Brake booster

[grabeb]

Do I need to actually bleed brakes when swapping the booster?

I can't recall, been a while.

 

[macleanflood]

Yes and probably bench bleed the booster.

Pay attention to the proportioning valve.

Plenty of threads on this forum discussing this very topic. Some good suggestions below.

-Mac

 

[grabeb]

Yes and probably bench bleed the booster.

Pay attention to the proportioning valve.

Plenty of threads on this forum discussing this very topic. Some good suggestions below.

-Mac

I will do and trying to read up. Not my first brake job or booster replacement by any means, but not real often.

I guess I don't recall messing with the closed system of the brake hydraulics. Maybe I'll have to though.

A quick search below didn't show proportioning valve, guess I'll look more. I suppose it obviously needs and has one with disc's and drums. Again, I'm lost on why it would be messed with.

I'll go read more.

 

[macleanflood]

Proportioning valve has a shuttle valve that can move when all the brake fluid goes one way or another.

-Mac

 

[grabeb]

So daughter, who drives the jeep, met me and friend for morning coffee. She said her jeep wouldn't turn or something as she tried exiting the hwy this morning in rain. I figured she Hydro planed, but thought wierd. She's basically running 31" K02s in stock height TJ. Very good tread, 1yr old. Front suspension all rebuilt within last few years.

Fast forward and she comes home from classes tonight and said her jeep almost didn't stop several times, but had brakes. I go look, full reservoir, rear brakes not old enough to be bad. Front disc's look ok. I'm confused. Get in to take for test drive and instantly heard the swoosh and spongy brake pedal of bad booster.

 

[Daryl]

Yes and probably bench bleed the booster.

-Mac

How exactly does one bench bleed a vacuum booster.

 

[macleanflood]

I've always used a parts store kit and run clear hoses up into the reservoir and pumped the brakes until it stopped bubbling. Then disconnected the clear hoses and attached the proportioning valve as quick as possible to prevent fluid loss.

-Mac

 

[grabeb]

How do you bleed booster?

 

[Daryl]

I've always used a parts store kit and run clear hoses up into the reservoir and pumped the brakes until it stopped bubbling. Then disconnected the clear hoses and attached the proportioning valve as quick as possible to prevent fluid loss.

-Mac

Huh? a booster?!

 

[grabeb]

The booster doesn't hold fluid. You don't bleed a booster. At least none I've installed.

 

[hear]

He means the master cylinder, not the booster. You can swap the booster w/o opening the brake system, ask me how I know. But be aware there is an adjustment process on the booster to set what I'm going to call the "rod depth." There is a thread here where blain describes the process, I'm sure its in the FSM too. If it's set wrong it can make your brakes feel weird, or even not bleed properly.