brake issues

[jonathan]

when i put my truck in reverse the pedal is hard as a rock when im going forward if i push the brakes 2 they get hard again. then it goes away after a couple of seconds. i hear a hissing sound sound when i push the brakes and when i shut the engine off. all of the vents work right. one more thing the parking brake light turns on and off at will, i think its the sencer.

 

[argve]

sounds like the vacuum pump is letting you know it's going to need replacement.

Signs of that - rock hard pedal - meaning no vacuum assist.
brake light on - sensor detects that vacuum isn't strong enough so turns light on to alert you of problem.

 

[sassyrel]

as travis said--the hissing sound tho--sounds like the brake vac diaphragm leaking

 

[jonathan]

as travis said--the hissing sound tho--sounds like the brake vac diaphragm leaking

are talking about the brake booster

 

[jonathan]

i have mity vac can use it to see if booster is lossing vac pressure? how much vac should i have at the booster and how much vac at the vac pump? so low vac will cause the parking light to turn on and off? were can i get a cheap vac gauge tester thing? thanks

 

[jonathan]

i got a vac tester. i have 28 psi at the booster and 28 psi it the vac pump but when i turn the engine off the hissing is coming from the passenger side by the inter fennder. is there a vac resseve contianer? i think what is happening when i push the brakes a couple times it runs out vac = rock hard brakes. what do you guy think?

 

[smolkin]

The vac system isn't really complicated, try tracing all the lines. I know on my truck I've had to replace the lines going to the heater door, the factory ones are hard, brittle plastic and can have very small cracks.

 

[hesutton]

Like smokin said, you are leaking vaccum somewhere in the system. If the hiss is coming from the passenger's side, start at the vaccum pump and follow the vaccum lines until you find the source of the leak.

Heath

 

[jonathan]

i just got done mity vacing all of the lines they all held pressure but it bleed off very slowly but when i pulled the hose from the booster and hooked up the mity vac to that hose it held pressure without any bleed off. is there a way to test the booster for a vac leak?

 

[gatorman21218]

Another way to check for leaks is to run a piece of hose directly to the pump and to the booster. I dont know if you have an automatic or not, and if so how the lack of vacuum will effect it.

BTW to be correct, Vacuum is measured in inches/mercury or in/hg with 30 being a perfect vacuum.

 

[jonathan]

its a automatic and shifts perfect now that added four qts to top it off thats a differant story. when i hold the brakes i hear a hissing it sounds like its the booster and when i let off the brakes it goes away

 

[jonathan]

should i just get a new booster its only 80 bucks

 

[hesutton]

its a automatic and shifts perfect now that added four qts to top it off thats a differant story. when i hold the brakes i hear a hissing it sounds like its the booster and when i let off the brakes it goes away

You should not hear any vaccum leak when using the brakes. If it is hissing at you, it is leaking. I'd replace it.

Heath

 

[jonathan]

thanks ill get one in a few weeks when money allowes