Dual piston caliper swap problem - help?

[Flutterbyfilms]

I just swapped my front calipers for dual piston calipers off a 2000 Galant, and now my brakes don't work.

I thought at first there must be air in the line. We bled the master cylinder, then each wheel in the proper sequence, with speed bleeders, and got all the air out. Still doesn't work.

So, today we check all the parts to make sure everything is seated and on properly, all lines sealed tight, etc. Everything looks fine.

We decided to bleed it all again to make sure we got all the air out if that was the problem, so we did it again, starting with the master cylinder, and each wheel in sequence. No air out of any of them this time. Still brakes don't work.

I know we bled them correctly, I know everything is installed correctly. When the car is off, the first press of the brake is spongy, but it stiffens after that, leading me to believe there aren't any leaks in the lines or anything. When the car is on, however, the pedal goes to the floor. I can pump it fast and seem to pump up some pressure, but it goes flat again if pumped slowly, which leads me to believe that maybe I need a different master cylinder.

Has anyone who has done this swap had problems? I talked to a mechanic who said he thought that my master cylinder may not be able to provide enough pressure for the dual piston calipers, and I would need the one off the same car. Is this true? It makes sense.

Other than that, I can't think of anything that could be the problem. Keep in mind, my brakes worked before we did this swap. Any help would be appreciated.

[Flutterbyfilms]

Forgot to include that my car is V6 2001 GTZ.

The calipers are off 2000 I believe.

[kolio]

do you have abs? cars with abs require specific bleeding methods to purge air from the abs unit. there could still be air in the abs unit.

[Flutterbyfilms]

Yes, I do. I don't see anything in the Haynes manual about ABS. What do I do different?

[Flutterbyfilms]

Ok, so I need to bleed my abs valves. Where are these located on our cars?

[kolio]

somebody else needs to chime in since i have a 7th gen with no abs.

[silver01g]

have you try calling the dealership (mits motors)?

[pinoyesv6]

what sequence did u bleed the brakes in?

[Flutterbyfilms]

I bled master cylinder first, then

right rear
left front
left rear
right front

which is what the haynes manual said, but now looking up stuff about bleeding with abs,

I should have bled

master cylinder
rear abs valve
combination abs valve
front abs valve
then the same wheel sequence

I just don't know where these abs valves are on the car.

[spdracr]

I didnt even know that there's a sequence for bleeding the brakes in the first place

I guess I learned something new

[Flutterbyfilms]

Any help on where the abs valves are? I'm going to try to do this tomorrow morning.