Spongy brakes despite recent bleeding

hu5ker555 · Post by **hu5ker555** » 24 Nov 2018, 19:03

2008 S60 2.5T, 185K

So after driving a rental vehicle (nearly new), and then driving my S60, I realized that my brakes are not nearly as tight as they could/should be. I changed the front pads (they weren't terribly worn and the rear ones looked ok). I then bled the system (one man version with bottle. I was very careful to not allow air back into the system and kept the master cylinder full. The brakes are still soft/spongy...very similar to how they were before I changed the pads and bled the system. When bleeding the system, I saw no air bubbles at all. Any suggestions on how to tighten up the braking system?

zjevik · Post by **zjevik** » 24 Nov 2018, 20:47

You could try to change brake calipers. My front caliper was sticky and while changing them I saw the piston was soo rusted that I could barely move it even with tools. I suspect that the braking response would get better if I change the back calipers as well.

XC70Rider · Post by **XC70Rider** » 24 Nov 2018, 21:47

Did the caliper pistons press in easily when you threw on new pads? If not then I agree with throwing on new calipers. If not much force was needed to press in the pistons then check out the vacuum pump and it's check valve switch. When I got my 2007 XC70 last May my brakes where spongy at startup due to the burnt vacuum pump and stuck open check valve switch. This thread helped me fix that issue:

viewtopic.php?f=9&t=43817&hilit=cold+brakes

hu5ker555 · Post by **hu5ker555** » 25 Nov 2018, 08:35

Hmm. Any chance is could have something to do with the ABS? I've seen where people use a scan tool to autobleed the ABS system.

zjevik · Post by **zjevik** » 25 Nov 2018, 10:11

Check the vacuum switch as XC70Rider suggested. You can set the ignition to position II (with engine not running) and every time you hit brakes you should hear sound and the brake pedal should not be hard.

You can activate the ABS pump in VIDA if you have it to bleed the system. But from what I read it's rare to have air in the pump unless you took the master cylinder off.

Post by **oragex** » 25 Nov 2018, 11:14

To properly bleed the calipers, a plastic tube must be keep over the nipple to prevent the air to get sucked back in. Also note that the vacuum bleeders are not good at bleeding the calipers (the pressure bleeders is the way to go) www.youtube.com/watch?v=4dM9nbMLyvE

Or maybe try bleeding the master cylinder and the ABS block www.youtube.com/watch?v=mGU-glkL2B0

Elekos · Post by **Elekos** » 25 Nov 2018, 12:30

Despite my car is old, mechanical problems are always actual- like this one. In my TWO repaired volvos I found two reasons of spongy brake pedal- first was
swelling flexible hoses near calipers - enough that just one swells from the pressure and the effect of spongy brakes guaranteed. To confirm this, you will need someone to help you depress the pedal and check for possible swelling at the same time.
The second reason I know is the worn cylinders or pistons in calipers, when the piston pushes unevenly against the brake pad (aslant) and therefore there is no flat pressure against the disc, and the piston hooks one side of the surface of the caliper cylinder.
The above cases belong to rare, but are confirmed.
However, the most common reason concerns intensively used brakes (eg cars with high mileage in the city) is the wear of the initial part of the brake master cylinder (brake pump). In the initial step of the piston movement pressure does not grow efficiently, but only later (at the end of the piston movement) pressure is fully increase . This testifies to the larger diameter (conicity) of the pump cylinder in the area most often used by the piston. Then, of course, it will be necessary to replace the complete master cylinder.

p.s.- forgive me my clumsy English

dj_v70 · Post by **dj_v70** » 25 Nov 2018, 15:55

Another reason for soft brakes are rusty stuck caliper guide pins.

Post by **oragex** » 25 Nov 2018, 15:57

Elekos wrote: ↑25 Nov 2018, 12:30 swelling flexible hoses near calipers - enough that just one swells from the pressure and the effect of spongy brakes guaranteed. To confirm this, you will need someone to help you depress the pedal and check for possible swelling at the same time.

This is a very good idea. My 2003 had both front flexibles cracked at the lower point at near 160000kms, so these must be replaced.
An important safety check on all these cars. I had another car in the past that was not checked for these and left me without brakes in the middle of the road. Plus, the 'safety' brake on the S60 (the parking brake) is all but powerful enough to stop this car.