Vacuum brakes changing BL #'s???????

[2QWIK4U]

I've been having a couple of problems and I'm beginning to think one is causing the other.Since switching my car over to vacuum brakes I've not been able to hold boost at the line,before the old powermaster went out I never had this problem.Sometimes I hit the brakes and the pedal feels fine then it slowly gets very hard.The next time I hit it the pedal is hard as a rock to begin with.I've bled them over and over.I'm almost certain now that I've got a bad booster.I don't have a vacuum block that came on the TTA so I just spliced into the PCV line.Could this be the wrong place to do so until I get a TTA vacuum block?
The other problem is my bl #'s going to 155-160 upon even light acceleration,I've had my JL chip reburned over and over,also spent all day checking for vacuum leaks but didn't find any.
Set fp to 42lbs today (line off) and bl's wanted to stay around 141-145 at idle.Out of curiousity removed vacuum line from booster and plugged it and bl's went to 127-129!!!!
Has anyone had these problems after switching to vacuum brakes?Is the booster bad or should I go back to a powermaster?
Thanks in advance for the help!!!

 

[TurboDave]

Sounds very much like a bad booster!! It doesn't take much of a vacuum leak to drive the BLM's up sky high, especially at idle.
Removing the booster from the vacuum circuit and watching the BLM's drop to normal pretty much proves there's a problem out there in the booster someplace (internal vacuum leaks).

 

[Chuck Leeper]

Hard pedal

When the vac goes to zero at the starting line [when boost is coming on], the PVC closes, the boost then goes against the vac. booster check valve.The valve won't hold off the boost PSI, [which it's not designed to do,[if it's N/A valve] only retain some vac. in the booster], the diaphram gets a blast of boost, the vac. is obviously gone at this point , and the brakes become hard. Enuf of this and the boost diaphram is leaking, possibly coated w/ oil mist from the pvc, and rotted.

Not a good thing!! The PM wouldn't do that as it has no vac. source from the engine.

 

[Steve Wood]

Normally, there is no problem with the check valve holding against boost...

be sure the check valve is working and the booster is holding vacuum. Sounds like one or the other is not good.

 

[2QWIK4U]

So will a vac. booster setup ever be able to hold the same amount of boost the PM did?Because at the redlights at 1-2 psi it starts pushing through,sounds like I may need to go to Auto Zone and buy a PM.I've held 7-8 psi easily with it!

 

[Steve Wood]

I can hold 10# with no problem.

 

[2QWIK4U]

Thanks Steve.I installed a new check valve when I swapped it over . I'll try another one since they are cheap,then I'll see what happens.

 

[Steve Wood]

easy way to tell if check valve is working is to crank it up and then kill the engine a few seconds later. Then pull the check valve out of the booster. If you hear a hiss, then the booster was holding vacuum.

My cars actually stop better with vacuum but I have seen others that stopped very well with the PM...mine never did.

I had to pull my larger rear cylinders off after swapping to the brass proportioning valve as I suddenly had too much on the rear and it was difficult to stop without spinning out on a wet road.

Be sure the brakes are well bled ( I use the gravity method) and the rear shoes are adjusted properly.

 

[2QWIK4U]

I pulled the check valve today and it did hiss...where did you connect to pull vacuum for the booster?
Even though it had the hissing sound is there any way to tell if maybe the booster has a small internal leak?

 

[Steve Wood]

I use the vacuum block with the additional brake port on it-copied after the tTA unit.

I guess it you wait a couple of minutes, it should still hiss the same....otherwise, if leaking, it would go down very fast.

 

[2QWIK4U]

Is the booster check valve on the TTA's different than the normally aspirated vehicles?Are they designed differently to withstand boost pressure?
Anyone have a part#?

 

[Roger]

I tried the vacuum brakes.
After thefourth unit leaked, I gave up.
Discoutn AutoParts, lifetime warranty PM $199.

 

[Orion231]

Question...

I have vaccum brakes that my dad ghetto rigged from the junkyard... He did an ok job so now that I have the car I am wondering if he connected them correctly... He ran the vaccum tap to the PCV line, with only an inline oil filter no check valve or anything. So I bought the TTA billet Vaccum block, and installe dit and ran the line with a new filter on it. Am I supposed to have a check valve on this? I do not have one, just a oil filter. My vaccum ball under the drivers sidefender works fin it holds vaccum. Can I take apart my vaccum canister and clean all th eoil out of it and then put it back in? How do I do that? And what check vavle am I supposed to use?

 

[John Larkin]

ghetto rigged, hahaha; that made me laugh. The check valve is the 90 degree fitting that goes from the vacuum line and goes into the booster. It's a round shaped cylindrical plastic valve about 1/2" thick with a 3/8"-ish barb on the side and one out the backside. The vacuum line goes into the side barb and the backside barb plugs into the booster. You can blow through it for a quickie check to see if it's working properly. A new one is available on the HELP! cards at the parts store for under $2.00.

 

[Orion231]

I have one...

Ok that is the one I have I bought a new one from the Help Section at Checker... A Quick question. Mine has a straight barb and the othe ris a 90* angle....which one goes where? I guess I cna pull it off and go blow in it...lol. Also, how do we tap into the vaccum booster ball? Is the vaccum system plummed into it for the brakes.... Can we make a reserve for vaccum brakes?

 

[Steve Wood]

Normally, it is a 90 deg piece that plugs into the vacuum booster.

You do NOT tap into the vacuum ball. You can either tee into the pcv line or buy a new vacuum block from most vendors that has a large vacuum port on the driver's side just like the TTA model has.

 

[2QWIK4U]

Ordered TTA vacuum block today