For sometime now I've been getting only 7" of vacum. I think I might have a possible rip or leak some where in the system.

The car seems to hit boost fine on 10 lbs but when I go to 14 the car sputters from 6K-6.5, my guess is that there is some relation between the sputtering and low vacum.

What would be the best way to test for a boost leak?

 

Use of a smoke machine would be an idea. Most only generate a couple of psi (2 psi or less) but if you are also leaking vacuum it should do the trick. Works great for finding air leaks on late model driveability related problems. Example P0171/P01714 DTC's. On 5.3L Chevrolet truck engines I see this alot and it turns out to be the intake manifold gaskets.

 

I've done a smoke test to check for any vacum leaks at the intake manifold and everything looked fine.

Would it be a good idea to run it through my turbo system?

 

Vacuum is pulled behind the throttle body, you don't need a boost leak test you have to findout how air is getting by the tb, Check your IAC to make sure it's not seized up keeping the tb slightly open.

 

it looks like it wasnt tuned by you.... it could be the tune needs a check...

 

If you want to test for boost leaks you need to put a cap on the turbo inlet and pressurize the entire intake system. Thats how we have always done it on any of the cars we have built.

 

Smoke machines work great but not everyone has them available in their garage. the next best thing is to build your own boost leak tester for <$10.00 @ Home Depot and use an air compressor. If you don't have an air compressor in your garage you can even go to a gas station and use the compressor they have outside for filling up tires.

You need to find a Fernco coupling the same size as your compressor inlet (what your air filter is connected to). So if your not sure what that is take a measurement of the OD, and look for a coupler with the same ID. If you can't find a fernco in your size you might need to order a silicone coupler with the correct ID. Next you'll need a PVC cap to fit in the fernco (or silicone) coupling.

then you just drill a hole in the PVC cap and install either a tire valve stem or a scrhader valve in that hole. Make sure you seal the thread for the valve with some kind of sealant, anything will do just as long as it doesn't leak.

Now that you have your cap with a valve put together you need to install that on your compressor inlet (that part where the air filter goes) with a good set of clamps so it doesn't leak or worse pop off on you, and use an air compressor to fill the intake piping with air and listen for leaks. It needs to be very quite where you are doing this so you can listen for air. SOme leaks are very small. If you can hear it but still can't find it try wetting your hand with liquid and feel around the area where the noise is, usually that work.

Doing this is like simulating the turbo or SC making boost. You might want to have someone handy to watch your boost gauge, make sure you don't go higher then 15psi MAX. You will be AMAZED how many you find.

 

Thanks for the help everyone. I'll probably to some tests this week and hopefully get this issue resolved

 

Here is how I made up a leak tester.








Went to homedepot got some fernco's reducers that would fit a 3.5-2.0 inch tubing (cuz I had the 3.5 lying around) and two 2.0 cap/couplers. They are the white PVC items in the fernco's.

Bought a package of valve stems from pep boys, drilled a hole in one of the 2.0 caps, pushed the valve stem through. Screwed the non drilled cap into the other PVC fitting and clamped it all together.

I had the 3.0-3.5 silicone reducers handy as well as extra clamps.

I'm able to check parts of my IC tubing or the entire system(last two pics) just by pressurizing the set up to 10psi and then checking for leaks with soapy water or leaving it for an hour and checking the pressure with a tire gauge.


Works awesome and didn't cost much money.

 

thats great you made that setup and all but the idea behind leak testing is to use the compressor inlet so you don't have to remove/reinstall any charge piping. Otherwise when you reinstall that intake elbow on the TB how do you know there aren't any leaks?

 

frcefed98: Great info!! I'm going to HD tonight and probably do a compression test tomorrow. Thanks again

 

good idea... could do this on the hot side on a turbo setup also (if homebuilt and checking for leaks). If you spray windex on all the pipes it should bubble where the leaks are. easier to find than listening around.

 

I know the idea behind the of leak testing The connection at the compressor outlet and TB inlet weren't of any concern to me, its the reason why I have it the way I do in the pics. If it were a concern to me I would have put the valve stem side of my set up into my air filter boot (3.5 in) and pressurized the turbo to the inlet of the TB BUT>>>>>>>>

The compressor outlet and the TB pipe are in plain view and easy to secure with my t bolts and to check for damaged silicone or misaligned or loose clamps. Pretty easy to tell if there will be a leak or not at these two points.

NOW with the rest of the charge piping especially if its on the car which is mostly hidden out of view its not so easy to see if there is a hole rubbed through the silicone at any point or if there is a loose clamp or misaligned clamp, so the beauty of my set up comes into play. Test it from the outlet of the compressor housing to the TB. You'll be able to tell if there is a leak at any junction or even if the BOV is leaking all while its on the car.

I could even check the intake manifold by putting the pressure side of my set up onto the TB charge tubing, taking off the VC's and unbolting the rocker arms to make all the valves close and then pressurizing it. Be a easy way to see if the intake manifold gaskets are leaking etc..


Good enough for you?

JD, glad I could give you a visual on making a set up like this.

 

wow! you guys come up with some cool stuff.

 

Got to, most of us don't have a "smoke machine" in our back pockets.

Comes in real handy for sure, I was rushing to get the car back together for an outing at the track and while I was there I was down on boost big time. Got it back home and put my el cheapo pressure testing set up on there and it helped me find a huge leak, I had a misaligned T bolt which allowed the silicone coupler to slip out about an inch that caused the leak. Reason it was misaligned in the first place, the silicone connector was up in the nose and hard to get to and tougher to get an eyeball on, couple that with being in a rush and you have one nice leak.

 

I have used the old Home Depot trick as well and it works great, just capped off all my piping and pressurized it to 13psi and let it sit for a while. Then checked the pressure with a guage and no drop so good to go. Its amazing how much air it actually takes to pressurized the piping and intercooler.

 

it fine with me if you want to do it that way, seriously, whatever makes you happy.

but again the point of doing a boost leak test is to eliminate leaks. by pulling off sections of charge piping and testing them individualy you defeat that purpose.

after you've reassembled the pipes how will you know if there is a leak or not? its a fact you can't tell by looking at a clamp if it leaks, thats the whole reason why your doing the boost leak test in the first place. it doesn't matter if its a t-bolt, worm clamp or ziptie because they all leak.

Doing a test the correct way you would leave all your charge piping in place and pressurize your system @ the compressor inlet. that way you mimic how the turbo/sc makes boost when the car is running.

 

JD-Z28 post up when u do it if it makes a difference cause i only see 8-9" of vacuum on my setup which i think should be more as well.

 

Ok ok you win

 

I should have it done this week, I should have the results this weekend.