Micaiahfied

ok so i'm sure a lot of you have seen the many brake problems i have posted. i'm pretty sure that all that is sorted out... now it feels like i don't have sufficient vacuum. if i slam on the brakes it's like they are not power assisted. if i just lay my foot on them is slowly has the power to stop it. also it takes 6-8 seconds to switch when i change the aid/defrost/heat. i bought a vacuum meter and it showed 21hg that is taking off the main line to the booster and checking it. and before you answer brake booster is brand new. any ideas what is up?

A-Poc

21in-HG sounds right. I tested mine not too long ago and it says it shouldn't measure any less than 10in-HG. You've got lots.

Mike

flashgordon

My ex.brake req 15 to turn on and when i am idling is a 14 so 21 sound grate!
Make sure that there is no kink in the line up from were you are testing right now.

Did you notes any oil resadue in the line, i beleave that was a 94 and newer probem but with that kind of vac. and you heater vac being so low theres got to be some kind of restriction there some wear.
I only have 15 and my heater controls work grate......Got to be a colapced or pinched or somtheing there.

You'r close just keep on surching

Micaiahfied

ok so i am back... i left it over night and didn't get to work on it until 2:30 today. since i had tested the line where it went into the booster i figured that the leak must be after the booster but still effecting it. well i went to take off the line that feed the heater controls and i heard that little psssssst sound... it had held vacuum all night long! now i am at a loss, does this mean that the new booster is gone? but if it were gone wouldn't the air leak out of it? like i said if i let me foot sit on the pedal it works it's way in and you can really feel it apply the (powered) brakes, but if you want to apply them fast good luck! i know i can leg press well over 500# but it shouldn't take that to stop this thing!

edwinsmith

Is it a new booster or a rebuild. If it's a rebuild take it back and get a good one. I'm not sure but there may be a check valve that keeps the vacuum in the HVAC controls from leaking back overnight.

ON my car there is a big vacuum can that stores vacuum to operate the HVAC stuff during periods of Low vacuum. This wouldn't be a problem on diesels though so I may be all wet.

The booster should have vacuum on both sides of the diaphram until you step on the pedal this lets outside air into the pedal side to assist pushing the pedal down. When you let up the vacuum is again let into the pedal side. If the valves are messed up strange things will happen.

Edwin

Micaiahfied

the valve that sticks off the booster has 3 connections. 1st is for the line in, the 2nd is for the heater controls and the 3rd goes to some kind of sensor on the driver fender. that sensor is broken on my truck so i have the 3rd one just blocked off. how do i check to make sure that the booster is the prolem? is there a way to check the valves you are talking about?

Falcon1

I think the one on your fender is for your speedcontrol does your cruse work?
Check thst could be loosing from there.

Greg

Micaiahfied

no cruise on this truck. my 92 has cruise and has a splitter to run vacuum to both the cruise and the sensor on the fender. and i don't even have the sensor hooked up, i just left the cap that came on the valve there.

edwinsmith

I don't know how you would check the valves but if you have eliminated all sources of vacuum leaks and you stiave a problem then it's most likely the booster.

Go to the parts store and get some of those rubber caps for vacuum lines and plug off the HVAC and the vacuum sensor which is over by the fender. It's a little roundish thing with the vacuum line, a plug and wires. If you have a cruise control which runs off the vacuum then plug that off as well.

Edwin

flashgordon

I agree with Edwinsmith but if you have a restricton in the line some weres, the vac could drop of fast when the vac buster is aplyed.

dus your heater controls work fine when your not pushing on the brakes?if so i would bet on a restriction.

Didn't you say that you brake light stay on all the time? is it still on now? The line that you pluged off is a sensor to turn on the brake light if the vac. get below 10, it dusn't do any thing but turn on the light....that i now of.

edwinsmith

That sure sounds like a vacuum problem to me. If that sensor is complaining that's where I would look. Of course the sensor could be bad but I suspect a leak somwhere or perhaps a restriction.

If you are developing 21" of vacuum at the booster then you would have vacuum inside the booster for one powered stop. After that, if you had a restriction the vacuum wouldn't be restored quickly enough and subquent stops will be less powered. Also, is the vacuum pump in good shape?

Edwin

Micaiahfied

ok, i hooked the vacuum gauge to the spot on the check valve that is supposed to go to the sensor, stuck it out the hood and under the wiper and i could pound over and over change the heater and whatever i wanted and it didn't drop below 15 no matter what i tried. i think that the remanned booster is bad, they are bringing another one it for me. it's just wierd, it's like the check valve isn't letting the vacuum into the booster fast enough... actually, not really then the first hard stop would work well... help, i'm still confused.

Clunk

You might try checking the vacuum off the AC/Heat port on the check valve then see how fast it drops when you step on the brake pedal while the engine is idling. The booster replacement fixed the hard brake pedal my '92.

flashgordon

At this point i would say that it has to be the vac booster!
from what you have tested it's the only thing that makes sence.

Clunk

Ain't that something, you posted while I was probably checking my spelling I guess. I'd go with another booster too.