Brakes no fluid driver side caliper

Hello I have a 92 buick lesabre ABS about 6 months ago the anti-lock light came on, so my wife took it to a dealer close to where she works to check it out, the mechanic said it was modulator ? very expensive to replace. He said the brakes would work just fine she would just have the light on and no anti-lock brakes. Well that did work fine for 6 months she came home Thursday and said brakes were really bad. So I go out and the pedal had a hard spot at the top of petal and then it would almost fall to bottom before it would grab, So I check fluid its ok, I had her push the petal and i listened to brakes I could hear the rear ones engaging, I took it for a drive down the driveway and hit brakes and rear brakes slide so I know the front ones aren't working, So I go to bleed them and passenger side seems normal, I use my vacuum pump and didnt get any air, I go to drivers side and no fluid comes out when i open the bleeder, I put the vacuum on it and pump it up to 20 pds vacuum and i get fluid but not much ( nothing like passenger side) so I pump brake petal and the caliper doesnt work, could the distribution block have gone bad ? is there anyway to check it ? Any help is greatly appreciated.
Thanks Jerry

Replace the flex hose that goes from the bracket attached to the frame and the other end to the caliper.

Replace the flex hose that goes from the bracket attached to the frame and the other end to the caliper.

Ok I will do that tomorrow I will let you know thanks Jerry

I think KOK328 is right on the money.

If not the hose, possibly the master cylinder.

Well I changed the hose, I got fluid there but the caliper is still not working. I followed the line back to the distribution block and loosened the line, to make sure there was fluid there, but the oil started dripping as soon as i loosened the line.

I guess master cylinder tomorrow.

Thanks for your help, Jerry

Remove the offending caliper and try to compress it, to determine if the piston has seized up. Replace as necessary.

Hello I removed the caliper and the piston compressed ok, So I went to napa and got new master cyl, and its fine now. Thanks for all the help

Jerry