I'm stumped help!

[steelhorse]

Sounds like a bad booster. With all the crap coming from China these days bad new parts is real common.

[jmorri34]

Originally Posted by slow-1

I think you shoud hear the pressure/vaccum equalize when you did this...almost like popping open a cool one.

Seems to me like there is an internal leak in the booster.

Yea, thats what I heard, it was like a pshhhhh sound lol

[jmorri34]

Originally Posted by Longhorn 70

OK so if there is a check valve and you don't hear air rush when you remove the vacuum check valve from the booster, the booster isn't holding vacuum or there is no differential betweek the chambers of the booster.

There isn't a decal or plastic or anything covering the BACK side of the booster is there?When you unplug the vacuum line and from the booster and the engine is running, do you hear a mad rush of air going in to the disconnected end of the hose? Does the engine idle change?

When I unplugged the valve I heard a rush of air so that is that, I didnt see any decal on the back and when I unplug the line with the engine running there is definately a change in engine tone for sure!

[jmorri34]

Originally Posted by Ole Greenie

Well, after 3 months diagnosing my brake issues...which are mostly unrelated...I also agree that the booster may be suspect. The booster is rarely the issue though. I too have a hard pedal but that is because I have a BBC and I was looking for the clearance from the lt. head so I got a double booster. I digress...but either the internal diaphram is working or not, the check valve is working or not, or you are not pulling enough vacuum. I had to dedicate a big hose from the intake to the booster...all by itself.

Now if you have this dedicated line, and all else checks out then I'm stumped too. I'm sure you have checked but the front line out of your PV goes to your Ft. brakes and the rear accordingly. I'm inclined to think your booster is suspect, That's an 11" booster and it should do really well in boosting the line pressures!

Yea I hear ya, Im thinking the booster too, I have a line running from the intake directly to the booster and if I put my finger over it the vacuum is such I cant even shake it off so I dont think its the vacuum. The check valve is good , all the rods and linkage look good to me so Im lost. Thanks for your info!

[jmorri34]

Originally Posted by slikside

Have you tried this booster test:

With engine off, press/pump pedal firm and hold.

Start engine.

If pedal moves toward f floor, booster is working, if not, it isn't.

Qiuck, simple,easy, decisive.

Yup tried it and the pedal pumped up right, but when I started the truck it never moved. Now that should tell you the booster is not working but all the other booster tests show the booster to be holding pressure so I dont understand!

[jmorri34]

Originally Posted by oldspowered67C10

Id be willing to bet its a bad booster, those CPP boosters are a crap shoot at best, I had 2 bad ones in a row, finally got tired of it and got one from the junkyard, works great now.

Ye I am completely in agreement with you. But I dont want to go drop 100 bucks for another booster and it not be the problem, but looks like that may be what I have to do!!

[Longhorn 70]

Originally Posted by jmorri34

Yup tried it and the pedal pumped up right, but when I started the truck it never moved. Now that should tell you the booster is not working but all the other booster tests show the booster to be holding pressure so I dont understand!

There is a valve in the booster which blocks the source and allows atmospheric pressure in at the same time. If the air cannot get in or there is not enough vacuum on the M/C side you have a hard pedal.

OK it doesn't work now, right. Try this for kicks but do not drive the truck while doing it.

Take the master cylinder off of the booster. Don't disconnect the lines.

With the engine off, press the pedal all the way to the floor SLOWLY and let it up quickly a few times.

Put the cylinder back on and try the engine off/on test again. It may not do anything for the good but it may help open the atmosphere vents on the back side of the booster.

[jmorri34]

Originally Posted by Longhorn 70

There is a valve in the booster which blocks the source and allows atmospheric pressure in at the same time. If the air cannot get in or there is not enough vacuum on the M/C side you have a hard pedal.

OK it doesn't work now, right. Try this for kicks but do not drive the truck while doing it.

Take the master cylinder off of the booster. Don't disconnect the lines.

With the engine off, press the pedal all the way to the floor SLOWLY and let it up quickly a few times.

Put the cylinder back on and try the engine off/on test again. It may not do anything for the good but it may help open the atmosphere vents on the back side of the booster.

Ok I will try this and see how it goes, at this point im up for trying anything lol!! thanks for the help. 1 question, once I slowly push the pedal down I can let it back up right afterwards right?

[Longhorn 70]

Yes.

Just push it like you are doing a regular stop. Not like a panic stop. If it's still hard to press the valve isn't letting atomospheric pressure in the back side. If it is easy the valve isn't letting vacuum into the front chamber.

[jmorri34]

Originally Posted by Longhorn 70

Yes.

Just push it like you are doing a regular stop. Not like a panic stop. If it's still hard to press the valve isn't letting atomospheric pressure in the back side. If it is easy the valve isn't letting vacuum into the front chamber.

Ok thanks Ill check it out. Sounds like either way that means the booster isnt working right from the answer I get am I understanding that right. And once again thank you for helping me

[Longhorn 70]

You are very welcome. This board is great for getting helpful suggestions. They have bailed me out many times.

Best of luck buddy.