I have a brake problem and I hope someone can help.

I have a 2007 Monte Carlo SS and it has been pulling the the left when braking. I replaced both front brake hoses and and had no problem bleeding the brakes and had a firm petal and took it out for a test drive but it was still pulling to the left. I then replaced the both front calipers but when I go to bleed the brakes I get no petal when even though fluid is coming out the bleeder valves in the calipers. Also, normally after bleeding a couple of times the fluid starts to come out with more force but it didn't when bleeding this time.

So I when ahead and bled all four calipers starting at the RR, LR, RF and LF. Brake fluid is coming out of all the calipers but the petal still goes straight to the floor and there really is no pressure when the fluid comes out. I don't see any leaks anywhere.

I tested the master cylinder by putting plug bolts the outlets and the petal was firm when I did that so it appears the master cylinder is good.

The only think I can think of is the ABS pump is not working. Does anyone else have any thoughts?

 

At the moment, when you attempt to bleed the brakes, very little fluid comes out and what does come out does not appear to have much pressure?
I am assuming nothing, so here is what I would check:
1. - Since you replaced the calipers, make sure the bleed screws are pointing up and not down (if they point down, you have the caliper on the wrong side of the car, you will never get a good bleed).
2. - When bleeding the brakes, I like to use a clear tube on the bleed screw that dumps into a bottle (lets you see if you have air and how much fluid comes out).
3. - When bleeding, have someone pushing the brake. I like to have them pump three times, hold the brake down, someone else open the bleed screw, once the air/fluid comes out, close the bleed screw. The person pressing the brake should NEVER release the pedal while the bleed screw is open (if they do, it sucks air right back in). Repeat step 3 until no more air appears to come from the bleed screw. Repeat step 3 for each wheel.

I hope this helps.

 

All bleeding screws are pointing up.

I use a rag when loosening the bleed screws so I can see how much fluid is coming out and if there is any air (which I don't see any air).

I get most of the air out with pneumatic air bleeder then I have someone pumping the brakes and holds the petal until I close the bleed screw.

I have been working on my brakes for over 35 years and have never run into this problem before.

 

So you have replaced both front brake lines and no pedal problem it just still pulled to the left. Sounds like the caliper piston was hanging up, and you add new calipers L /R front and now no pedal. So If the connections are not tight there would be fluid leaking past them and air getting in there. No tell tale fluid leaks at new caliper pistons either I would assume. So now the master cylinder has been plugged and pressure applied and you have a firm pedal. So to me there is either a fair amount of trapped air (unlikely, but possible) or one or both of the replacement calipers may have issues. If you put the old ones back on and you get pedal, that would be a way to trouble shoot things. 35 years doing brakes, you are no novice for sure. The only new thing is the lines (no problem) then the new calipers, now a problem.

 

Sounds like my first thoughts are no-goes. Bummer!
I have seen where the inside of a rubber flex line was restricted and required that to be replaced.

You certainly have a weird issue. I hope you have found the cause or find it soon!

 

I wanted to give an update to my brake problem.

Even though I tested my master cylinder and it appeared to be working properly I went ahead and replaced the master cylinder. I was able to get a good pedal with the engine off but the pedal still went to the floor with the engine on. I tried bleeding it with the engine on but no still no pedal.

I had picked up a used abs unit online for $70 so I replaced the unit. We bled the brakes with the engine off and got a firm pedal and while bleeding the brakes I could hear what I think was the ABS pump cycling.

Once again with the engine on the petal went to the floor. So I bled the brake with the engine on and was able to get all of the air out of the lines and now I have a firm brake pedal with the engine on.

I haven't tested the motor on the old unit but I am assuming something was wrong with it or with the module. I was able to bleed the abs system without having to take it to the dealer as I have no abs lights on and everything appears to be working properly.

I hope this helps someone in the future because this process really frustrated me.

 

I want to summarize what I believe I read, so correct me if I am wrong.
It did not actually let you bleed all the air from the system unless you bled the brakes with the engine running?
If that is the case, then that must be a newer GM /car thing (I admittedly have yet to do line bleeding on anything newer than a 2005). Perhaps the modern ABS systems require the ABS pump/module to be on and active and older systems did not.

Interesting and thanks for sharing that information! Something for me to keep in the back of my mind for future use!

 

Yes, that is correct. I did not get all of the air out of the system until I started the engine so brake booster could increase the pressure. Then I bled all of the wheels again.

I used clear plastic hose when I bled the brakes and was able to see air come out when bleeding with the engine on.

 

Who would have thunk... Nice home work there detective, even after 35 years of doing brakes too I earned something. What a pickle you were in, wow talk about consecutive component failures, what are the odds. Good job resolving this.