I removed the master cylinder on my 2007 vw jetta 2.5l and installed a new one but noticed the was something wrong with the threads on the new one so installed the old one and I have no pressure in my brake unless the car is off if it is on the brake goes to the floor with no pressure unless it is pumped up can you help ?
Did you bench bleed the master cylinder?
Yes I have
Check to see if that car requires a special bleeding procedure. Other than that, that old master cylinder may be leaking internally.
Is there a way to test it to see if its leaking internally and where can I find this procedure ?
You might be able to find the bleeding procedure on a VW enthusiast site, other than that it would be in the manufacturer's service manual or Alldata. Alldata offers an inexpensive DIY service.
https://www.alldata.com/diy/en
I don't know if there's a way to determine if the master is leaking internally other than disassembly to check seals and bores. Could be an issue with the ABS as well. (These are just generic suggestions as I am not familiar with that car.)
Did you bleed the brakes?
I tried the rear right and only seen fluid come out I tried this 4 times to see if any air came out
I heard there is a sequence to bleed the brakes on this car does that matter ?