My 01 V70 had superb brakes although the booster started hissing. As the booster was hissing more and more, the brakes were totally fine. After I replaced the booster, and the master reservoir got tilted, I have bled the brakes three times and just started on my fourth. There is always new air there, and there are no breaks until the pedal is depressed a bit. This time when trying to bleed the brakes I'm not able to get the pedal firm even though I'm pumping and pumping on the brakes. (I've bled brakes before and succeeded.)

What's up, does anyone know? Do I need a new master sylinder? If so it got damaged when I replaced the booster, because everything was fine before. Can the sylinder get damaged when tilted?

BTW, it looks like there is some gooey stuff in the top of the reservoir. It might be old dust or small particles floating around. Would that have anything to do with it?

Can anyone help?

 

Did you disconnect any of the brake lines?

 

I didn't disconnect any brake lines. But I forgot and tilted the master sylinder, possibly also the ABS module (don't remember) when I worked the new booster in. Could air have gotten into the ABS module? If so, is there a bleed screw or something to get it out?

 

I just took it for a drive and when I got back we tried bleeding again on the same wheel. We were able to pump the pedal hard before cracking the bleed screw open, but after having opened it once (still with bubbles coming out), the pedal is not getting hard. It keeps sliding to the floor. That makes me think the main sylinder seal is bad. It wasn't this bad the last time I bled the car a few weeks ago. I'm guessing, since getting air into the system made us have to depress the pedal further down, the seal has been wearing on a part of the sylinder it hasn't worked over much before, and there was probably debris and stuff there wearing on the seal. But why does the pedal only go to the floor after having opened the screw once?

Anyway, there must be another issue too, something that either lets in or keeps the air in the system. Now there is very little pressure and it takes time to get all the fluid and bubbles out, but the first times I bled I had no problem getting it out, and I went through more than a quart of fluid, so I know all the old fluid was replaced. I think it did improve, but not by much, every time I bled it, and that makes me think there is no new air getting in. The only place I can imagine air hiding is the ABS module.

 

Safely take the car out and in a safe place try to activate the ABS and see if the brakes get better.

 

Thanks, Tech, I activated the ABS and that seemed to help. There was still air in the lines, though, and even after bleeding the brakes, it still feels like there is more air in there. Will it help further if I continue to activate the ABS a few more times?

I know the master sylinder has been damaged, because the pedal slowly goes to the floor when depressing it. But if there was no air in the system, the brakes should still grab right away. Am I right?

 

Activating the ABS might help.

If the brakes are normal the pedal will be touchy like it was before.

I would activate it a few more time then maybe one more bleed and see if that helps.

 

When I bleed my brakes, I use a clear hose from the bleeder nipple to the collection pan. When you bleed your brakes, are you seeing bubbles in the fluid as you bleed, or are you describing the feel of the brake peddle? If you are seeing bubbles, and as you have stated, you never "opened" the system, then I believe your master cylinder is failing and the source of the bubbles. If you are not seeing bubbles, then this problem is beyond my skill set.

Jerry