The check valve and grommet were in the new booster when I got it and were never touched so I am pretty sure they are good and like you said the vacuum dropped immediately when I unclamped meaning the booster was already empty. I plan on changing the booster as soon as it gets here so I will post a follow up when I get it on, hopefully before Christmas.

 

Was your vacuum gauge between the check valve and the booster? If not, this test was bogus.
If so, you probably only need a new check valve, rather than a whole new booster.

 

My first thought as well, but The check valve should be before the vacuum canister, or it wouldn't help with a low vacuum condition.

 

Gauge is mounted on top of the vacuum canister, line goes from plenum to canister, from canister to booster. I clamped the line from canister to booster after the gauge.

 

So there is a check valve between the canister and plenum, right?
Also - where did you get your canister? I am thinking of putting one on mine, since my vacuum is a little lower than normal, but I would like to find something that is not too expensive.

 

The check valve is in the booster and there is also one in the canister. I got the canister off ebay, this is the item number for one just like it from the same seller. 360799052773

 

The bias spring just changes the crack point (pressure) or when the rear brakes starts to come into effect (action). It would not affect front brake lines unless the valve was not centered correctly perhaps.


Got my 94 in 03 and had poor brakes. Had to stand on them and leave lots of extra room in front of me (scary) Over the course of time I changed almost everything. Pads, rotors, flex lines, caliper rebuild, ABS unit and master cylinder. Made no real improvement with all that effort. Booster worked fine with no signs of any leakage.

I got a J55 brake setup with calipers, rotors and pads you could not find at least on the east coast. Whatever the combination was it worked great. So well I had to install the DRM bias spring to avoid the noise from diving which worked fine.

When it was time to replace pads I had a similar problem where stopping was not as good as it was for the past few years. Was not until I found Brembo pads I got good braking again.

Fast forward a few years my original booster finally went bad. It had the classic leaking vacuum problem with a routine replacement needed. So I did nothing fancy or upscale and just went to AutoZone and got a booster. Installed it and when I drove the car the braking performance was just greatly improved. I can't explain it or have any real good high tech answer for it. I just now had to touch the pedal and got real good stopping power with a lighter touch (had to re-calibrate my foot). Braking was as good as any new car.

Many have tried to fix their braking problems as I and have replaced the booster with no improvement. I'm just glad it helped me and to have a safer car.

Don’t know if this will directly answer any questions but might give you something else to think about from my experience.

 

Thanks for the info. Once I looked at the canister, I decided I would try to find a neat looking container and make one myself - would make a good conversation piece. (plus i'm just cheap like that, lol.)

 

There is no better information than that which is gained by personal experience. Your thread could help me or any other member and also make their car safer. I had a close one last summer, approaching an intersection on a 4 lane city street separated by a median. I had the right of way when a blue hair who was coming from the opposite direction turned right in front of me. A guy next to me put his car sideways in the intersection and I was able to avoid her but I really don't know how. I'd bet the thickness of my hand would not have fit between my right front & her right rear as I managed to avoid her. If I had had good stopping power it may have made a difference but I made myself a promise that day that I would not take another trip until the car was right.

 

UPDATE:
As I said, I will post what I find and the outcome. The "new" brake booster was built apparently by a gorilla. The plastic case is held together with two bolts, these bolts go through plastic tubes which are made right into one half of the case and have o rings for sealing the other half. The gorilla tightened the bolts so tight it snapped off one of the tubes which allowed the case to separate slightly and move the rubber diaphragm out of place. I had taken the booster off the car and hooked my Mityvac to it. It would only pump up to two inches of vacuum & lose it immediately. This is when I took it apart & found the broken piece. My new STEEL booster will be here tomorrow but I am not sure when I will get it on but I will post those results asap.