I have a bad vacuum leak coming from somewhere, and I believe it's the brake booster. I don't know how to test the thing for vacuum, so I can't confirm this for sure. However, I can hear the leak whooshing anywhere above 500mmhg of vacuum from the driver side dash and there is a definite variance in the sound when I push the brake pedal, also accomanied by a squeakling sound from the pedal as well. Also, with break applied at a stop, the thing idle's super lean, and almost dies out. The main vac line to the booster is in good condition, and the check valve in the line works just fine.

Has anyone else had a problem like this? How can I test the booster for vacuum, just put a pump onto it and see if it holds pressure?

 

spray soapy water on the suspect lines and look for bubbles. especially check where the brake booster line hooks up to the UIM.

 

The factory service manual has a check for this. BRAKE section.

On the whole, get the engine hot and idling. Then shut the engine off. Then step on the brake pedal to see if there's any action there. You should be able to tell. I mean step on it several times. You should be able to get seveal pumps of the pedal before the pedal gets rock hard.

Or, disconnect the brake line. Plug the line. Start the engine and see if your idle is better or not. You get the drift.

From your description, it sounds like your brake booster is kaput.

Or if you have a MIttyVac, pull a vacuum on it like in the jpg attached. It should hold vacuum. If it won't its bad.

Here's a sample out of the FSM. Easy to check out. Many variations of how.

 

Thanks, I applied vaccum to it and it definitely didn't hold anything, so I'm lookin for a new booster....

 

I think there's a rebuild kit for it. Then again..........junkyard one will do just fine. IF the right year/model is picked out.

APPLE out in Kennedale used to have several RX. I'd wage you could get the whole booster and brake master cylinder for thirty bucks. Or there is a place on the same hwy, but closer to the loop who's name escapes me. RX heaven or the like. You have to exit off a side road and drive a quarter mile to see it. Not visible from the hwy. That place is a bit higher in prices. A drivers side window cost me 45 buck from there.

 

It's Mazda- Nissan Heaven just off Mansfielf Hwy. Same hwy as Apple. See yellow pages.

 

Yea I've been over to Mazda Heaven before, I forgot about Apple though, I'll swing by those guys tomorrow, thanks!