1999 GMC Sonoma Master Brake Cylinder Leak

[thepocketsavior]

Hello,
I'm having an issue with a leak between the master cylinder and the brake booster.
I replaced the master cylinder and now it leaks, the old one did not.
It only leaks when the brake pedal is depressed.
Is the some gasket or something that might have gone bad?

Thanks

 

[OnlySonoma]

There is most definitely a master cylinder to break booster gasket.
If it leaks from right between the 2 parts, then this is your problem.