Hi everyone, I recently did a rear axle swap on my 2006 chevy cobalt ls from an 2006 ss with the rear disc brakes and now I'm having an issue. The brakes are very squishy and you have to slam them almost to the floor to engage them. I replaced the master cylinder, bled the brakes twice and adjusted the rear and front calipers. My car doesn't have abs. I'm confused to as of what is going on, so any help would be greatly appreciated!


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So you yanked out the ABS, and changed the spindles/stub axles ? Or the whole torsion beam...

 

No, my car didn't come with abs. And I replaced the whole torsion beam with the one that has rear disc brakes. My car just as a proportioning valve like this.

 

You sure there isn't a prop valve and ABS? I thought ABS would be pretty commonplace by 2006
Wiki says they all came with ABS.
https://en.wikipedia.org/wiki/Chevro...lt_SS#Overview


My service info says
"This vehicle is equipped with the DBC7.4 Antilock Braking System."
and also
"Pressure balance control on ABS equipped vehicles, is achieved through dynamic rear proportioning (DRP)"

looks like the prop valve has a bleed screw too. Did you try that?

maybe the MC and other components need to be specific to disc brakes

Did you use DOT3? Fluid topped up?
Rotor at least 12mm thick?

If it uses a vacuum assist booster then I would check that next.

 

Well the SS Cobalts all came with abs, I have an LS. I've spoken to some other people and a majority of them said that there's probably air in the system that need to be bled out. I actually tested my brakes out earlier today and they felt better today than they did yesterday. And proportioning valves come with bleeder valves too?! I didn't know that

 

oh ok. vehicle is an LS. Rear end came from an SS. got it.

This sure looks like a bleeder :

but I could be wrong.

 

I would check but I'm afraid of getting more air in the system. And I think I need to bleed the master cylinder again and bleed the whole system again, but I is there a chance my proportioning valve has air trapped in it?

 

sure there's a chance. it happens.

If you apple pressure to the brake pedal then air can't get it. Just open it slowly.

 

Okay, just tested it and that was not a bleeder screw lol. But, I did find out the SS does use that proportioning valve so I think that the proportioning valve isn't the issue and I highly doubt the abs module matters

 

air does get trapped in ABS modules. That's why there are ABS bleeding procedures.

The PV has be bled manually. That means loosening off each port as you bleed it.