Ok, I'm having some problems w/the brakes on my '95 2WD 3500.
I have a normal power brake booster w/the vacuum line running from there to the vacuum pump.
The truck has all new brakes all the way around as of last year, everything is in great shape.
I noticed the pedal went down quite a bit before the truck started stopping. I compared how my brakes felt to the ones on my boss's truck ('99 3500 CTD 4x4) & his were MUCH better with a LOT less pedal travel.
So, I went & looked under the hood & noticed the vacuum line ends at the booster fitting & at the vacuum pump were collapsed.
I went out & bought some new vacuum hose & replaced everything & clamped everything back together.
Now after a while the ABS & Brake lights will come on. I touch the gas for a second, lights go out, brakes are fine.
I finally had enough of that & put a piece of the old collapsed hose back on between the vacuum pump/& T fitting...same problem.
When I'm going slow, using the brakes a lot (backing into someplace etc), the warning lights in the dash will come on & the pedal will get really stiff & its' a little difficult to stop.
I'm not sure what to do...as far as I know the vacuum pump is working (cruise works fine). There's obviously something wrong w/the brakes, however I have no clue what; I'm out of ideas.......

 

It's common with the vacuum assisted brakes to use up all availible vacuum if you're braking at idle. The pump just can't keep up. About all you can do is be aware of it and idle up or add a vacuum storage tank.

If you are running out of vacuum above idle I'd look for a leak.

 

Couldn't he put a reed valve inline between the ABS vacuum canister, or whatever it's called, and the rest of the system to keep this from dropping vacuum to that box, which makes the lights come on?
I have this happen to me, but only when I am playing with the brakes, pumping them, etc. and deplete the vacuum in the system.

Chris

 

It could be that your brake booster is crapping out on you.
Mine was doing the same thing. Replacing the booster solved the problem.
you could also have a leak with one of the actuators on your ac system.
Go through the settings one at a time and go through the same steps that was causing your problem. I can't remember for sure but I believe that it was the fresh air setting that would make mine completely lose vacuum.
It would lose it slowly when I was on recirculate but it would go away completely from just getting off of the accelerator when on fresh air. My ac vents would shift to the defrost as well when this occurred.
You can also build a small vacuum tank out of pvc to give you a little reserve.

 

Thanks for the replies!
I'm hoping its' not the brake booster; doesn't look like something to look forward to changing, but oh well.
It does this prob. w/the brakes all the time. I don't really use my A/C much & just drive w/windows down & have the climate control all the way over in the blue. & I always have the other switched above it set to "OFF".
The vacuum canister idea I could live with. What all is involved with putting something like that in?

 

Biggest problem is finding space under the hood for it. Vacuum reservoirs are available from many after market sources for a around $25 or you can make your own.
All you need is 6"-12" of 4" PVC pipe, two caps and a bit of hose. Drill and tap one 1/8" port in a cap then glue it together. Find a place to mount it then tee in one hose, 1/8" will do, to any stock hose in the system.

First though I would check for leaks. Easy way to do this is to run the truck a few minutes, shut it down for a few minutes then disconnect any vacuum hose. If you don't hear a hiss there is a leak somewhere. A leak free vacuum system will hold vacuum for days, if not weeks, without the engine running.

 

I took the truck for a ride for about a 1/2 hour tonight, brought it home & let it sit for a bit. I popped the vacuum hose off at the brake booster & there's definatly a hiss.

I think I may look into a metal vacuum canister & put it on a inner fenderwell or something.

thanks!