Brake booster gone bad?

[GO BIG OR GO HOME]

Pulled the 99 out after sitting for for about 4 or 5 months to drive it a little and it had a really spongy pedal. Checked the brake fluid and all was well so I decided I'd bleed them. All good there too. No pedal improvement after bleeding. Is this the booster gone bad or what?

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[swinky]

Probly master cylinder

 

[GO BIG OR GO HOME]

Oh ok thanks. Any way of checking the mc or booster?

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[Dmstrucks02]

Did you check the power steering fluid?
Maybe flush it too

 

[GO BIG OR GO HOME]

Did you check the power steering fluid?
Maybe flush it too

No I didn't. I will check it first thing Monday morning. Thanks

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[Big Angry Hillbilly]

Spongy pedal is air in the system or excessive travel - caliper slides seized up, back brakes way the hell out of adjustment if drums, etc.

 

[GO BIG OR GO HOME]

Ok guys this thing is driving me crazy. Here's the deal as of now:

Pulled it in the shop this morning. Power steering pump was full but really nasty and black. When you mashed the brakes I noticed I could only get about a half turn out of the steering wheel before it locked up. So I figured the pump was bad and changed it out with one from oreillys. Brakes and steering felt great for about 5 minutes then back to the same deal. Truck still didn't want to stop at road speed. No steering while foot on brake. Pedal has pressure but will travel to floor. So swapped the new pump for another new pump. This time after swapping the pump I flushed the system from the booster till I had nice and clean atf in the system. Truck stops a little better but not near what my other trucks will. Pedal will still travel to floor under hard braking but will then kick back up and have a good feel to it then until you let off. Still have no power steering while foot on brake. Can only get about a half turn. Am I doing something wrong? Did I get a dud pump?

Please Help!!!

Edit: truck is a 99 250 super duty 7.3 4x4

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[Dmstrucks02]

I was thinking the Fluid change would do it for you
Maybe someone will have another suggestion

 

[GO BIG OR GO HOME]

I was thinking the Fluid change would do it for you
Maybe someone will have another suggestion

You and me both! Hopefully someone else chimes in that's maybe experienced this.

Please help. Really need to start using this truck next week

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[bluedge8]

the booster is just the symptom, you are using so much boost to try and stop the truck that it is using all of your pressure from the pump. You have a bad master cyl, it is bypassing internally. Can you step on the pedal to where it feels like a good amount of pressure, then hold that same pressure and see if the pedal drops within a second or so?

 

[GO BIG OR GO HOME]

the booster is just the symptom, you are using so much boost to try and stop the truck that it is using all of your pressure from the pump. You have a bad master cyl, it is bypassing internally. Can you step on the pedal to where it feels like a good amount of pressure, then hold that same pressure and see if the pedal drops within a second or so?

When I mash the pedal you get some decent resistance about half stoke but you can press through it straight to the floor and the resistance never changes. If I press the pedal 1/2 to 3/4 stroke and hold the pedal does not drop any further. Just a 1/4 stroke of the pedal kills my power steering. I'm so frustrated with this

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[GO BIG OR GO HOME]

Ideas anyone?

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[GO BIG OR GO HOME]

Ok here's a little more info on the symptoms:
Took it for about a 40 mile drive this afternoon running 60mph with od off just trying to bleed any air out. No foam or bubbles in ps fluid. Truck will stop but the distance is about double what it should be. When I brake hard the pedal goes to the floor then kicks back up hard then is spongy. When stopped you cannot turn with pressure on brake pedal. As soon as you release the pedal it turns fine. No whining from pump. I do have steering while braking going down the road.

All this is after 2 reman ps pumps and fully flushing the system with new atf.
Any help would be greatly appreciated guys!!!

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[bluedge8]

Have you changed the booster?

 

[GO BIG OR GO HOME]

Have you changed the booster?

No I have not. I will if that's what needs to happen but I'm not big on just throwing parts at a vehicle without knowing why I'm doing it... if that makes sense lol. Will the booster effect the steering? I know the pump affects the brakes but didn't know if it worked the other way round. My biggest hang up about all this is after I changed the pump the first time everything worked great! Brakes and steering were perfect for about 5 minutes till that pump grenaded. When I changed it the second time I flushed the fluid to avoid killing another pump. After install and flush I was pretty much back to square one. I did the flush with engine running. Is this correct?

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[GO BIG OR GO HOME]

Bump

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[7.3 Cowboy]

I had a caliper blow apart and how no brakes but my steering worked just fine so I don't think it affects steering

 

[TyCorr]

Aaaand this thing isnt puking brake fluid all over the.ground or.bottom.of truck?

 

[GO BIG OR GO HOME]

I don't have the busted caliper. But to answer your question anyway no I have no brake fluid coming out anywhere

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[TyCorr]

Whats that box behind the headlight? Do those.go bad? I believe its a proportioning valve.

It sounds like the master cylinder is chitting the bed...