Easy 5th Gen GT Boost Leak Test

Background

 

This test was recommended to me by Tuning Alliance, but I will add more detail specifically regarding the 5th gen GT as details are fleshed out. Over time, photos and detailed steps, likely leak points, etc.

 

This process tests the entire intake tract from valves to your plug in the inlet. It will detect the presence of any leak big enough to cause boosting issues and leaks smaller that probably don't cause issues to boost or AFR but could cause other issues (like the PCV valve leaking boost pressure into your crankcase and blowing out crank/cam oil seals).

 

 

Step 1.

 

Pull out the airbox, or whatever you have instead of an airbox if not stock. Remove it completely because you need access to the opening to the inlet pipe.

 

Details, directions, etc. to follow, but if you are diagnosing a boost leak you probably don't need help getting your airbox out.

 

 

Step 2.

 

Plug the inlet pipe after the MAF (i.e. where your airbox used to be connected). It has to be air-tight but only has to hold 5 - 10 PSI so nothing crazy. You can use anything that is the right diameter along with the OEM or other clamp, like a tin can or maybe a hockey puck?

 

I used a 3-inch plumbing test plug like so, because it fits in and tightens up from the inside, combined with the clamp it makes a nice seal and is easy:

 

Moen 3" Test Plug from Home Depot

 

Step 3.

 

Pull the vaccum line off your BPV/BOV, feed the tube back and up so you can reach it with your mouth to blow in it.

 

Step 4.

 

Blow into the tube. You are looking to make about 5 PSI. Don't have a boost gauge in your cheek? - Time for an upgrade. Seriously though, blow gently until you feel resistance. You shouldn't be able to blow more than one deep breath into it. You are basically compressing all the air in your manifold, intercooler, charge pipe, and inlet pipe.

 

If you plug it off with your thumb, hold it for 5 - 10 seconds and it whooshes back, then you are free of boost leaks. If not, then you probably have a leak and it's time to start hunting it down.

 

Aside

 

If it is leaking, I'd advise you to check your PCV valve, since that is highly likely to be leaking if it's been more than 20,000 miles since it was last changed, and it probably has for most people. It's easy to check by pulling the vacuum line off the top, plugging it with something (a pen, your finger, whatever) and blowing into system again. If it can hold air now, then you PCV is to blame - replace it.

Edited August 10, 2016 by brandon.mol

Reserved

Ok I used this method yesterday and if I held it for a 5 count there was still pressure but 20 count not so much. When I hooked my air compressor to the bpv signal line air was coming out the nipple on my bpv as well as around the bpv flange and the charge pipe flange. I put a new gasket on the cp flange today and still not hitting peak, I got up to 14.6 psi and then tapered down from there.

 

I will reseal the bpv tomorrow and then try the test again to be sure the CP flange is leak free.

Edited August 28, 2016 by FLlegacy

No metered air should be flowing out through your BPV nipple. That would indicate to me that your BPV is leaking. That seams odd though...

This had me thinking: if the signal side of your BPV piston is exposed to the pre-throttle-plate intake pressure, which it must be, since said air is flowing out the nipple, then it will never open to do its job since there is no pressure differential across the piston.

 

So that's bad.

 

Mind you, if that's happening, it's probably pissing air out the low pressure side too accounting for your "boost leak". But since that air is being lost to the inlet post MAF, it will won't impact AFR.

 

I assume you have an aftermarket BPV?

Edited August 29, 2016 by brandon.mol

Yes a turbosmart kompact bpv, I may put the stock charge pipe back on to see whats what. I also pulled a hose when I dropped the turbo so I need to check the small hoses on the bcs to make sure they are good, probably just replace them anyway.

 

I was thinking to run a direct hose from the compressor to the wastegate to rule out the wastegate actuator and to confirm a boost control issue, in my logs I am seeing the wastegate at about 40% dc when boost still isn't at target and throttle is at 100%. So I think something isn't holding, I am not seeing a sudden change in afr either.

 

I was running 16.5 psi before so I would think the bpv would hold at least the same, but maybe something else I am missing. I won't have a chance to check on it until Tuesday, so just living with it for now. No knock or leaning out so I am thinking I am not losing air or gaining air anywhere.

Edited August 28, 2016 by FLlegacy

Background

 

This test was recommended to me by Tuning Alliance, but I will add more detail specifically regarding the 5th gen GT as details are fleshed out. Over time, photos and detailed steps, likely leak points, etc.

 

This process tests the entire intake tract from valves to your plug in the inlet. It will detect the presence of any leak big enough to cause boosting issues and leaks smaller that probably don't cause issues to boost or AFR but could cause other issues (like the PCV valve leaking boost pressure into your crankcase and blowing out crank/cam oil seals).

 

 

Step 1.

 

Pull out the airbox, or whatever you have instead of an airbox if not stock. Remove it completely because you need access to the opening to the inlet pipe.

 

Details, directions, etc. to follow, but if you are diagnosing a boost leak you probably don't need help getting your airbox out.

 

 

Step 2.

 

Plug the inlet pipe after the MAF (i.e. where your airbox used to be connected). It has to be air-tight but only has to hold 5 - 10 PSI so nothing crazy. You can use anything that is the right diameter along with the OEM or other clamp, like a tin can or maybe a hockey puck?

 

I used a 3-inch plumbing test plug like so, because it fits in and tightens up from the inside, combined with the clamp it makes a nice seal and is easy:

 

Moen 3" Test Plug from Home Depot

 

Step 3.

 

Pull the vaccum line off your BPV/BOV, feed the tube back and up so you can reach it with your mouth to blow in it.

 

Step 4.

 

Blow into the tube. You are looking to make about 5 PSI. Don't have a boost gauge in your cheek? - Time for an upgrade. Seriously though, blow gently until you feel resistance. You shouldn't be able to blow more than one deep breath into it. You are basically compressing all the air in your manifold, intercooler, charge pipe, and inlet pipe.

 

If you plug it off with your thumb, hold it for 5 - 10 seconds and it whooshes back, then you are free of boost leaks. If not, then you probably have a leak and it's time to start hunting it down.

 

Aside

 

If it is leaking, I'd advise you to check your PCV valve, since that is highly likely to be leaking if it's been more than 20,000 miles since it was last changed, and it probably has for most people. It's easy to check by pulling the vacuum line off the top, plugging it with something (a pen, your finger, whatever) and blowing into system again. If it can hold air now, then you PCV is to blame - replace it.

 

would this process work with the racer-X charge pipe where bov is on the top?

Yessir. It doesn't matter where on the charge pipe the BPV is located.

Yes, I can confirm it works with either charge pipe stock or racerx.

 

And just to add to my previous posts my issue turned out to be the tune. The racerx pipe with the new gasket didn't leak and I still wasn't hitting target boost. As soon as Mike with tuning alliance turned up the wgdc I was back in business.

 

Sent from my SAMSUNG-SGH-I337 using Tapatalk

With the Racer-X, removing airbox seems to be hard. is it? The bov is right in the way.

It's a bit of a pain, but mostly because of the BOV recirc hose. I was thinking it might be easier to disconnect the part of the inlet pipe you can get to from under the car and plugging it there- wouldn't catch any leaks around the MAF sensor, but it'd get pretty much everything else.

Yes, I can confirm it works with either charge pipe stock or racerx.

 

And just to add to my previous posts my issue turned out to be the tune. The racerx pipe with the new gasket didn't leak and I still wasn't hitting target boost. As soon as Mike with tuning alliance turned up the wgdc I was back in business.

 

Sent from my SAMSUNG-SGH-I337 using Tapatalk

 

Hey guys.... Can you all tell me... What is WGDC???

 

THANKS APPRECIATE IT...

Hey guys.... Can you all tell me... What is WGDC???

 

 

 

THANKS APPRECIATE IT...

Waste Gate Duty Cycle.

Hey guys.... Can you all tell me... What is WGDC???

 

THANKS APPRECIATE IT...

 

Waste Gate Duty Cycle.

 

basically how long the wastegate is closed. It is normally wide open, until the tune calls for building boost then it closes or pulses closed to build turbine pressure and allow the compressor to start making boost.

I like the simplicity of this test but lets assume we figure out that we have a leak. ... could we use an EVAC smoke machine into the hose we blew into ? Or would it be better to figure out some cap with fitting on the intake side?