Brake issue

[ogdawg]

I just replaced my master cylinder and booster with parts from a 97 Cherokee. I have been bleeding the brakes and am still have some issues. The brakes work with the vacuum line to the booster disconnected, I can stop the truck when rolling. when the vacuum line is connected the pedal goes straight to the floor. Doies this mean that there is still air in the lines or do I have another problem?

[Pete M]

I have a very similar issue in my 88 (original booster) after installing a new rear axle with disk brakes. I still haven't figured it out and it's one of the big reasons why the truck sits. :fs1:

[Andy in Pa]

I would say it probably means you need to bench-bleed your master cylinder. You have air trapped somewhere, unless a fitting is loose, but you would see fluid leaking out if that was the case.

[Automan2164]

:agree:

 

Try a bench bleed. Probably got some air in the master.

 

Rob L.