vacuum leak - Chevy Impala SS Forum
 
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post #1 of 10 (permalink) Old 12-29-2009, 07:49 AM Thread Starter
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Exclamation vacuum leak

What is the best and fastest way to find a vacuum leak on my 1996 impala. It idles at 950 rpm. Rpm jumps around when i shift to drive. Change alot of parts and still no luck. Could it be the brake booster when i press the brake pedal? Oh yeah, when i cut A/c on the idle stick at 1200 rpm then settles at 1000 rpm.
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post #2 of 10 (permalink) Old 12-29-2009, 10:08 AM
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Imho, an unlit propane torch works good for finding vacuum leaks. If you dont find anything with the torch, and you suspect the brake booster, try unplugging the vacuum hose going to it and plugging the hose with something. Crank the car, and see if it still idles funny, but beware as mashing the brake pedal will be a pita while the booster is unhooked.


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post #3 of 10 (permalink) Old 12-29-2009, 01:11 PM Thread Starter
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thanks

i will give it a try,
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post #4 of 10 (permalink) Old 12-29-2009, 01:25 PM
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Here are a couple common vaccum leak areas to look for.
1) The rubber portion of the PCV hose that attaches to the from of the intake under the throttle body.
2) The OTHER rubber end of the PCV tube where it attaches to the PCV valve on the driver's side of the intake manifold. When this one goes, it is usually on the bottom and you cannot see it until removing the line.

See attached pics. Good luck!
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1996 DCM SS, ISSCA #1170

SSled now with ERE#4: 385 stroker with LE3 cam and LE-ported Trick Flow heads.
12.383 @ 109.2 mph, 4350 lbs. race weight at SSHS6 (all motor)
11.895 @ 116.7 mph, 4415 lbs. race weight at SSHS9 (125-shot)
SSHS8 Bracket C Champion
2011 ISSCA Road Race Champion, Race class
2011 ISSCA Autocross Champion, Race class

I drive a hybrid - it burns both gas and rubber.

Waterford Hills Road Course: http://www.youtube.com/watch?v=qXmeEosQLjw
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post #5 of 10 (permalink) Old 12-29-2009, 02:32 PM
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Always a huge potential of leak(s) at the front and rear china walls! The OEM sealant just shrivvels up and disappears after a decade or so.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, SLP SS, 3000 Edge, F/HO bars, METCO extendeds, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear)
\'96FWB BUW-Butt Ugly White: [gonna change that just as I did my last one] boxstock [yep, that's changing too]
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post #6 of 10 (permalink) Old 12-29-2009, 02:56 PM
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Quote:
Originally Posted by 96 Black View Post
Always a huge potential of leak(s) at the front and rear china walls! The OEM sealant just shrivvels up and disappears after a decade or so.
^^^^ He means between the intake and the block.

1996 DCM SS, ISSCA #1170

SSled now with ERE#4: 385 stroker with LE3 cam and LE-ported Trick Flow heads.
12.383 @ 109.2 mph, 4350 lbs. race weight at SSHS6 (all motor)
11.895 @ 116.7 mph, 4415 lbs. race weight at SSHS9 (125-shot)
SSHS8 Bracket C Champion
2011 ISSCA Road Race Champion, Race class
2011 ISSCA Autocross Champion, Race class

I drive a hybrid - it burns both gas and rubber.

Waterford Hills Road Course: http://www.youtube.com/watch?v=qXmeEosQLjw
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post #7 of 10 (permalink) Old 12-29-2009, 08:53 PM
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I use water with a couple of drops of dishwashing liquid. Spray it on the vacuum lines, and it will suck it up if there is a leak. The dishwashing liquid is to break the surface tension of the water. It is a lot safer than propane floating around the engine compartment.

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For a parts list, check http://www.impalassforum.com/vBullet...1#post11691762
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post #8 of 10 (permalink) Old 12-30-2009, 01:35 AM Thread Starter
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thanks for the info

I will check this out this weekend.
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post #9 of 10 (permalink) Old 01-03-2010, 09:39 AM
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Quote:
Originally Posted by LeadSSled View Post
^^^^ He means between the intake and the block.
Correctomundo.

Ssssooooooo, weekend's almost over. You pop that intake yet? ::Wink::
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\'96SS SOB: SSRI, Herter Tune, Tri-Y II, SLP SS, 3000 Edge, F/HO bars, METCO extendeds, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear)
\'96FWB BUW-Butt Ugly White: [gonna change that just as I did my last one] boxstock [yep, that's changing too]

Last edited by 96 Black; 01-03-2010 at 09:44 AM. Reason: Jus' givin' a brother some S**I
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post #10 of 10 (permalink) Old 01-04-2010, 12:30 AM Thread Starter
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engine rebuilt last summer

I had my engine rebuilt and weaker than before. the mechanic says its running lean on the dyno 13.5-15 WOT. I had my pcm programmed by Bryan Herter before and checked afterwards. Bryan says it a vacuum leak. I looked all over this engine and cant find nothing yet.I did not get a chance to try any of your response yet.I'm waiting on my service manual to come this week.
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