xjaduhx

Was in the process of changing out brake pads when brake pressure was lost. Pads are on and rear pass caliper was replaced, now brake pedal is spongy and sinks to floor. Tried to bleed, but hardly any fluid came out. Pumped for 10-20mins, nothing out of 3 wheels except for a few drops from front pass side. Fluid in reservoir didn't move, brake lines are intact. Seems like a seal in master cyl is the issue, is this correct? Is there anything else that could cause this or I should be checking?

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LeX2K

See if fluid will gravity bleed, in other words fill the reservoir and open one bleeder at a time fluid should flow and drain slowly. If you have fluid moving from each bleeder but still can't get any pedal pressure your master cylinder may be bad. But try this before you replace, fill the reservoir (cover with a towel to prevent splash) and pump the brake pedal quickly to get out any potentially trapped air. At any point did the reservoir run dry?

HomerJay

Why did you change the rear caliper? If the spongy pedal and sinking to the floor started after the replacement, I think it's likely you're not bleeding the brake system correctly. There are few ways to do it with either one or two people, Google for more info. I would also recommend placing a small 2x4 or equivalent under the brake pedal to avoid pushing the brake pedal to the floor. This will prevent possible internal MC leaks.