Brake booster question

[Wbruiser2]

I've just replaced all the brake lines, proportioning valve, front calipers and brake hoses, and the master cylinder was replaced a month or so ago. I've bled everything and no leaks any where. The brakes work but they are very soft and but I can pump them up. I took the vacuumn hose off the intake (the one that goes to the brake booster) and can suck air through it continously. I believe the brake booster is bad but the symptons (in my opinion) don't necessarily point to the booster other than the air flow. So does anybody agree that is the brake booster or am I missing something? Thanks.

 

[dustybumpers]

When you said it will pump up, That tells me that air is still in the system.

I just bought a new master for one of my trucks, and it wouldn't bench bleed.

Just because a part is new don't mean it's ok. I would try bleeding it again, and go from there

 

[m78]

You shouldn't be able to suck air through the booster like that.
A vacuum leak like that would make the engine run real bad also.

 

[Mil1ion]

 

[Workin' Rig]

My 89 had a bad booster and you could hear a continuous "whoosh" sound when the pedal was applied and it wasnt spongy, just felt like you were pushing air.

 

[Wbruiser2]

I replaced the rear wheel cylinders and all the hardware yesterday. They weren't leaking but I don't think the adjusters were working. I cleaned everything up (took the adjusters apart and lubed them) inside the drum a few months ago and adjusted the brakes. When I pulled the drums off yesterday there was no drag at all them. I broke a wheel stud in the the process so I'll replace that this evening and bleed them some more and see what happens. Hopefully that fixes it. If not, the only thing I haven't replaced is the booster... Thanks for the replies.

 

[Wbruiser2]

Well... I got it all back together and bled and bled and bled some more... The pedal is still soft but it doesn't pump up anymore. After I turn the truck off and wait a few minutes and hit the brake pedal, it's hard as if the vaccumn leaked out and has no assist from the power booster. Also, it seems after it warms up, I put it in gear while holding the brake (the engine vaccumn drops accordingly) and it either stalls or just about and leads me back to the booster as the culprit. Its the only component left so I guess I'll change it out...

 

[Mil1ion]

I gave you the method of testing the booster. Did you not perform that tests ?

Also check the check valve

 

[Wbruiser2]

The brake booster had some vaccum leaks and after I replaced it the pedal just stayed soft. I had a lifetime warranty on the MC so I swapped it and now all is good. It stops on a dime