NEED HELP Brake pedal noise/No full pedal

[Hobbyist4Life]

Hello,

I have this weird brake pedal noise, and brakes apply firmly about halfway through (after the sound is gone) and I can't seem to figure it out.

This is a video of the problem:

Now let me give you a little bit of the brakes history on this car:

Spoiler

About 1.5~2 years ago I have completely ignored the brake noises (knowing I needed new front pads) to the point that the out pad on the passenger front wheel completely vanished and the piston and all the fluid came out. Pedal would directly sink to the floor as there is no brake fluid.

I drove it in that condition from college all they way home (about 25km) as the car would actually slow down when the pedal gets firmly pressed into the floor.

Needless to say, I got 2 new front rotors (Raybestos) and ACDelco pads, as well as a caliper from a scrap yard. The piston of that caliper was hard to compress (later found out that it was not releasing when the brakes are released) and turned out to be rusted.

I bled the brakes after installing everything using 2 person method (starting from passenger rear all the way through to the driver front) but the brake pedal felt exactly like in the video.

The brakes were a whole lot better before the incident, so I thought that I still had air in the system and decided to leave it for later... yeah, right.

It was left that way until about a month ago, I installed remanufactured passenger side caliper from Amazon (ACDelco 18FR1893) and 2 ACDelco professional rear rotors, as well as new front and rear pads.

I flushed the system while I was in there, hoping to get better brakes, and ended up with this video.

So far, I've tried:
- Bleeding the system
- Bleeding the ABS module using a scanner (Auto bleed function)

But to no avail. I think it's worth mentioning that while doing the auto bleed, the pedal wouldn't go all the way up, just about half way (where the brakes would start applying after the sound) and go back down. The engine was also on, not sure if that would make a difference.

Could the master cylinder have got damaged for running it dry for 25kms? Or is it something else giving me this issue?

I also pulled the fuse a couple of days ago as the ABS would sometimes kick in at low speed going to a stop. Both front wheel bearings were replcaced with Detroit Axle ones about a year ago, and the driver side sensor started having probles so I put the original one back on.


I would really appreciate any help I get.

Thanks in advance.

Regards,
Hobbyist4Life

 

[Mooseman]

Could very well be that the master cylinder has gone bad. The noise you hear is the rush of air from the vacuum booster. If you push hard and fast enough, most will do this but normally isn't so evident. Yours is going too low and fast before offering resistance.

Be sure to bench bleed the MC before installing it.

 

[Hobbyist4Life]

Could very well be that the master cylinder has gone bad. The noise you hear is the rush of air from the vacuum booster. If you push hard and fast enough, most will do this but normally isn't so evident. Yours is going too low and fast before offering resistance.

Be sure to bench bleed the MC before installing it.

Would bench bleeding the current MC result in any improvement?

Also, would an unbranded aftermarket MC from China be any good?

Finally, what should I do for the ABS problem that I'm having?

Thanks for the quick reply btw.

Regards,
Hobbyist4Life

 

[Mooseman]

It might. Can't hurt to try, especially since you said you ran it dry.

I'd be wary of CCC (Cheap Chinese Crap). It might be good but are you ready to roll the dice on such an important component?

For the ABS, it's likely a failing front wheel bearing hub. Those symptoms are indicative of that 90% of the time. I've also experienced that with new CCC hubs.

 

[Hobbyist4Life]

It might. Can't hurt to try, especially since you said you ran it dry.

I'd be wary of CCC (Cheap Chinese Crap). It might be good but are you ready to roll the dice on such an important component?

For the ABS, it's likely a failing front wheel bearing hub. Those symptoms are indicative of that 90% of the time. I've also experienced that with new CCC hubs.

I see what you mean, but are Detroit Axle hubs considered CCC? Could the problem be with the sensors that came with the hubs? I already put the original on one side, might as well replace the other side and see what happens.

As for the MC, could it still have air trapped in it, even after having no air coming out the bleed screw and auto bleeding the ABS?

Regards,
Hobbyist4Life

 

[Mooseman]

I've heard good things about Detroit Axle so they should be OK. Could be the sensor (which is the other 10%). How old are they?

The MC might have air trapped, which is why you bench bleed before installing a new one. Again, nothing to lose in trying.

 

[Hobbyist4Life]

I've heard good things about Detroit Axle so they should be OK. Could be the sensor (which is the other 10%). How old are they?

The MC might have air trapped, which is why you bench bleed before installing a new one. Again, nothing to lose in trying.

I installed them around March, 2017.


What can I use to bench bleed if I don't have the bleeding kit?

Regards,
Hobbyist4Life

 

[Mooseman]

Brake lines? If you buy a pre-made one, cut it in the middle, connect to the MC and bend back into the reservoir. Something like this:

 

[Hobbyist4Life]

Brake lines? If you buy a pre-made one, cut it in the middle, connect to the MC and bend back into the reservoir. Something like this:

Can I connect the lines as shown in the picture while keeping the MC in the car and use the brake pedal?

Are there any other options than brake lines? I do have the clear tube that I used to bleed the brakes.

Regards,
Hobbyist4Life

 

[freddyboy61]

For the ABS issue, check the mounting surface for the speed sensor. Sometimes rust and corrosion build up under the mount and causes the sensor voltage output to be less than ideal.

 

[Mooseman]

Can I connect the lines as shown in the picture while keeping the MC in the car and use the brake pedal?

Are there any other options than brake lines? I do have the clear tube that I used to bleed the brakes.

Regards,
Hobbyist4Life

I suppose you could do it in-vehicle. You would need to find fittings that can screw into the outlets of the MC. You have to get the end of the hose or line submerged in the reservoir to prevent sucking in back air.

 

[Wooluf1952]

I've done the "bench" bleed with the MC already mounted in the car. I used the tubes that came with the new/rebuilt MC. The biggest problem is making sure the tube ends stay submerged in the reservoir and pumping the brake pedal and watching for air bubbles. Having a helper does help.

 

[Hobbyist4Life]

Will see tomorrow if I can get my hands on some old brake line, or fittings, locally.


Regards,
Hobbyist4Life

 

[mrrsm]

Post # 18

https://gmtnation.com/forums/threads/is-brake-fluid-still-good-or-not.15902/