vacumm leaks?

[jesse0880]

is there a fool proof way ( easier) way to check for vacum leaks, and leaks before the throttle plate for that matter? i was told they have smog machines were u can hook it up and if u have a leak, u can see the white smoke come out. has anyone ever heard of this?

[430hpToy]

yea, it's a smoke machine that burns oil (babyoil) and produces smoke. you pull a vacuum line and plug the smoke machine to that. if it's turbo charged you'll have to block the compressor side of the turbo. otherwise all the smoke will come out at that point.

there should be a local mechanic in your area that has one.

[tHa kNiGHt FaLL]

a 20.00 vacuum gauge will tell you if you have a leak... or even a boost gauge if you have a turbo. if your not reading vacuum... say around 17-22 inches or so at idle then you have a leak. a vacuum leak before the throttle plate you won't notice a vacuum leak thru the gauge but you will notice a severe performance lost as un metered air enters your intake.

[jesse0880]

17-22 inches eh? my boost gauge reads about 12-14.

[tHa kNiGHt FaLL]

Originally Posted by jesse0880

17-22 inches eh? my boost gauge reads about 12-14.

12-14 at idle...?

or under some kinda load...?

that is incredibly low and its surprising the motor wil stay running.

[jesse0880]

at idle. when im driving its about 15-16 until i give it throttle, then it levels off at zero until boost begins to build.... but i definitly have a performance problem. the motor runs great until about 5k or about 7-8 psi. what i dont get is the spring in my ext. wastegate is manufactured rated for 10 psi.

[tHa kNiGHt FaLL]

Originally Posted by jesse0880

at idle. when im driving its about 15-16 until i give it throttle, then it levels off at zero until boost begins to build.... but i definitly have a performance problem. the motor runs great until about 5k or about 7-8 psi. what i dont get is the spring in my ext. wastegate is manufactured rated for 10 psi.

ok. now remove the inlet from the turbo to the throttle body. w/ the engine at idle put a flat piece of cardboard across the inlet to the throttle body. the car should die. have some one watch the boost gauge. the car should go into max vacuum before it dies. so the needle should slam down to the bottom. if the engine stumbles for a second like its trying to stay running. if you have a manifold leak you should be able to hear it because the motor will try to suck air from everywhere in order to stay running.

as far as boost...? are you building boost at a normal rate of speed...? or slower...?

10psi spring is just the max PSI that boost has to over come in order to fully close the wastegate. from there exhaust stream flows completely across the the turbine wheel instead of bypassing allowing for full boost to build. it will build until you max the turbo's capability or blow a head gasket. which ever happens first. it doesn't mean thats wha your turbo max boost potential is.

now the vacuum leak should have no effect on your driving at 5k rpms... but then again this is a turbo car. and vacuum leak could mean boost leak.

is your boost gauge mechanical... or electrical...?

[SW20OWNER]

The simple way to check for vacume leaks is to spray carb cleaner or engine start spray or an excellerant around the area that you think is leaking while the engine is running.If the engine RPM's increase, you have a leak...good luck

[jesse0880]

cool, when i get some time i can do all those procedures to check for the leak. so thanks.

my gauge is a cheap 20$ mechanical gauge from twosrus.com which works except that the light bulb that comes with it messes with the needle when the bulb gets pressed in to far. well, now even when the bulb is out, the needle sets about 1 in of vacumn so im gonna use a real vacumn gauge to check soon. so maybe its boosting about 9-10 psi instead of what the cheap gauge is reading. i'll let u guys know.

[jesse0880]

yep, there was a reason why my boost gauge was only $20. i used a new vacumn gauge and there it was, about 16.5-17 inhg and the wastegate started to bleed psi right before 10psi. the whole time the boost gauge was 3 in of hg off and then 4 pounds off on the pressure side.

i always thought i was having a problem at 5k because of the lack of power and the noise. well, i figured out the noise... its the ext. wastegate opening cause its not recirulated back into the exhaust. i noticed i hear it as soon as my boost gauge hits its peak in pressure. today i actually tried to bring the rpms up to 7k and once it went through 5k there was still more power being made. it was kinda like power climbed to 5k and leveled off till 5500 then started climing again. now i guess my main problem now is getting my car smoged.

thanks for the help guys