I did the Expo rear end swap and of course the disk brakes.

Installed new calipers with flexible lines to new steel lines and a new "splitter" function and the flex line its attached to. Bled all brakes (a lot!) and as far as I can tell I have no leaks. But still have a mushy brake function that goes to the floor, when driven brakes are not good.

I did an in vehicle master cylinder purge, bleed of the outlet lines on the ABS unit, and bleed of the master cylinder (all according to procedure in the factory manual.) Didn't help, brakes remain as described above.

Been doing a search and some who have done the Expo swap and also some who did just did the rear disc brake conversion have experienced similar problems, but didn't see a solution or what the problem actually is.

Would like to hear from those who have installed rear discs to see what I'm missing here. Before I did the swap I researched and supposedly the existing master cylinder does not have to be changed (in fact the master cylinder in the Expo looked exactly like my Ranger master cylinder. )

Appreciate any and all input on this, I'm at my wits end trying to resolve this. TIA

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1998 4wd XLT 3.0 5 speed
8.8 4.10 LS axle with disk brakes/ 4.10 front diff
constant front halfshafts
31.5 x 15 Khumo tires
Odyssey start battery / 125 amp deep cycle batery
Dometic 1.3 cf refrigerator

I would try using a tool that can suck the brake fluid out of the line so that you know it is air free.

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2002 xlt 4x4 Hines ward edition

This. Or I believe the expo MC may actually be a little larger.

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2004 4.0 Ford Ranger XLT- Project Rustoration - coming soon.

Thx for the replies, but I found the culprit.

At someones suggestion, I clamped off the flexible lines at the calipers. Got good pedal after doing this. Pulled the wheels, calipers and rotors to inspect and found the inside "drum" area of one of the rotors coated with brake fluid. Only way that could have gotten there was by the piston leaking. Took both calipers back to Advance Auto got another set and installed. Bled the brakes and got pedal.

Leaking caliper piston right out of the box. Pretty frustrating.....

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1998 4wd XLT 3.0 5 speed
8.8 4.10 LS axle with disk brakes/ 4.10 front diff
constant front halfshafts
31.5 x 15 Khumo tires
Odyssey start battery / 125 amp deep cycle batery
Dometic 1.3 cf refrigerator