LEAKING POWER BOOSTER

[ROBERT MITCHELL]

OK i have an 88 model with a 5 speed and carbed. I upgraded my power brake booster to an Aspire booster and just recently i have heard a vacuum leak from under the dash on the drivers side and when i apply the brakes it stops. So i am assuming it is the brake booster. Am i right on that? Then i also wanted to know if that would affect my gas mileage since that is essentially a vacuum leak, it seams to idle very rough and it stumbles really bad if i am rolling down the highway at about 65 mph and get off the gas and then reapply is when it happens. Also what will it hurt if i keep driving with the booster leaking? Thanks in advance for any info on this!

[FestYboy]

fix it NOW, you're causing a lean condition that the ECU can't cope with. lean conditions burn things like valves... which is bad.

[georgeb]

I repaired a Buick unit once with an O ring on the plunger. Depends on how hard it is to separate the 2 halves.

[ROBERT MITCHELL]

Oh so you are saying i can fix the booster itself or should i just go find another one from pull a part and just replace it?

[georgeb]

Try to find one first.

[ROBERT MITCHELL]

Ok i will do that first, thanks!

[ROBERT MITCHELL]

Well i went and found another brake booster and replaced it and no dice. First off it died on me Friday night on the way home and i couldn't figure out what was going on, so i tinkered around a bit while in the middle of the road and come to the conclusion that it was getting way too much air, so i blocked the breather to restrict the airflow and it ran and idled, and i was able to limp home. So after that i just assumed the the brake booster had gotten worse and just needed to be replaced ASAP. Now back to the booster replacement, so i get it on and try to start it and still no dice so i starve it for air and get it to idle and check around for other vacuum leaks and i couldn't find not a one! So now i am really at a loss for words. I even tried adjusting the idle fuel/air mixture screw and still will not idle on its own. If i get it to start without starving it for air i have to keep reeving it to keep it running. Can this be a fuel pump issue or is there something else that someone can suggest i try. Thanks!

[FestYboy]

not enough flow through the carb to draw fuel into the venturi...? try this if you're SURE there are no onther vac leaks: pinch off the fuel return line at the pump. see if you can get more pressure into the bowl.

[ROBERT MITCHELL]

Ok so when i try this, and if it runs and idles on it own would it be safe to say its the fuel pump? Thanks for the info, i may not be able to try anything till this weekend but when i find something out i will post it. Any other suggestions would be greatly appreciated! Thanks!

[ROBERT MITCHELL]

I went out and gave it a try (pinch off the fuel return line at the pump) and still the same thing. So i'm totally lost right now, is there anyone out there that can shed some light on this for me? Please help!!

[FestYboy]

you've got to be pulling air from somewhere then, OR the anti-diesel valve is stuck closed, but thats a rare occurance.

[bravekozak]

Is there sufficient vacuum to the brake booster?
Pull off the hose and feel with the engine running.
Is the one way valve in the vacuum line to the brake booster stuck open?
Shut the engine off and make sure you can't suck backwards toward the brake booster.

[ROBERT MITCHELL]

Festyboy: yep its definitely pulling air from somewhere, i even used a mechanics stethoscope to try to find a leak and still nothing.
Bravekozak: i think the booster is getting plenty of vacuum but i have not pulled the hose off with the engine running, but i did check the one way valve in the line and it works properly.
So i am going to get deep into it this weekend and find out what is going on with it but if anyone has some more ideas they would be greatly appreciated!

[FestYboy]

ok, the stehoscope won't help much here, you need a long piece of fish hose or the like to find this one... also double check UNDER the intake at the 2 coolent temp driven solenoids, they tend to crack...

[ROBERT MITCHELL]

OK i will check those as well and hope to have it back up and running this weekend.