Bad Brake Booster?

[CheepComanche]

Recently while driving I've noticed that I have to push harder on the brake pedal then I used to. Coming to complete stops, especially down hill, are very difficult. I'm assuming the brake booster has gone bad but before I replace it I just thought Id ask to see if there's anything else that could cause this. 

[schardein]

A very easy test for a failing vacuum booster, straight from a google search:

 

"To perform an easy test, turn off the car and pump the brakes 4-5 times until the brake pedal stiffens up. Then, push down the pedal and start the car. Check for a slight give underfoot. If the brake pedal stays stiff without giving slightly, the brake booster may be failing."

 

Another simple thing to check is the one way check valve in the booster.  The one way check valve is what the thick vacuum line attaches to on the booster.  

Twist/pull the vacuum line from the check valve.

Twist/pull the check valve out of the rubber grommet in the brake booster.

Now that you have the check valve in your hand, put the part that the vacuum hose attaches to in your mouth, and suck- air should pass freely.  Then blow- the valve should seal and no air should pass.

Then wipe it off (so you don't get your nasty germs on the Jeep ) and reinstall, or replace if bad.

 

You can also check to see if the thick vacuum line has become disconnected at either end, or has any cuts or holes.  

 

Check that the engine is in a good state of tune so it produces the normal amount of vacuum.  If you have a vacuum gauge, look for a steady reading of 18-20 inches at idle.

 

Have you had your front bumper off lately?  Don't forget to hook up the vacuum line to the vacuum reservoir on the passenger side / back side of the bumper (round or football shaped plastic reservoir).

 

Does your HVAC seem to only blow out the defrost?  That is a symptom of a disconnected vacuum line, or faulty/leaky reservoir.

 

Good luck and keep us posted.

[CheepComanche]

I tested the HVAC and all is good. I wasn't able to get the vacuum line off the check valve as it feels like there is vacuum pressure holding it on. I am still going to test the vacuum with a gauge but I'm not sure where to hook up the gauge. There is this T-piece that I'm not sure what its for but I thought maybe I could connect the gauge to that. 

[pizzaman09]

I don't particularly recommend this method, but I just drove to a big hill, turned of the truck and pumped the brakes five or so times.  I ended up finding that the brake boost went away and I had to lay into the pedal to get it to slow down.  So I thus determined that the brake booster was working.  

 

I was concerned myself as my Comanche has the firmest and nicest feeling brake pedal of any vehicle I own with power brakes.  It just takes a bit more force than your normal power assisted brake car.

[CheepComanche]

I just took of my brake drums for the first time and I'm glad I did. Not only were the brake shoes extremally thin, the pad material was broken off of the metal part of the shoe. So I had no rear brakes. I'm assuming this would cause me to have to use more force to stop lol. I will still check the vacuum pressure for good measure. 

[schardein]

Obvious problems should be addressed first 

 

As for checking vacuum, you want manifold vacuum, not ported vacuum.  Ported vacuum will be any vacuum ports on the throttle body itself, near the area of the throttle blade.  Manifold vacuum (not to be obvious) is anywhere on the intake manifold after the throttle blade.  The vacuum booster is manifold vacuum.  Not sure what that T-fitting is, but it is probably manifold vacuum.

 

Just a suggestion, add your Comanche's year, engine, trans to the signature line of your profile-- that way people who want to help, don't have to ask questions first.