Brake issues, Vacuum?

[benmgsr]

Gday all,
Another problem arising from my weekend away...

The brakes are not working well. After continued use into the camping location, the brake light came on on the dash and the brake pedal went hard and the brakes barely worked.
After putting up with it throughout the weekend, i figured it was vacuum because they work fine if i use them sparingly, but if i pump the pedal etc, they fail. Also, as i start the car, the light comes on and then slowly fades as though it slowly builds vac...

Is this right?

I bought a vac meter to measure the pressure, but cant find out what it should be... anyone know that numbers for the vac pump, reservoir etc?

Any help appreciated, thanks

 

[simonliew]

what kind of truck and mileage please?
Simon

 

[jake2far]

Vacuum should be above 20hg or inchs of mercury.
It sounds like you have a leak somewhere or the vacuum pump is failing. Pull the hoses off the pump plug all but one and attach the gauge start the engine and watch how fast and high the vacuum(actually low) the gauge should show a rapid increase in vacuum and it should go above 20 inches. If the pump tests good you need to find the leak, it could be a hose, a metal pipe rusted through, a vacuum tank, your brake booster, or a bad vacuum valve. I am sure I have forgtten something and it will be provided by another Mud member.

Good luck

Jim