New to the forum. I have a 93 Civic and last week the brake pedal started going soft. Then, it went to the floor and stopping was scary. I have checked and there appears to be no loss of fluid in the master cylinder. I have checked all 4 wheels and no visible leaks? What could this be? Any ideas? Thanks in advance.

 

Soft brake pedal + no fluid loss/leak = bad master cylinder (generally)

You might try bleeding the hydraulic system of possible trapped air first, though I think a new master cylinder is your final destination.

 

Yes your master cylinder is worn out. Rest of the system should be OK. Check that brake fluid from the master cylinder didn't get into the brake booster, because that will cause the diaphragm in the booster to blow out in a few months.

 

Also it could be because someone put a substance other than brake fluid into the reservoir. The entire system is destroyed then.

 

rear brake pads being wore will also give you a soft pedal an make it gotto the floor, may want to check those as well

 

I had the same thing happen in my old 92. Master cylinder was worn out.

 

a blown seal inside of the master cylinder will not cause the system to lose fluid but will cause the pedal to go to the floor. you need a new master cylinder. i had the same exact problem.