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vacuum leak?

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Old Jun 27, 2005 | 08:35 AM
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Unhappy vacuum leak?

what is the best way to find a vacuum leak on ls1 cars? how would you check the master cylender?Would the car idol funny with a vacuum leak?
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Old Jun 27, 2005 | 10:02 AM
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The extra air would make the car want to idle high, but the PCM tries to "combat" that. You can typically hear the leak sucking.

The question is why? what's your car doing?
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Old Jun 27, 2005 | 10:04 AM
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brake pedal goes down really quickly and feels like no brakes at low rpm, but car doesn't idol any differently.
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Old Jun 27, 2005 | 10:24 AM
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Is the "BRAKE" light on?

A soft pedal with no feel is a problem with the brake system...typically air in the system. Try bleeding the brakes first. Make sure to check for leaks too.
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Old Jun 27, 2005 | 12:06 PM
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no brake light never even opened the master cyl. may try to bleed, but only does at low rpm is what has me trown off.
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Old Jun 27, 2005 | 12:10 PM
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start the car and let it idle for about 30 seconds,then shut it off. 30 seconds later, pull the hose that goes to the brake booster. you should hear a "tsuhh"/whoosh type sound as the vacuum releases from the booster, otherwise, its not holding vacuum for some reason. BTW if the booster wasn't working, you'd have a high/ hard brake pedal.
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Old Jun 27, 2005 | 12:26 PM
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you can press the pedal all the way to the floor and at bottom of travel it will lock the brakes up
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Old Jun 27, 2005 | 01:31 PM
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Definitely not a vaccum leak. There's air in the system, the question is how did it get there. Have you done any work to the brakes lately? Check for leaks, then bleed them.
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Old Jun 27, 2005 | 02:08 PM
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I have had the car since january and the car has never been fooled with to the best of my knowledge. I just changed the oil once and rotated the tires once.and it seems funny that it would just start doing this. anyone else ever had this problem before?

Last edited by pistolpigg; Jun 27, 2005 at 02:41 PM.
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Old Jun 28, 2005 | 11:07 AM
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is there brake fluid in the resevoir. brakes wear down which sends more fluid in the lines, that would cause air but maybe a leak somewhere or just a bad mastercylinder. did you check the pads when you rotated the tires?
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Old Jun 28, 2005 | 12:23 PM
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I looked at pads but only breifly because it has only 40000 miles and I checked the fluid level its at normal. the thing that has me confused is that at idle out of gear the brakes feel good only time they feel krappy is when I leave it in gear and coast down in speed (example 2nd gear to turn)
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