I'm stumped help!

[jmorri34]

Ok I know this has been hashed over a million times and trust me when I say I have researched all the other posts and I am stumped. Here goes: The infamous hard brake pedal. I changed from all drum to all disc and EVERYTHING from the pedal to the tires is brand new. I have tested everything I know to test I. E. Vacuum,booster check valve, pushrod is straight,vacuum hose is good,proportioning valve everything. I even did every test CPP says to do on their tech site and nothing, I have to near stand on the pedal to stop. The test for a stuck proportioning valve is negative, I just dont know what to do next. I keep thinking its a bad booster but didnt save the reciept for it( I know dumb me) So I cant send it back to CPP. Anyway, I wanted to see if anyone has any other ideas before I go buy a new booster so thanks for anything!

[Longhorn 70]

does the pedal pressure required change when the engine is running/not running?
when you unplug the vacuum line to the booster, do you fell vacuum on the line with the engine running?
when you run the engine for a minute then turn it off, can you unplug the booster line and hear air rush in?
do you have a vacuum gauge that you can measure the vacuum at the booster with?

[cdowns]

pushrods clearanced? rod from booster to master cyl and rod from brake pedal to booster both need clearances

[BugzC10]

Subscribed...can't be of much help, but want to here what resolves your problem. I may change out my rear drums one day.
Also..if you do determine it is the booster, still give CPP a call. They may help help you out.
How did the pedal feel when you bled the brakes after installing every thing? Good flow of fluid at the caliper fittings?

[jmorri34]

Originally Posted by Longhorn 70

does the pedal pressure required change when the engine is running/not running?
when you unplug the vacuum line to the booster, do you fell vacuum on the line with the engine running?
when you run the engine for a minute then turn it off, can you unplug the booster line and hear air rush in?
do you have a vacuum gauge that you can measure the vacuum at the booster with?

Well the pedal pressure is the same engine off and on, there is alot of vacuum on the line when I unplugg it, I ran the engine and shut it off and unplugged the line again and no air rushed anywhere in or out. I dont have a vacuum guage but man this thing feels like its pulling alot of vacuum on it when I unplug the line. Im trying everything you said. thanks

[jmorri34]

Originally Posted by cdowns

pushrods clearanced? rod from booster to master cyl and rod from brake pedal to booster both need clearances

I dont really know much about the pushrod clearances, can you elaborate for me so I can try and check it out, Id really apreciate anything you can tell me!

[jmorri34]

Originally Posted by BugzC10

Subscribed...can't be of much help, but want to here what resolves your problem. I may change out my rear drums one day.
Also..if you do determine it is the booster, still give CPP a call. They may help help you out.
How did the pedal feel when you bled the brakes after installing every thing? Good flow of fluid at the caliper fittings?

Yea I will still call them, Pedal was nill untill we bled the brakes and stiff once it was bled numerous times. Im fairly sure the fluid is not the problem, the flow was normal when bleeding also. thanks

[cdowns]

should b somewere about 1/8 inch clearance for each one

the pedal rod is easy to see and feel
the booster to master ?? most guys put slly putty or clay on the rod and bolt everything togetther then unbolt and see how thick the putty is at rest

[jmorri34]

Originally Posted by cdowns

should b somewere about 1/8 inch clearance for each one

the pedal rod is easy to see and feel
the booster to master ?? most guys put slly putty or clay on the rod and bolt everything togetther then unbolt and see how thick the putty is at rest

Ok Ill check it out thanks!!

[leftybass209]

Maybe I'm lost on how a booster actually functions but it was my understanding that if a booster fails it's like having manual brakes. In that case my truck has no booster and certainly doesn't require a lot of force to stop. I can lock the brakes up without shoving my foot in the pedal too hard. Best of luck in your search for the answer.

[jmorri34]

Man I dont think I could lock the brakes up if I tried, I have brakes but it sure doesnt seem like the booster is working to me. I know its brand new and all but I dont think its working. The weird thing is all the booster tests turn out good but it just doesnt seem to me its working, I wonder if thats even possible

[grayw0lf]

I'm in the exact same boat on my '70 C-10. I don't think i could lock the brakes up on dry ground if i tried.

[faribran]

you dont have a pinched or crimped steel line do ya ?

[jmorri34]

Originally Posted by faribran

you dont have a pinched or crimped steel line do ya ?

No everythings brand new and bled perfectly, on the phone with CPP tech as we speak.

[Bigdav160]

What master cylinder are you running?

[Longhorn 70]

Originally Posted by jmorri34

...... I ran the engine and shut it off and unplugged the line again and no air rushed anywhere in or out. ... thanks

Do you have a one way valve in the vacuum line? It should be on the end that plugs in to the booster.

Looks kinda like the one in the pic below. If you do, good. If you do unplug the end that goes into the booster and blow in it. You should be able to. Now unplug the hose from the other end. Blow into it. You should NOT be able to.

[jmorri34]

Originally Posted by Longhorn 70

Do you have a one way valve in the vacuum line? It should be on the end that plugs in to the booster.

Looks kinda like the one in the pic below. If you do, good. If you do unplug the end that goes into the booster and blow in it. You should be able to. Now unplug the hose from the other end. Blow into it. You should NOT be able to.

Yea same one as that. I actually pulled it out and you could hear the air escape. I also checked the valve and you can only do it one way so its good too. Im at a loss. CPP is helping me pretty good to so Im testing stuff with them also

[jmorri34]

Originally Posted by Bigdav160

What master cylinder are you running?

This is the setup I have here, everything looks good but its just not working right!

[slow-1]

Originally Posted by jmorri34

I ran the engine and shut it off and unplugged the line again and no air rushed anywhere in or out.

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.

[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?

[mmiddle]

Originally Posted by Longhorn 70

Do you have a one way valve in the vacuum line? It should be on the end that plugs in to the booster.

Looks kinda like the one in the pic below. If you do, good. If you do unplug the end that goes into the booster and blow in it. You should be able to. Now unplug the hose from the other end. Blow into it. You should NOT be able to.

2X!!!! The check valve is critical.

[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!

[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.

[davischevy]

Originally Posted by jmorri34

This is the setup I have here, everything looks good but its just not working right!

Subscribed:
That looks like the same set up we put on the Blazer a while back, with the same results. We never did figure it out. We changed vacuum source, master cylinder and We finally put all the old stuff back on and it works great. The new one is laying here in a box. I know this doesn't help, but I suspect someone has built some faulty boosters. We bought our set up from a place called "performanceonline.com" and none of their troubleshooting tips worked.

[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.