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Old 04-18-2012, 08:32 PM   #1
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Help: Not enough vacuum, brakes suck

I've been chasing my tail on an issue with my brakes and I think I might have found out what I need to do to fix them.

Quick recap on the scenario:

-LS1 brakes front/rear
-LS1 master cylinder
-brand new fluid

I can't even lock up the brakes on the car, I used to before I did my engine swap though, and I'm thinking that the fact that I ditched the vacuum ball when I swapped engines is what is causing my issue.

My vacuum is only 11lbs, and should be ~20lbs or something like that.

My dad's friend that's a mechanic said to buy a small generic vacuum ball from summitracing or something and "T" it into the vacuum hose going from the booster to the back of the intake manifold. Is this probably what is going to fix my issue? Did I cause this on my own by getting rid of the vacuum ball on the car?
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Old 04-19-2012, 12:08 AM   #2
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Re: Help: Not enough vacuum, brakes suck

i got rid of my vacuum ball a while back when trying to troubleshoot my map sensor and didn't notice any difference in the brakes. iirc, all the ball does is store vacuum for using the brakes once or twice if the engine is not running and doesn't do anything during operation.

does it take more effort to press your brake pedal? if not it is not a vacuum related issue.

Last edited by 87zjeff; 04-19-2012 at 12:12 AM.
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Old 04-19-2012, 08:18 AM   #3
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Re: Help: Not enough vacuum, brakes suck

Yea it seems a little stiffer. Not rock hard or anything.

The cam has a lot of overlap too, which makes me think not having a vacuum canister is not a good idea.
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Old 04-21-2012, 12:43 AM   #4
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Re: Help: Not enough vacuum, brakes suck

I have a 66 chevelle with a pretty big cam, and not much vacuum. I went to the junk yard and pulled a vacuum pump from a 80's or 90's caddy. They all had vacuum pumps, some sunfires and cavelier's too. They have a regulator too, they go off and on as necessary and keep around 20" of vacuum. Just wire it up to the ign switch and a vacuum hose to the booster.
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Old 04-21-2012, 11:11 PM   #5
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Re: Help: Not enough vacuum, brakes suck

Got any pics of it mounted??
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Old 04-22-2012, 04:14 PM   #6
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Re: Help: Not enough vacuum, brakes suck

Looked at my dad's 04 Z71 the other day and it looks like Chevrolet starting putting a vacuum pump on the brake booster in these trucks, not sure when they started it since my 99 NBS Z71 doesn't have one. Thought about snatching one myself and seeing if I can make it work seeing as my 5.3 only makes 7" hg at idle with my Thumpr cam.

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Old 04-22-2012, 06:35 PM   #7
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Re: Help: Not enough vacuum, brakes suck

Interesting. I don't have anything functional to add other than I wouldn't think it was the lack of vacuum ball causing it. I haven't had it hooked up since I did my motor swap and braking is the same with my z06 stuff as before the motor swap.
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Old 04-22-2012, 06:47 PM   #8
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Re: Help: Not enough vacuum, brakes suck

if you motor doesn't produce enough vacuum a ball wont fix it, you'll need a vacuum pump
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Old 04-24-2012, 11:28 PM   #9
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Re: Help: Not enough vacuum, brakes suck

The vacuum ball stores vacuum for the HVAC controls, it does nothing for the booster. The booster itself has a check valve, if it's bad then you'll have this problem.



I have the same problem, car pulls 5-6" at idle and when cruising around. Brakes have no assist unless I ratchet back to 2nd and can build some vacuum. Electric pump or hydroboost is the answer.
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Old 04-25-2012, 08:21 AM   #10
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Re: Help: Not enough vacuum, brakes suck

Quote:
Originally Posted by BlueZee28 View Post
My vacuum is only 11lbs, and should be ~20lbs or something like that.
Quote:
Originally Posted by BlueZee28 View Post
The cam has a lot of overlap too, which makes me think not having a vacuum canister is not a good idea.
11" of idle vacuum is plenty for power brakes. Part throttle cruise would be in the 20's with idle vacuum in this range.
How much overlap do you have? At 59 degrees (on a 110 LSA cam with 276/284 duration) I get 11-12" at idle and the brakes are excellent. LS1 front disc conversion too.
Here's a little test. Run the engine so as to produce whatever vacuum you can. A gauge is helpful (for reference) and a few revs should build more vacuum over the idle value.
At the booster, you should find the previously mentioned check valve.
With the engine off, removing the check valve (and it should be resonably tight) should result in significant amount of air being sucked into the booster. If there is no air transfer, either the booster or the check valve have a leak. That could give the symptoms you describe.
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Last edited by skinny z; 04-26-2012 at 11:02 PM.
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Old 04-25-2012, 09:47 AM   #11
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Re: Help: Not enough vacuum, brakes suck

put the vacum ball back on it Nick
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Old 04-25-2012, 09:00 PM   #12
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Re: Help: Not enough vacuum, brakes suck

Ill test the check valve and booster this weekend, i have a feeling one of them is the culprit.

Cam is a 111LSA...
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Old 04-25-2012, 09:51 PM   #13
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Re: Help: Not enough vacuum, brakes suck

Hydro booster is the way togo for a low vacuum engine.
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Old 04-25-2012, 11:27 PM   #14
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Re: Help: Not enough vacuum, brakes suck

Sorry it took so long to post a pic, had a busy few days, but this is the best pic I could get, it's tucked away under the fender, behind the bumper and out of sight. It's about 8 inches long, about 4 wide. Its by far the best way to get vacuum, chep and easy too. I have a lot of overlap in it and my vacuum is less than 11, but the making more at cruise to hold you over theory didn't work for me. What I found is that you have a ok pedal when you first press on the brake, but it goes away as your stopping because the engine is not replacing the vacuum your using fast enough at idle. Anyway here's a few pics
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File Type: jpg Picture 029.jpg (14.0 KB, 38 views)
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Old 06-22-2012, 10:50 PM   #15
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Re: Help: Not enough vacuum, brakes suck

the vacuum line at the back of my manifold that goes to the brake booster has sucked itself flat. Is that why it's hard to press my brake pedal down? like it stops still but it take a bit of effort and if I really whomp on the brakes I damn near go through the window.
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Old 06-22-2012, 11:02 PM   #16
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Re: Help: Not enough vacuum, brakes suck

That's exactly your problem, replace the vacuum hose and it should be fixed. When the hoses age, they loose there strength and can colapse.
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Old 06-22-2012, 11:05 PM   #17
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Re: Help: Not enough vacuum, brakes suck

sweet deal thanks.
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Old 07-16-2012, 12:32 PM   #18
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Re: Help: Not enough vacuum, brakes suck

I say go for the vacuum pump. I had the same problem when I did my c4 brakes and engine swap, harder than before pedal, brakes don't perform as they do for others with the same setup. My car pulls about 13" at idle when cold, and drops a little bit once warmed up. I installed a vacuum canister from summit racing to help, but I don't think it can hold peak vacuum for very long, and did very little to help. I'll be going the vacuum pump route here shortly myself.

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Old 07-16-2012, 02:37 PM   #19
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Re: Help: Not enough vacuum, brakes suck

I used an electric assist pump from a '04 Silverado. I had to pull it apart to shim the board up a little bit.. it would only pull 7" before, now it pulls 16" or so.


Cheap fix and it works great.
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Old 07-16-2012, 02:37 PM
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