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Thread: Testing for Vacuum Leaks

  1. #1
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    Testing for Vacuum Leaks

    I want to spend so time trying to determine if there are any vacuum leaks on the car.

    Is it possible to pressurize the entire intake, blower, IC, manifold, exhaust systems. Something like making up an adapter with a shrader valve and install in on the MAF then block of the tail pipes and put 40 or so pounds of air pressure on the entire system.

    If anything I would think the header ball flanges would be leaky as hell but everything else should be tight.

    Is there any chance something like this could work???

    HOW THE HECK DID I PUT THIS IN THIS FORUM>>>>>DANG IT!!!!!!!
    Last edited by SCrazy; 11-05-2010 at 10:18 AM.
    Brian Oatway
    '94 SC 2.6KB C4 Auto
    9.956 @ 135.12 mph 1.364 60'
    525rwhp/460rwtq
    "Super Uber Club Member" - per Ira
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  2. #2
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    Move post to Technical.......

    Fraser

  3. #3
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    The best way to test for a vacuum leak is with a smoke machine. If you do use pressure, I do not recommend exceeding 20psi as you may blow out or damage seals etc.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  4. #4
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    Quote Originally Posted by SCrazy View Post
    I want to spend so time trying to determine if there are any vacuum leaks on the car.

    Is it possible to pressurize the entire intake, blower, IC, manifold, exhaust systems. Something like making up an adapter with a shrader valve and install in on the MAF then block of the tail pipes and put 40 or so pounds of air pressure on the entire system.

    If anything I would think the header ball flanges would be leaky as hell but everything else should be tight.

    Is there any chance something like this could work???
    Yes, definitely. I recently tested for and found a vacuum leak on my car with a similar setup. It was pretty easy once I found the right parts and fittings. What I did was to buy a vacuum / pressure hand pump, used for testing HVAC systems. Then I bought a tapered rubber plug of a size that approximately fit the IC tubes and throttle body. The plug had a small hole in the middle. I bought some 1/4" OD copper tubing. It fit nicely through the hole in the plug and made a good seal. At the other end, I used an adapter to mate it to the pump. So then I pumped while holding the plug in place and looked for the leak.

    In my case, I believe I found that it was leaking when I pumped air in at the throttle body. But I still couldn't isolate the spot. So I pulled the blower, plenum, and top IC tube off as a unit. I put the plug in the top port of the intercooler and verified that the intercooler, lower IC tube, return plenum, intake manifold, and valves were all sealing just fine. So I knew the leak had to be in the blower section. With the aid of some vacuum caps for the hard fittings and a buddy to pump while I blocked the IC tube end with my palm, I quickly found that there was a leak at the joint of the blower and inlet plenum.

    I will try to get some part numbers for you later, when I am at home. I do have this ... Here is a listing for the pump I bought. (I got a better deal by finding it used on eBay, but this price still isn't bad.) http://www.patriot-supply.com/produc...item.cfm/46171

    Quote Originally Posted by SCrazy View Post
    HOW THE HECK DID I PUT THIS IN THIS FORUM>>>>>DANG IT!!!!!!!
    Booze for breakfast?
    God bless!!!

    Former Birds:
    1990 SC auto ... red outside, gray cloth inside ... ~225,000 miles ... Sold.
    1990 SC auto ... white outside, gray cloth inside ... ~150,000 miles ... wrecked.
    1989 Base auto ... Crystal Blue metallic outside, dark blue inside ... ~160,000 miles ... Sold.

  5. #5
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    brake cleaner works pretty good to.

  6. #6
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    I made a cap that clamps onto the TB out of a 3" rubber pipe cap (from Home Depot), a large hose clamp, and an old valve stem. If I want to check for leaks, I air up the air compressor (be mindful of pressure - like Dave said), then have someone let air into the gadget and listen/test for leaks. It's real quick, cheap, and works perfect.

    http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053
    Matt Haub
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  7. #7
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    Fastest and easiest way I've found to find to locate a vacuum leak is with a mechanics stethoscope. With the engine running, you can probe the lines and actually hear it. I don't know how well it works for a boost leak, but if I can find a problem 75% of the time that way, I've saved hours of troubleshooting.
    Last edited by TbirdSCFan; 11-05-2010 at 02:35 PM.

  8. #8
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    Quote Originally Posted by slowpoke View Post
    brake cleaner works pretty good to.
    Brake clean doesn't work at all for small leaks because the EEC will compensate faster than you can detect any change in rpm. Many a would-be mechanic has been fooled by this technique. Works for carburetors but not for a modern EFI where the EEC has control of ignition timing.

    Guys, smoke machine. It will tell you in 3 minutes every conceivable leak however minuscule. It's worth the money to have a mechanic test the vehicle and as I said, only takes a couple minutes, no rigging of anything required. Call around and find a mechanic willing to do it for you without charging $100.

    Pressurizing is ok for some things, but you still have to find the leak. If, lets say the bottom of your supercharger inlet was leaking, how would you find that? Smoke machine will tell you in 3 minutes while you drink your coffee, smoke a cigarette, whatever, no disassembly required.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  9. #9
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    Quote Originally Posted by XR7 Dave View Post
    Brake clean doesn't work at all for small leaks because the EEC will compensate faster than you can detect any change in rpm. Many a would-be mechanic has been fooled by this technique. Works for carburetors but not for a modern EFI where the EEC has control of ignition timing.

    Guys, smoke machine. It will tell you in 3 minutes every conceivable leak however minuscule. It's worth the money to have a mechanic test the vehicle and as I said, only takes a couple minutes, no rigging of anything required. Call around and find a mechanic willing to do it for you without charging $100.

    Pressurizing is ok for some things, but you still have to find the leak. If, lets say the bottom of your supercharger inlet was leaking, how would you find that? Smoke machine will tell you in 3 minutes while you drink your coffee, smoke a cigarette, whatever, no disassembly required.
    Do you mean as simple as if you were checking for exhaust leaks?? What would you hook it up to, the TB?

    Ira

  10. #10
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    Pump it in the CAI nipple or one of the vacuum lines on the blower inlet.
    ~Chris
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  11. #11
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    so if i picked up a leftover 500w holloween smoke machine and make up some ghetto adapter to blow the smoke into the intake pipe somewhere before the MAF the smoke with then work its way throughout the system and leak out of the smallest little leak?? Will the smoke machine pressurize the system? Do I need to block off the exhaust?

    Does anybody want to buy a lightly used smoke machine?

    edit: Wow those little smoke machines put out about 2500cfm, I'm sure the fan won't do alot of static pressure but it should force smoke through all kinds of stuff.
    Last edited by SCrazy; 11-05-2010 at 05:59 PM.
    Brian Oatway
    '94 SC 2.6KB C4 Auto
    9.956 @ 135.12 mph 1.364 60'
    525rwhp/460rwtq
    "Super Uber Club Member" - per Ira
    SCCoA Member # 705

  12. #12
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    It will fill the engine with smoke and will leak out visibly from any and all orifices. Definitely don't want 2500cfm, more like 10 cfm if that. It doesn't push out very much smoke at all. It won't simulate boost, but it will find all vacuum leaks, guaranteed. It doesn't create any pressure in the system.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  13. #13
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    Quote Originally Posted by XR7 Dave View Post
    Pressurizing is ok for some things, but you still have to find the leak. If, lets say the bottom of your supercharger inlet was leaking, how would you find that? Smoke machine will tell you in 3 minutes while you drink your coffee, smoke a cigarette, whatever, no disassembly required.
    Funny, that's exactly where my leak was. I knew there was a vacuum leak because of testing with starting fluid ... but it was not at all obvious where it was. It just wasn't precise enough. And the pressure test doesn't show you exactly the leak is ... since air is invisible and all. So that is why I had to remove some parts to isolate the leak. If I had a smoke machine or a knowledgeable / willing mechanic nearby, I guess that would have been more convenient. But it all worked out.

    Dave, you probably know this already, but your PM box was full earlier. To summarize what I was going to PM you, by mail it is.
    God bless!!!

    Former Birds:
    1990 SC auto ... red outside, gray cloth inside ... ~225,000 miles ... Sold.
    1990 SC auto ... white outside, gray cloth inside ... ~150,000 miles ... wrecked.
    1989 Base auto ... Crystal Blue metallic outside, dark blue inside ... ~160,000 miles ... Sold.

  14. #14
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    I went to I-Party this morning and everything Holloween was 1/2 price. I got a fog machine and a gallon of fog juice for $26.

    Gonna see how this goes
    Brian Oatway
    '94 SC 2.6KB C4 Auto
    9.956 @ 135.12 mph 1.364 60'
    525rwhp/460rwtq
    "Super Uber Club Member" - per Ira
    SCCoA Member # 705

  15. #15
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    dumb question...

    when testing for vacuum leaks with a smoke machine, should the car be running or off? i hate that i have to ask this lol
    Last edited by RotaryKlown; 02-03-2011 at 02:45 PM.

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