Brake booster vacuum woes....please help?!?!

[distel]

73 DART SWINGER SLANT AUTO. I decided to put in one of those power brake upgrade kits, booster, master and bracket. I used the port on the intake manifold for my vacuum source but now it runs like crap when I step on the brakes. All the connections are good and I double checked the booster check valve and booster for leaks with the mighty vac and it holds??? What's a good source for vacuum? Or maybe a vacuum reservoir canister? Stock engine cam as far as I know.....Any advice is greatly appreciated.
Thanks
Eric

 

[distel]

Oh and it's stock disc in front and drum in rear, don't think it matters though?

 

[GTS Dave]

Oh and it's stock disc in front and drum in rear, don't think it matters though?

I saw an episode of GYC that addressed this very issue. Adding the vacuum reservoir canister fixed it. Need to test your vacuum pressure to be sure.

 

[67Dart273]

If it "runs like crap" when you step on the brakes then you have a vacuum leak "somewhere" might be the booster itself

 

[TrailBeast]

If it "runs like crap" when you step on the brakes then you have a vacuum leak "somewhere" might be the booster itself

Yea if it runs like crap the entire time the brakes are being held.
It's actually common for the engine to stutter a bit on the apply but it should smooth out again after the diaphragm stops moving.

 

[distel]

So I replaced all the vacuum lines and tested the booster with the mighty vac, it held a vacuum? So then i hooked up to the reservoir for the hvac system and saw a real improvement! Ordered a bigger aftermarket vacuum reservoir for cam modified engines, hopefully that will be the fix?

 

[pishta]

The reservoir on my moms Lincoln looked just like a 3lb coffee can.

The booster may be leaking internally if its killing your idle when your depressing the brake, try this:
"....Test the booster
Since most vehicles use a vacuum system, the brake booster can be tested at your home. With the engine off, pump the brakes several times, about five or six times is sufficient. This depletes the stores vacuum. Turn the engine on while pushing down lightly on the brake pedal. If your brake booster is working normally, the pedal will fall away a little bit but then become firm. If your brake booster is not working correctly, then nothing will happen, or the brake pedal will push back against your foot, once the engine starts. This could be a sign of a brake booster problem or an issue with the vacuum hose..."

 

[TrailBeast]

The reservoir on my moms Lincoln looked just like a 3lb coffee can.

The booster may be leaking internally if its killing your idle when your depressing the brake, try this:
"....Test the booster
Since most vehicles use a vacuum system, the brake booster can be tested at your home. With the engine off, pump the brakes several times, about five or six times is sufficient. This depletes the stores vacuum. Turn the engine on while pushing down lightly on the brake pedal. If your brake booster is working normally, the pedal will fall away a little bit but then become firm. If your brake booster is not working correctly, then nothing will happen, or the brake pedal will push back against your foot, once the engine starts. This could be a sign of a brake booster problem or an issue with the vacuum hose..."

My MK4 had one like that and I think it was a restaurant supply 1 gallon bean can.
Or maybe hominy, or spaghetti sauce who knows.

 

[GTS Dave]

This is a link about the GYC brake vacuum issue I mentioned, from the B body forum.

Power Brakes Vac Pump

 

[RedFish]

The slant 6s with EGR have a vacuum amplifier. Those are 3 port and 4 port types. I don't know enough about those, their differences, if you have or not, how adding a brake booster might effect any of that. Knowing EGR operation also drastically effects engine idle like any other vacuum loss has me mentioning here. Good luck with it.

 

[distel]

The slant 6s with EGR have a vacuum amplifier. Those are 3 port and 4 port types. I don't know enough about those, their differences, if you have or not, how adding a brake booster might effect any of that. Knowing EGR operation also drastically effects engine idle like any other vacuum loss has me mentioning here. Good luck with it.

I do have some of the EGR components install on the car but not in use, the vacuum switch on the fire wall and that thing below the carb by the exhaust manifold, both not in use. However I do not have the puck shaped vacuum amplifier on the valve cover? I'm hoping the reservoir will be the fix???? Forgive my naivety but can I use my mighty vac hand pump to test how much vacuum the engine is producing?

 

[halifaxhops]

Yes you can just hook it up and read it.

 

[distel]

Yes you can just hook it up and read it.

Where the best location to read from?

 

[halifaxhops]

Manifold vacuum if you can, definitely not where the vac advance hooks up to. I have a can and a vac pump but have a huge cam, there is just something going on with yours that you have to figure out. The cars with a vac reservoir usually have a lot of vac controlled devices like headlight doors etc.

 

[halifaxhops]

Anything over 15" and you should be good for a booster than have to find what is going on then.

 

[distel]

I don't know much about engine vacuum, I replaced all of the vacuum lines, capped unused ports on the carb, sprayed carb cleaner to check for leaks (but I could have easily missed something when I did the spray test, wasn't comfortable spraying a flammable liquid around!)

Must be something inside the engine, rings... intake manifold gasket, exhaust? I have no clue? But using the small stock reservoir worked well but not perfect.

 

[halifaxhops]

CHECK THE VACUUM AND SEE WHAT IT IS BEFORE GOING THERE.

 

[halifaxhops]

Just read back missed it was a slant, on one of the intake runners you should have a plug with at least one vac nipple on it ideal place to hook the gauge up to.

 

[distel]

I'll check the vacuum on the engine and report back, thanks for all of the help so far!

 

[MoparLeo]

Use a spray bottle with water next time to check for vacuum leaks. All that this is doing is finding a change in rpm's. Water will cause a decrease or stumble and won't cause a fire. Any time you are under the hood it is a good idea to have an extinguisher handy. I hope you have one in your garage. Cheaper than insurance. You are right about it not being a good idea to spray flammable liquids on your engine when it is running. But you would be amazed at how many "mechanics" do it.

 

[distel]

Use a spray bottle with water next time to check for vacuum leaks. All that this is doing is finding a change in rpm's. Water will cause a decrease or stumble and won't cause a fire. Any time you are under the hood it is a good idea to have an extinguisher handy. I hope you have one in your garage. Cheaper than insurance. You are right about it not being a good idea to spray flammable liquids on your engine when it is running. But you would be amazed at how many "mechanics" do it.

I've heard of using water before but was warned away from it because of possible engine damage. hydrolocking or something?

 

[AJ/FormS]

Does the 73 carb not have a booster tap on it? I hate pulling vacuum for the booster off just one leg of the intake. That particular cylinder will go slightly lean on every application.
But really your booster has a problem in the control valve , I think your engine is sucking straight thru it, whenever the pedal is applied. That ain't right. It's broke or assembled wrong. The auxiliary canister won't help.
I had a neighbor once who installed a brand new booster and didn't check the pushrod length. He broke the control valve the first time he stepped a lil hard on the pedal. That sucked,lol.

 

[halifaxhops]

Does the 73 carb not have a booster tap on it? I hate pulling vacuum for the booster off just one leg of the intake. That particular cylinder will go slightly lean on every application.
But really your booster has a problem in the control valve , I think your engine is sucking straight thru it, whenever the pedal is applied. That ain't right. It's broke or assembled wrong. The auxiliary canister won't help.
I had a neighbor once who installed a brand new booster and didn't check the pushrod length. He broke the control valve the first time he stepped a lil hard on the pedal. That sucked,lol.

Totally agree just to check the vacuum there to see what it is.

 

[BillGrissom]

The brake booster does leak. That is how it works. When you push the pedal, its control valve leaks atmospheric air into the aft side of the diaphragm, which gives the assist force. But, at that point the engine should not be affected. If it is, something is wrong with the control valve or the diaphragm has a tear. When you release the pedal, the outside air is blocked off and the leaked-in air is then sucked into the intake manifold, so if working correctly it is on pedal release that would would feel the engine affected. I never tried any of this, just thinking it thru (I might be wrong). Anyway, I have never felt the engine affected in any of my power-boost vehicles so it seems your booster has a problem.

 

[distel]

So I finally got the setup working fairly well. Replaced the booster and the kit manufacturer suggested that I raise the position of the bracket. I was only able to move it 1/4 of an inch but that did the trick. There still is a vacuum issue but I tested it at the manifold with two different gauges. The mightyvac hand pump gauge readings were bouncing everywhere. But the other gauge read at 19 with a very minuscule vibration on the needle. Dropped it off at a shop today for them to check the timing, vacuum and carb settings. Thanks For everyones advice and time.