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Old 07-11-2007, 12:54 PM
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Location: North of Pittsburgh, PA
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Is my brake booster bad? 82 300DT

I have an '82 300D turbo. I just replaced rear brake hoses, rotors, calipers, and pads. Everything up front was fine (car had been sitting for some time and the rear brake stuff was badly rusted). I had no assist before the job or after. Thought vacuum leak. Everything vacuum related works, car shuts off, door locks fine, etc. I went through the system anyway and could find no obvious leaks. Everything bled wondefully and went together like a charm. Mechanically and hydrolically everything is as it should be. Plenty of pedal and they all grab the way they should. Problem: no assist and no stop without putting the pedal to the floor. When I pulled the vac line to the booster it held my finger fast at idle. How much vac pressure should be there and is my booster bad?????

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Old 07-11-2007, 12:58 PM
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Quote:
Originally Posted by dbn1066 View Post
Mechanically and hydrolically everything is as it should be. Plenty of pedal and they all grab the way they should. Problem: no assist and no stop without putting the pedal to the floor.
No assist is one thing; no stop is another. If the pedal is going to the floor, things are not as they should be.
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Old 07-11-2007, 01:04 PM
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sorry for the confusion, just using "to the floor" as a figure of speech. I know better. The pedal goes down and stops well before the floor. I have good pedal, just no assist.
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Old 07-11-2007, 01:12 PM
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If you other vacuum items work okay, you have enough vacuum to operate the booster. Aside from an internal booster failure, about the only likely culprit is the seal between the booster and master cylinder.
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Old 07-11-2007, 02:38 PM
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I've heard of someone testing this by hooking up a hose to the booster after you've removed the one from the vac pump, with a series of adapters, and using a mighty vac, pump, pump, pump...etc till you get a reading and will hold vacuum. If you can't get much after many, many, many pumps, you may need a different booster.
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Old 07-11-2007, 08:17 PM
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Might check the thickness of the rotors. If they are too thin, it doesn't matter how good everything else is. The calipers only push the break pads in so far. If the rotors are too thin they pads won't catch enough to stop you like they should.

Checking your booster. Hook you mity vac up to the main vac line. If you have two ports comming off the main vac line plug the second one. Start the car. You should have 20-23" Hg. If you do then your break booster and vac pump are fine. If not then use a wrench to remove the main vac line from the break booster. With the car still running plug the end of the vac line you just removed, and read the mity vac. If the vac gauge reads 20-23" your booster is leaking. If is stays the same your vac pump is bad.

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