Soft brakes on Toyota Sienna

The brakes on my 2007 Toyota Sienna suddenly went soft. The mechanic first replaced the rear pads, which needed to be done anyway, and when that didn’t fix the problem he replaced the master cylinder. The brakes are still very soft. He has bled the system several times to get rid of possible air in the line, but that hasn’t fixed the problem. Any suggestions?

I had the same problem on a vehicle I was working on and the fix was that the bleeder vavles were on the bottom of the calipers so I had to take them off and bleed them upside down, just make sure you hold the caliper on the rotor when I did it.

My 2004 Sienna had the same problem. My mechanic said it was probably a sticking slider on one of the calipers. I pulled the front brakes and the passenger side caliper had a completely frozen slider. I replaced the caliper and now the brakes are firm and just like brand new.

@SteveSienna did the mechanic bench bleed the master before installing it?

Did the mechanic bleed the brakes with a diaphragm brake bleeder and the appropriate adapter?

Was there any work done before the brakes went soft? Seems like someone has to check the bleeders and hoses/calipers all around.

If the bleeder valves are on the bottom of the calioer, you have the calipers on the wrong side of the car.