brake trouble need answer ASAP

[93cc7.3]

so i pull into my drive way and almost hit the garage because i lose power assist only going like 5mph.

the brakes have been kinda like this since i bought it but neeeever like this

if i push the pedal the truck stops pretty well but if i hold it itll sink to the floor

still keeping the truck stopped so my question is is this a vac pump problem for a booster

here is the tests i did

pump the brakes more than 3 times spaced a second apart and itll lose power assit but hold it itll sink

took the vac line off the booster put my thumb on the end of the line it barely kept my thumb sucked to it

also with the line off the pedal was pretty frim but still sank took ALOT more force though

i need this truck tomorrow to go to work at 6am i have a spare vac pump but dont want to waste time if its the booster

 

[RANOVRU]

No leaks anywhere? I had a brake line bust on me one time pulling into a 7 Eleven. Just random.

Make sure to check good for fluid anywhere (wheel cylinders, callipers, lines). If there arent any leaks than its got to be either the booster or MS.

 

[93cc7.3]

no fluid loss and the brakes hold power just seems to lose power assist

 

[sle2115]

I'd throw a vacuum gauge on it and see what you find.

 

[Michael Fowler]

See if this link works:
http://arrc.epnet.com/autoasp/framerq.asp

 

[93cc7.3]

no vac gauge

 

[93cc7.3]

See if this link works:
http://arrc.epnet.com/autoasp/framerq.asp

asking for login

 

[Cucamongan]

it sounds like your Vacuum assist Brake booster is doing its job. I suspect you Brake Master Cylinder is leaking internally and causes the pedal to sink

 

[93cc7.3]

it sounds like your Vacuum assist Brake booster is doing its job. I suspect you Brake Master Cylinder is leaking internally and causes the pedal to sink

ya im not sure when i did the 3 pumps the pedal gets hard then falls maybe both could be bad

 

[bghnkinf350]

Sounds like you might need the vac pump. A gauge will show for sure, but it sounds like you are not getting enough if it is not holding your thumb onto the hose.

If you have the spare, what can it cost besides your time. Is the pedal sinking to the floor, or is it going to the same level where is normally goes with the vacuum assist?

 

[93cc7.3]

With the pump hooked up when u push the pedal it makes a buch of rushing air noise then gets firm and sinks from there

 

[typ4]

Your master is bad if the pedal sinks, booster could still be bad, they dont last forever, especially on rust belt trucks.

 

[Black dawg]

like said above, if the pedal sinks with no fluid loss, bad master or rabs valve.

 

[GOOSE]

Mel has stated it before and I agree, a vacuum gauge plumbed into the cab is a great idea. Learn how it behaves and know when there is a problem because it is not behaving as it should.

 

[93cc7.3]

old vac pump only put on 5 inches of vacuum new used one 25 inches of vacuum brakes work better now still sinking but thatll be fixed soon atleast i have power assist back