So i came about this idea after going through everything else once again. The car has 2 problems. Rough/bouncing idle. And no matter how much i bleed the brake and check for leaks. They pedal has no pressure while the car is running.I can get the brakes to work if i pump the pedal, but barely. and while the car is turned off. they pedal has presure.



So i was thinking that maybe the brake booster has a leak in it to cause the engine vacuum leak (rough/boucing idle). and the brake pedal having no pressure is caused by the leak in the booster also...



So how would i test the brake booster for a leak. Put pressureized air into it to see if it leaks out???

 

2 things come to mind,



A. disconnect and plug the booster vacuum line. start and run the car, if the idle is good you have found your problem.



B. buy/rent a vacuum/pressure pump (Advance Auto carries such a pump for rent), disconnect the booster vacuum line and plumb the pump right to the metal "fitting" right off the booster. Start pumping vacuum from the booster. when you get to 10-20in/hg stop pumping and watch the guage, if the needle falls toward 0in/hg you have a bad booster.



If you find a bad booster and need another one I recommend staying AWAY from Advance Auto Parts, I'm on my 2nd faulty booster from them, but to use the lifetime warranty I either have to front $110 to order one and be reimbursed, or take my current one off for them to order a new one which puts my car down for a week.... really gay.



Hope that helps

-Pat

 

the booster should hold vacuum. pressure would be bad, its not designed for that.

 

Just like any vacuum line, it will see pressure while boosting.

 

no it does not. most of the vacuum lines do NOT see boost, which is why its important to get them in the right places. the brake booster has a check valve on it. think about it, it only works with vacuum, so they store it. without the check valve, you hit gas and have no brakes! that's bad!

 

Start the car and run it briefly.

Shut down the engine.



Remove the clamp and pull the vac hose off the booster (not from the firewall hardline).

If there is vacuum present, you'll hear a small "pop" sound as the vacuum in the booster is displaced.



In my experience, it's rare for a booster to go bad.

More likely would be the check valve in the line or the soft hoses themselves.