Thanks - I'll start there then guys. Appreciate the prompt response

 

If the brakes react fine numerous times in a row - braking, letting go, and immediately braking again a number of times. with no issue - is it more likely a leak than the valve itself? And how do I go about checking for a leak?

 

put a vacuum gauge on one of the lines, and see where you are . then hit the brakes and see if it drops any. if you see less that 19 inches static, and it drops to 17 or less after stepping on the brakes, the pump is bad and needs replacing

 

Great - thanks!

 

Starting to get worse and whne the brakes were acting up I checked to see how the vent reacted and it didn't want to change from defrost to vent - guess now I know for sure what needs to be done :\
Anything in particular I should watch out for/ is going to be a pain in my ****?

 

Ok - so it has been forever - I know.
BUT I did replace the vacuum pump and a weird thing is happening.
If the truck has been off for a while, and I start it up, the brake petal is high and very stiff - with poor braking capacity. Once I have used the brake (or even pumped the pedal) 6-7 times it is softer, brakes properly, and stops good when needed - acts normally in other words.
Any idea why this is happening?

 

Cut drums can cause a low pedal, even with the shoes adjusted tight.

Also, if your park brake doesn't work, your rear brakes aren't working properly either.

 

bad booster or the one way vacuum valve on line going into the booster is bad, and you have a leak somewhere.

when the truck sits for a while take the vacuum line out of the booster. i bet there is no vacuum.
he booster should hold vacuum.

 

So after sitting the brake pedal being very HIGH and stiff without good stopping power - which then after a few uses levels out to good braking for the rest of the run could be a leak?
how does that work? I mean once the initial 'pressure ' on the pedal goes the brake acts properly for however long I drive it?

I'll have to check the parking brake but it seemed to be working (certainly had resistance) when I was pushing it last.

Could this be a problem caused by using the brakes with an almost completely dead vacuum pump - air in the brake line or .... I don't know.

but it does brake proper after those first few times - holds the pressure for the rest of the trip.

Just trying to figure out how what you suggested applies

 

if there is no vacuum, the pedal will be very hard to push and you will have not muck braking effect.

once you get vacuum to the master cylinder the brakes work the way they should.

 

The pressure IS getting to the brakes - and the vent - which it wasn't before I changed the pump.
The brakes work great AFTER the INITIAL HIGH brake pedal with STIFFNESS and not great stopping.
I seem to be dealing with the OPPOSITE of what I was just as the pump started to go.
Once the initial stiffness goes (half dozen uses ) from then on in the brakes are fine

 

but do you have vacuum in the booster with the engine off??
it still sounds to me like you have either a bad booster, or one way valve in the line going into the booster.

 

Ok - I'll look at the booster again and the rest of the line. See what results I'm getting
Thanks