Vacuum Problems - No Power Brakes

[matt-jenkins]

Posted this today in the Powerstroke section but havnt gotten any replies and need help ASAP

Friday I came to a stop and I got the classic Hard Pedal syndrome, I checked the vacuum line running across the top of the motor to the T on the drivers side fender well and had no suction. I replaced the Vacuum Pump and now have vacuum but no brakes. Next I pulled the Brake Booster and installed a Reman Unit from NAPA, Still no brakes. Today I am going to start tracing Vaccum lines and checking all the T's and Fittings.

Any suggestions of where to start or what parts are more prone to failure than others? Also, Does the new Brake Booster need to be adjusted before you drive? I installed without messing with the shaft but I have read that they are adjustable and sometimes require it.

Thanks!

 

[matt-jenkins]

I checked the lines and didn't find any leaks, I also plugged line from vacuum pump directly into the booster and still had no luck, what should my next course of action be?

 

[lindstromjd]

So your new vacuum pump is working, but your booster still isn't working? Last time I had a problem, I replaced the booster too and everything worked fine. I think your next step should be new lines.

 

[79jasper]

Jack up one corner at a time and make sure the brakes are actually working. Could be a blockage somewhere. I don't think the rod adjustment is your problem.

 

[matt-jenkins]

Jacked up the rear end and the brakes work, I cannot find any leaks anywhere in the lines. Could
It be the master cylinder? I'm really at loss of what my issue could be

 

[79jasper]

Did you check the front also?
You could've received a bad booster. It happens. Do you have a manual hand vacuum pump, like a mityvac?

 

[matt-jenkins]

Ok so here is an update
I replaced the master and flushed the entire system with new brake fluid, no change
I did install a second reman booster as the first reman I had wasn't building vacuum, still no change.
I had good fluid pressure when I was bleeding, the truck doesn't pull at all when I brake so all 4 corners are working.

I really am at a loss, should I try replacing the RABS modulator?

 

[79jasper]

Is your abs light on?

 

[matt-jenkins]

The ABS light comes on intermittently and the e-brake light is almost always on

 

[lotzagoodstuff]

Silly question: have you checked the little check valve on the booster itself? I'm guessing you got a new one with the new boosters, but if you reused the old one, you could have a problem there.

Good luck, nothing more frustrating than swapping bad parts and not solving a problem. I always cover the problem generously with beer, but it doesn't always fix the problem.......

 

[79jasper]

When it comes on, don't turn the truck off. Then flash out the code.

 

[matt-jenkins]

I have replaced the check valve, and how do I get the abs/e brake light code?

 

[79jasper]

If you give me a few days, I'm working on a write up. You have to have the RABSII brakes though.

 

[matt-jenkins]

Second question then, how do I know if I have RABSII or not?

 

[79jasper]

I'm not totally sure. I'll do some searching when I get home.