When driving I can push the brake and ok then next second pedal on floor, had rear brake pads changed at mot couple months back and not been tight since, fluid been replaced and still same any ideas
Thanks the problem came after pad replaced the garage checked no leaks so will get them to bleed system again see if fixes, I did think about piston issueYes.
The system may not have been bled for air completely, it is easy to stop bleeding too soon, before all the air is out.
Leaks. Has the fluid level dropped? That would indicate a leak.
You should return your car to the brake workshop, and get them to fix it. Look over Al the joints and potential leak paths, clean /dry them off, observe for further leakage.
When was the fluid replaced? During the pad replacement? Or afterwards as part of trouble shooting?
If the issue was not present prior to the pad replacement, then it would seem that they may not have done the job completely.
There is of course the possibility that the caliper piston now leaks after being retraced, this will not be the workshops fault, tho should have been noticed during a test drive.