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Old 04-14-2011, 04:21 PM
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Finding vacuum leak.

Can anyone tell me the best way to find a vacuum leak on the intake manifold or carb. This is a stock 350 Chevy. Also is it possible for the master cylinder to leak fluid into the vacuum booster and then be sucked into the intake through the vacuum line? Thanks.

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Old 04-14-2011, 04:28 PM
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Quote:
Originally Posted by rustman
Can anyone tell me the best way to find a vacuum leak on the intake manifold or carb. This is a stock 350 Chevy. Also is it possible for the master cylinder to leak fluid into the vacuum booster and then be sucked into the intake through the vacuum line? Thanks.
Take a can of carb cleaner and spray around different areas. Some use a propane torch, just don't light it open the valve so a little propane can come out, and hold it close to intake gaskets, vacuum lines and things. Carb cleaner with the straw on the tip works well too. If you spray a spot and the engine revs up a little, then you've found the leak. I myself use carb cleaner over propane anytime it's alway's worked best for me. JMO

Cole
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Old 04-14-2011, 06:27 PM
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Finding vacuum leak

Thank you Cole. Will give it a try.
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Old 04-14-2011, 06:45 PM
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boosters can get fluid in them. I had one half full. It didnt work well.
I use a piece of hose to find vac leaks. Put one end in your ear and probe with the other end. The method cole mentioned works also.
I put a short piece of metal brake line in the end of the hose to probe around for exhaust leaks. works well if you are in a noisy shop. it is real good for getting to those manifold leaks, and pinpointing .
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Old 04-14-2011, 06:50 PM
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I totally missed the part about the booster sometimes the M/C will bypass into the booster if the fluid get's in there it can ruin the booster.JMO


Cole
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Old 04-14-2011, 07:01 PM
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I have tried a lot of methods, including spraying combustible aerosols like carb clean. I still do use the carb clean but it can drift and cause the diagnosis to be more difficult. The method I like best is my stethoscope with the hose open on it. You can pinpoint the smallest vacuum leak exactly to the source that way. You can do the same thing with a section of vacuum hose and just listen in the end of it as you probe around the suspected area with the other end.
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Old 04-15-2011, 03:25 PM
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