Brake problem

[Native]

Is it possible for the brake booster or master cylinder to go bad by sitting for a couple months? when I switched axles I changed calipers from a early jeep XJ to a later model jeep ZJ (both from a d30)now even after I've bled the brakes multiple times the brakes are still soft like there's a broken line but everything is intact so I think the booster or master cylinder is out. has anyone ran into this problem before if so some info as to what was the problem would be nice cause I need to have my jeep working again.

[ThrottleJunkie]

most of the time when a booster goes bad the pedal gets hard, if the new brake calipers that you put on are bigger then there is a chance your bore in your current master is not big enough.
I'm not to savy with xj or zj stuff but when I went to one tons under my yj I had to try three differnt masters until one finally gave me a good pedal. Started with a stock 15/16" bore then went to an expensive 1" bore of a tj, ended up with a chaep $20 1 1/8" bore of a van that kicks ass now.
I would start by bleeding the master then go to the wheel thats farthest away and bleed everything. If that doesn't work you may want to look into a differnt master.:Big Grin:
good luck with all that!

[Native]

how would I go about bleedin the MC I've never heard of doing that before?

[ThrottleJunkie]

When you install a new master you bench bleed them from the lines back to the resivoir in a vise. Then whe back on the vehicle crack the lines right at the master and pump pedal just like you whould at the bleeder.

[85runner]

Splurge on a vac bleeder and do it to it.

[GloNDark]

The problem with bleeding the master in the truck is the angle. Normally the sit angled towards the back of the truck, which makes it near impossible to get all the air out of the Master.

Bench bleeding works great, Vacuum bleeding is a way to go too if you have access to one. But i've seent people jack up the rear of the truck and set it really high on jackstands and "bench bleed" in the truck with decent results too. Sounds crazy, looked fucking crazy but i'll be damned it worked. hahaha