Guest BrandenZ Posted June 21, 2004 Share Posted June 21, 2004 I've been lurking on the boards for a while now and just recently came across the "right" Z to kickstart a project. Though rust-free, it isn't without problems.. one of which being the brakes. They are the big suck! I have to jam the pedal nearly all the way to the floor to get any pressure. They will, however, lock up if I really stomp on it.. but there just isn't any modulation at all. I've already tried bleeding the system. Of all my searching, the best I could come up with was that maybe the booster went out. Turns out the vacuum servo unit I've got on my car is totally missing any connection from what appears to be the vacuum line. So I'm thinking gee.. no vacuum on a vacuum unit.. no wonder! However, I'm not entirely sure that I'm correct I tried tapping in right in the center of the intake manifold.. it didn't seem to help the braking any, but I did notice that my idle would drop dangerously low whenever I stood on the brakes. Any ideas and/or suggestions would be great! It seems like this vacuum line may be the trick, but hooking it up to what I think should be a perfectly legitimate vacuum source doesn't seem to make a difference. Perhaps the booster is shot afterall? Then again, I have no idea where I'm supposed to hook up this vacuum line anyway. Thanks! Glad to finally be not only a member, but an owner as well! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 21, 2004 Share Posted June 21, 2004 Sounds like the diaphragm in the booster is dead. If the booster leaks then you'll be sucking air without fuel when you step on the brakes, basically you have a massive vacuum leak. If that's the case, just get one from a jy or put up a wanted ad here. The stock vacuum line to the booster has a one way valve in it. When you pull the line off the vacuum you can hear it go Psssshhhh. If you don't have the check valve in your vacuum line then I suggest you get one and test it out. Just start the car and the vacuum should suck the diaphragm, then turn it off and pull the hose, and you should hear the air rushing into the booster as the diaphragm relaxes. Quote Link to comment Share on other sites More sharing options...
240hoke Posted June 21, 2004 Share Posted June 21, 2004 I would go ahead and buy a new one, they arent very much money and you get a gaurentee. Plus your brake system is something you wantr right. I got a rebuilt one from autozone for like 80 bucks or somthing i think. Anyhow when mine went out the pedal got really stiff. Which is what should happen when the vaccum booster goes out. Your brakes should feel extremely hard to push on and the pedal should hardly go down. Also your engine will rev up from the vacum leak or run like crap. IMO Your mastercyinder is bad and leaking. Ive had this happen several times Anyhow when this happens your brakes will get very mushy and your pedal will eventaully go to the floor, but you will still have some brakes. An easy way to check this is to pull the master cylinder back from the booster and check for break fluid. Replace as nessary (go 15/16" it is was me, so you are set for future mods) Good luck -Austin Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 21, 2004 Share Posted June 21, 2004 Absolutely you need to replace your booster. Quote Link to comment Share on other sites More sharing options...
Guest BrandenZ Posted June 21, 2004 Share Posted June 21, 2004 The stock vacuum line to the booster has a one way valve in it. When you pull the line off the vacuum you can hear it go Psssshhhh. Makes sense. Where exactly is the stock vacuum line? The engine in this car was pulled, rebuilt, and dropped back in with just the essentials, so I have a lot of "outlets" literally just tapped off with bolts or blocking plates. I'll try to snap a shot of it later and host it. I tried connecting the vacuum line to the middle of the intake manifold, which caused the low-idle under braking condition (vacuum leak). I also tried connecting it to something that was tapped off all the way on the far right side of the intake manifold, which caused no such leak under braking, presumably because it's after the air has already flowed thru all cylinders. Anyhow when mine went out the pedal got really stiff. Which is what should happen when the vaccum booster goes out. Your brakes should feel extremely hard to push on and the pedal should hardly go down. This is exactly what I'm experiencing. It's really hard to push on and I have to really nail it to get firm pressure. If I stomp on it real good I can still get the brakes to lock up, but if I hit it with 'daily driver' pressure I get virtually nothing. Replace as nessary (go 15/16" it is was me, so you are set for future mods) I'm strongly considering doing the rear disc conversion. I sort of already figured that since I had a booster problem and needed to swap it, I'd go ahead and swap to the 15/16" to prep for the conversion. Where can I pick up one of these? Is there a parts store online you'd recommend I buy it from? Anything else you guys would recommend I replace along the way? Booster, 15/16" master, and stainless steel lines should cover it, no? Quote Link to comment Share on other sites More sharing options...
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