'94 TBird w/o ABS brake NEW booster not working

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Old 08-04-10, 01:28 PM
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'94 TBird w/o ABS brake NEW booster not working

1994 TBird LX 3.8L non-ABS standard brake system.....Replaced the booster thinking this would fix a percieved vacume leak. Ordered the new one thru Adv Auto and changed them out. Wigglin that sucker out/in to the kimited space provided turned out to be a bear.

Anyway now there is NO power boost whatsoever. I have to really crank on the pedal to get it to stop. Reminds me of some old cars I used to dirve as a kid. Scary at first, but I've gotten used to it and have recent;y drove it to Ohio and back to Virginia with no problems. Though i wouldn't let anyone esle use it for now.

I checked the vacume where it connects to the boost can and it seems strong. Small electrical connector to the master cylinder is clean and connected. The previous booster had an air leak sound on the inside under the dash. A little squishy too and the brakes pulled ot the left if you got on them hard. There is no such sound now and no pulling. But at least the old worked or was assisted. The pedal is not squishy. It's pretty solid with not a whole lot of travel really. Don't think I could lock'em up if I tried with both feet on the pedal.

I bled the entire system a couple of times over as well since I had to disconnect the master in order to work the booster can in/out. The rest of the brake system was replaced a year ago due to rusty lines and one sprung a leak.

This car only has 77k original miles on it and is in great shape (except this and the driver seat motor is giving me fits, that's another post). Could it be the part itself is faulty, or no I've done something to the internal diaphram or other self-inflicted wound?
 
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Old 08-05-10, 05:03 PM
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You have a good vac supply...... Did you pull the check valve out of the booster to check vacuum, or just pulled the hose off????

Get in the car. Put the keys in your lap. Pump the brake pedal 15 times, then hold it down as firmly as you can---(Even if you have to stand on it). While holding the brake down, start the car. It should sink about 1.5 to 2 inches when the motor starts. If it doesnt, it isnt working.

If you have sufficient vacuum "THRU" the check valve...then your new booster may be deemed.. "N.F.G.".
 
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Old 08-06-10, 02:38 PM
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Just pulled the hose off to check vacume.

I will try the pumping trick. Right now it feels no different with motor running than it does sitting off. I now have logged over 1200 miles like this. Right after I changed it out, I went on a roundtrip to visit family for a week. I done pumped it every which way but loose, but haven't attempted prior to start though i feel it will show no results. I will let you know.
 
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Old 08-06-10, 03:33 PM
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Pop the check valve out, and make sure the vacuum makes its way thru the valve.

***** You did remember to take the plastic cap off of the check valve before putting the hose on ...Didnt You???****
 
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Old 08-10-10, 09:05 AM
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Did the pumping then start trick with no new results.

There did not appear to be a cap on the check valve. Myself and a couple others have pulled that hose off to check vacume while standing there discussing over a beer. Unless it's a plug typed versus a cap over type and it's not noticed? I'll sanity check it just make sure, including popping the check valve completely out and check vacume. It won't hurt anything popping that valve out will it? If all fails my plan is to simply order another thru Advance and return mine as a non-working part and exchange it.

The only other thing I can think of is when installing I had to compress the brake pedal actuator rod piston inward in order to allow room to wiggle the can into mounting position. I then clamped a set of vice grips on the opposite end rod that enters the master cylinder to hold it. Once while attempting this by placing the pedal rod against the ground and pushing downward on the can to compress the actuator, it slipped sideways on me. Could it be possible that could have damaged an internal diaphram or something? There is no noise or hissing sounds from leaking vacume like there was prior to changing. Not sure what the guts are like in one of those.
 
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Old 08-10-10, 04:12 PM
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Cap----.. actually refers to a small "Insert" stuck in the Check valve inlet to prevent dust and moisture intrusion during shipping. Its a tiny little thing, maybe 3/8 of an inch long, just stuffed into the check valve inlet.

Removing the check valve for test purposes wont hurt anything. Wiggle it a bit while pulling out....It will pop free. A little spit, and push it back in to replace it.

Now ...hold the valve up to your face, with the booster side of the valve toward you. Suck on it, it should be free -flowing. Next, blow into it. it should be blocked . flip it around so engine side is facing you, and the results should reverse. That is designed that way to prevent a Backfire from blowing the booster apart.

If it doesnt pass the "Suck-N-Blow " test, try the valve off your old booster.
I doubt you hurt it, Because if you did, Either the brakes wouldnt work, or it would be hissing away. You have described classic "No VAC SUPPLY" symptoms, Or the booster is "NFG"
 
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Old 08-11-10, 11:23 AM
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Now that makes the most sense. If it's the insert/plug type not overtly visible, then no I would not have noticed or expected a plug to remove. I was consumed with getting the thing wiggled into place etc as explained above and did not look for or notice one. That would be funny if that was the problem after having driven it to Ohio and back and ever since with no boost assist. I was prepared to swap out with another. BTW the old one got turned in already for the core rebate.
 
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Old 08-11-10, 12:19 PM
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Sorry....The Suck n Blow test is backwards.......

If you need a new Check valve, most parts stores will have SOMETHING that will replace yours.
 
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Old 08-11-10, 01:42 PM
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Good to know. Hopefully when I get home tonight and pop off the vacume line, I'll find a plug in there and fix the problem.
 
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Old 08-12-10, 06:52 AM
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Well I checked the valve and there was no plug and te valve worked just fine after doing the test on it. Good strong vacume from the line. Guess the booster has to be crap.
 
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Old 08-12-10, 12:27 PM
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(Quote) Guess the booster has to be crap.


Maybe, but before you throw the booster under the bus make sure there isn't a vacuum leak at the grommet that the valve fits into.
 
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Old 08-16-10, 11:12 AM
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I will check one more time. The booster was brand new or rebuilt? out of the box. The valve was already in place. I just hooked the hose up to it. It also took a bit of wiggling to work it out and test the other day.

What would be nice is to see a diagram of the internal workings to see if maybe I did something to it trying to push the plunger in and vice-gripped to install?
 
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Old 08-16-10, 01:13 PM
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Only three possibilities are left.

1. Wrong booster.
2. Master wasn't bench bled prior to re-installation.
3. Although you claim bleeding the system was done:

Are you aware that bleeding must take place at all four wheels?

Are you aware that there's a specific order to "Brake Bleeding"?

Were you able to break open all four bleeders without damage or breakage?

Did you try "Power Bleeding"?

Are you really sure there isn't still air in those lines?
 
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Old 08-16-10, 05:27 PM
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Gotta disagree on this one.....

Typically , airbound, or Bleeding issues would show as spongy or sinking pedal....But yet There is no reaction from the booster when the engine is started, and vacuum applied. If this were an air issue, I would think the brakes wouldnt function adequately to stop the car , whether or not there was power assistance or not.

Think of this as two seperate Animals...BRAKES, and Power assist. Inside That can is a rubber diaphragm centered between the two halves. On the master cylinder side of the Diaphragm is a spring that holds the diaphragm at center. The spring goes from the diaphragm to the inside of the Outer case half. When you apply vacuum, the diaphragm is sucked toward the master cylinder, but is stopped by the spring. Stepping on the brake pedal at this point, Is merely to overcome spring pressure and allow the diaphragm to be sucked forward.At that point, your brakes are being applied, primarily, by the vacuum that sucks the diaphragm forward, and not by your foot.

Damaging it during installation.... Would either, Break the spring, in which case , the brakes would be locked at all times, or Damage to the pushrod Bore, in which case, the brakes would not activate at all.
 
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Old 08-17-10, 07:19 AM
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Yes I followed the manual's instructions on bleeding all four locations starting with the right rear. Actually did it twice.

Grommet was good tight BTW.

At this point I'm pretty convinced either I messed it up as described above, or it was definitely a defective part.

To top it all off, the left front lower ball joint sheared off on me last night turning into a parking lot. Heard a sudden poiw and the wheel was all cockeyed in the wheel well. AAA and a six hourt wait/evolution later she's in the shop.
 
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Old 08-17-10, 11:16 AM
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Advance could have sold you a defective booster. My gut is telling me it's the "Wrong" booster. (Rod issue)
 
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Old 08-18-10, 01:44 PM
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I spoke with them today. They will take it back for an exchange or refund whichever I choose. I'll make sure they are specifically providing me with the right one next go around. I hate having to do it agian. It was a PIA working that thing out and especially back in. Then having to bleed the system. Arrrrg!
 
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Old 08-18-10, 02:14 PM
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Next time around.....

Leave the lines attatched to the master cylinder, and just push it as far back as you can. There is more than enough "Flex" in the lines to move it out of the way without opening the hydro system.
 
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Old 08-19-10, 01:55 PM
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I tried and tried the first time with no real room to wiggle. I'll try again without kinking or bening the lines. I needed every little inch last time to get out and squeeze back in.
 
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Old 08-19-10, 02:19 PM
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Boater59,

You realize when you finally resolve this isuue, that you will have to buy us all a "Few Rounds of Drinks"?.Beer 4U2
 
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Old 08-19-10, 04:33 PM
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  1. Disconnect battery ground cable and remove air cleaner. Pump brake pedal several times to exhaust any vacuum in the booster.
  2. Disconnect manifold vacuum hose from booster check valve.
  3. Disconnect brake lines from primary and secondary outlet ports of master cylinder.
  4. Remove master cylinder to booster attaching nuts and the master cylinder.
  5. Remove windshield wiper motor.
  6. Working under instrument panel, disconnect electrical connector from stop lamp switch.
  7. Remove hairpin type retainer. Slide stop lamp switch off brake pedal pin just far enough for the switch outer hole to clear the pin, then lower switch away from pin.
  8. Remove booster-to-dash panel attaching nuts.
  9. Slide booster pushrod, bushing and inner nylon washer off brake pedal pin.
  10. Move booster forward in engine compartment until booster studs clear dash panel, then rotate front of booster toward engine and remove booster.
  11. Reverse procedure to install, noting the following:
  •  
    1. Ensure proper clearance between pushrod and master cylinder exists.
    2. Bleed brakeHydraulic system.
    3. Torque booster-to-dash panel retaining nuts to 19-25 ft lb.
    4. Torque master cylinder-to-booster locking nuts to 16-25 ft lb.
The "Coils" in the brake lines should be enough to permit lifting the whole M/C assembly back and "UP" out of your way, so you may eliminate step 3. Pay special attention to step 5. This is the key to eliminating frustration.
 
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Old 08-19-10, 06:20 PM
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Booster

Reading that just refreshes my memory as to why I put the snap ons in storage.
 
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Old 08-26-10, 11:08 AM
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Thanks guys for the step by step and advice. I have the repair manual which states pretty much the same thing and yes I followed. I replaced the booster this past Saturday. Second go around actually went a lot better though still aggravating. Wiggled the booster in position fine with lines disconnected.

The hard part was aligning the booster mount bolts with the holes in the firewall. Reason being the metal brake pedal bracket under the dash slid away just enought to require a little bottle jack action to get it re-aligned. Totally bled out the lines a gain, and voila! got brake boost once again.

Took the first booster back to A Auto for a refund. Thanks again for your patience and sound advice.
 
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