Changes made:
New Goodrich SS lines
New front left Proline caliper from Rovers North
Used master cylinder for testing,
Bench bled the master cylinder on the Rover using clear hose back to the reservoir from the hard lines, until there was no air, then reinsterted in the into the ABS modulator

Well I've done 2-3 previous brake jobs on this Rover and other cars and never had this issue. After doing a manual bleed(Brake pedal) per the RAV instructions, power bleed and modulator bleed using a Foxwell tool. The pedal is still soft and dives 3 inches of travel. I can pump it up with 2-3 pumps and lock up the front tires. Its definitely not safe to stop.There are no leaks on any of the calipers, no leaks from the modulator and or master cylinder. There is vacuum from the booster. I'm leaning towards a bad master cylinder. But odd how the master could be fine 4 days ago and now dead. Has anyone broke the master cylinder pushing the pedal too far past its normal travel? I keep a 2x4 under the pedal when bleeding. Any help is appreciated, I'm stumped

 

Does sound a bit like the cylinder is shot, air would be mushy all the time in my experience.

You could troubleshoot by blocking off various components and dead ending the lines to say a particular caliper or even all of the lines right out of the cylinder. See if perhaps ruling something out helps. I don't know the special Rover way to bleed brakes but on every other vehicle with very few exceptions, bleed in order of the wheels distance from the master cylinder and you're set. On very rare occasion I've seen poor designs result in a bubble that wouldn't push out, in those few cases I gravity bled or removed components to force the air out by benching them.

Can you dead end the system with hardware before it goes to the brake lines? If you still have the issue..... you'd know the problem at that point.

 

Right that was my next thought other than taking it to Goodyear in the morning and seeing what they diagnose.. I'd need to get male fittings and bypass the ABS modulator and go directly from the master to the hard lines for each wheel. I'm fine with spending more time on it. but I'd rather not buy another master cylinder if that is not the bad part. I'm just about certain there is not air in the system. I'm at about 5 quarts of fluid flush and I've not see a bubble since 4 quarts ago. I start with fluid in the container per the RAVE manual instructions following RHF, LHF, RHR. LHR for the manual bleed. The power bleed follows a different wheel pattern for the channels of the ABS modulator. Using the ABS modulator is they way to go for the power bleed.

 

I'm no expert on this topic but there have been a lot of recent threads regarding the rod going into the MC being misaligned leading to similar issues... Might be something to check.

 

Was the "new" master cylinder a used one? That's what l'm getting from your post. If so, it could certainly be the problem (even a new one for that matter, it happens). Why did you remove the original master cylinder?

Also, you replaced left front caliper...did you order, receive a left front caliper...because if you received/ordered a right front caliper by mistake...l think l know what the problem is...lol.

 

Here is a picture of the installed front caliper. Bleed screw is facing up so it is a LHF. I read the posts about someone installing 2 rears on opposite sides.
I could have 2 bad master cylinders. I'm going to try one more from a Pick and pull. If that turns out to be the fix, then I will buy a new one.

 

A new aftermarket MC is like 60.00. Most units from a salvage yard are 25.00 and will require new seals at the reservoir.

 

Today I installed a new master cylinder from Autozone. Looks exactly like the Cardone, Comes with a lifetime warranty. I bench bled it on the Rover per the instructions. Confirmed there is a hard pedal with solid plugs in the master. Then proceeded with a manual 4 wheel bleed per the RAVE. Then test drove it, pedal still dives to the floor and takes 2 deep pumps to be able to stop. I wouldn't drive it anywhere but around the block for testing. Then came back and did the ABS power bleed then a modulator bleed. I did see air come out during both ABS bleeds. Test drove again with no noticeable change. I'm totally stumped. Could a seal or valve be bad on the ABS modulator and allow brake fluid to pass through when it should usually be sealed off. That is the only component left. It was working normally a few days ago.

About 2.5 quarts of new fluid has been run through the system, in this attempt.

 

Any ideas, guys, I'm relegated to Goodyear in the morning to sort these brake issues and swallowing my pride. Its fine, but I have always figured out these odd issued in the past. Its a 2 pump chump and then I can really stop, just not safe to really drive.

 

Sounds like air in the system. Bleed the abs with wire or scanner. Pedal to the floor means your not pushing any fluid or pushing air