on a braking system.

How did you retract the caliper pistons into the caliper? If you just pushed them back into the caliper, it has been known for the fluid pushed back into the master cylinder to "flip" the rubbers in the bore. When pushing the cylinders into the caliper ALWAYS open the bleed nipple. This will protect the master cylinder.

Salut!

Pookie

Work at a garage and see this lots, poor brakes after driveway fixers been at the brakes.

Had a car in last week for an MOT retest and the front pads were only touching two thirds of the disc, they fitted incorrect smaller discs.

As said has been known to take out the brake master cylinder, get the car to a garage if the brakes do not feel right.

Ps. not say the op is as bad as the example above.

Hi Pookie,

I've just had new front discs and pads (Borg & Beck) fitted to my 12 plate V70 D5 auto by my local independent dealer. I've now got a very similar situation where the brake pedal feels much spongier than before. I took the car back the next day suspecting that somehow air had gotten into the system, the same guy bled the brakes and showed me there was no air in there? He seemed to think all was OK and that braking efficiency would improve with time?

I was advised these discs come with a coating that takes a while to wear off but I've now done 500 miles and while the brakes seem a little better they are far from what they were... The car brakes OK but you have to use much more pedal pressure than before. Also when I pump the brakes with the engine running the pedal goes hard but then gradually pushes down towards the floor. With the engine off the brake pedal goes rock solid and stays that way - again the mechanic reckons that is normal for an auto and shows the brake servo is working OK but I've never noticed it before (although probably never had the need to pump the brakes before!) Is this normal?

I have spoken to two mechanics about opening the bleed nipples when you push the pistons back in and neither of them had ever heard of doing this? Likewise when I mentioned the rubbers may have 'flipped' if the pads are pushed back without opening the nipples they reckoned they had never heard of this either!

Assuming the rubbers in the master cylinder have reversed,. is there any way this can be fixed or is it a new master cylinder jobbie?

Look forward to hearing back from you or others - thanks!

I have heard about this rubbers flipping when you push the piston back thing, not convinced myself unless the master cylinder has a tapered bore.
The fluid pushing back into the master cylinder is the same as the master cylinder pushing the fluid out.

I confess I have never had cause to strip a Volvo master cylinder, all the ones I have, come with one or two seals on the piston dependant upon single or twin circuit, neither of which have room to flip when fitted to the cylinder, if they did have they would certainly flip when brakeing.

A spongy pedal can be caused by the new pads not being bedded in, long travel can be caused by the disk not being fitted square. Did you grease/ copper slip the mateing surfaces of the disk and hub? If so this may be the cause of your problems as it can cause the disk to be mounted out of square and give pad knock back, you then have to make up this extra clearance every time you brake giving you long peddle travel. Disks should be fitted to the hub dry, it is OK to grease the mounting spigot on the hub lightly to prevent the wheel sticking.

Quick test of a servo is to pump the peddle with engine off until it goes hard, start engine and peddle should move towards the floor as vaccuum biulds. It's a test I perform regularly on my vehicles, a longer time to build vaccuum than usual indicates a failing vaccuum pump or some other issue that needs investigation.
I change my brake fluid every 2 years so should have no moisture ingress problems but old fluid that has absorbed moisture can also give a spongy peddle.

It looks as if it's something you've done or the parts you've fitted that has caused the problem as it was fine previously. If you greased the hub/disk mating surfaces I would be stripping them and washing the grease off with brake / clutch cleaner or petrol, if not I would be stripping them and checking carefully every component as I rebuilt it.

If it comes to stripping the master cylinder then I would be looking for a service pack of new seals rather than a new cylinder if possible, it's a Volvo, they want £85 for a disc, eyes will water at the price of a master cylinder.

I most certainly would not be handing it over to a garage at this point, if you can find where you went wrong you will never make the mistake again, have someone else fix it and you will never learn.

Paul.

Does the brake caliper carrier move freely on its sliders ? This allows the caliper to align with the pad and disc .If it stiff or stuck this can cause the problem you describe as it springs the caliper and piston back after the pedal is released causing the excessive pedal travel to take up the slack. Haveing the car cleaned by so called " hand car washes" that use pressure washer can cause the problem . Check all parts are clean ,lubricated and move freely . Any run out of disc or wheel bearing play can also cause this problem. Some pads can take what seems like an age to bed in so if all is well and your sure there's no air in system ( bleed all of the system not just the front this may take two or three circuits of the car ) then give pads time to bed and braking should improve.

John Child, did you manage to get your brakes sorted? If so what was the problem?