Boost leak testing clarifications needed

[xt2005bonbon]

After all these years, and even going through one engine rebuild, it is still unclear to me exactly which hoses need to be clamped when boost leak testing our engines. I know, shame on me. Did go through Youtube, other forums and still could not find exact answers to my questions (for our engine layout in particular).

Anyway, I know what tools to use to perform a boost leak test. I also know the oil cap needs to be removed for safety. So, here is a schematic of our intake hose and manifold. My understanding is that the red circled connections on our intake hose need to be capped off.

Question 1: is this correct?

Question 2: anything else need to be capped off?

Question 3: do we need to do something about the PCV valve?

I'll update this thread with your answers.

 

[Max Capacity]

All I do is put a pint size paint can into the big hose coming off the air filter box. Then pull the small hose off the Blow Off Valve and give that hose a short blast of air from my compressor, put my thumb over that small hose and listen for leaks.

EDIT,

By short blast of air, I mean maybe for 1 or 2 seconds, anymore, and you risk blowing some hoses off.  Remember, your compressor may put out more or less PSI than someone else's.  The idea is to fill with enough PSI to hear a leak, not blow things apart.  Use your head. It doesn't take a lot of PIS to hear a leak.

[xt2005bonbon]

That's what I have done for years. But I don't think this method may work if you want to truly check for boost leaks which may show up only in higher boost situations.

[m sprank]

To do it right you cap none of the hoses and you connect your smoke machine to the intake tube.  Best machines test at around 14psi.  You can add UV dye to the liquid and then you can use a black light and glasses to see the leak even if you saw no smoke.  The smoke has a smell too, so sometimes you can pick that up. 

 

Otherwise you wont find a definitive answer as there is no definitive procedure. 

[Max Capacity]

https://www.google.com/search?q=smoke+machine+for+vacuum+leaks&rlz=1C1OKWM_enUS906US906&oq=smoke+machine&aqs=chrome.3.69i57j0i512l9.10507j0j15&sourceid=chrome&ie=UTF-8

 

The problem is, most of us are too cheap to buy the machine...

But as these cars age, the smoke machine could be helpful chasing Evap leaks.

[KZJonny]

I picked up the Autoline one, which was actually really well made. Worked a treat, and I've loaned it around some to others who were in need, so it's getting used, and I think, worth the money. (It was a fair bit cheaper last year than now...)

It does not do more than 1 psi through it's own regulator, which is fine for most applications and safe for general use. However, another GT owner in the area made up a 3d printed plus which fits into the intake tube, and has a barbed port to attach for smoke as well as a Schrader valve glued into it. Works great, and could easily be replicated with a paint can lid or whatever you have.

Just fill the system entirely with smoke, and swap the compressor line over to the Schrader valve and fill to desired pressure. Takes secods to do the swap, and I guess that way you can check at whatever psi you want to look at. I would think as long as you pre-set the regulator to the desired pressure you'd be good, and if you forgot you'd blow some hoses off! (Just thinking my compressor runs to 120psi and I have it throttled down to like....90psi at the reg/filter...)

 

1 hour ago, m sprank said:

You can add UV dye to the liquid and then you can use a black light and glasses to see the leak even if you saw no smoke.

Never though of this. Smaht.

[xt2005bonbon]

On 3/7/2023 at 11:50 AM, m sprank said:

To do it right you cap none of the hoses and you connect your smoke machine to the intake tube.  Best machines test at around 14psi.  You can add UV dye to the liquid and then you can use a black light and glasses to see the leak even if you saw no smoke.  The smoke has a smell too, so sometimes you can pick that up. 

 

Otherwise you wont find a definitive answer as there is no definitive procedure. 

Let's call the above method the optimal one. I can see why as you do not disturb the system (by disconnecting hoses, etc..). Do you leave the oil cap close btw in your described method?

 

Now, onto the not so optimal method described here and more or less applied in this video. This is essentially what I would like to try. Problem is it is an STI intake manifold and intake hose, so slightly different. And I got a little confused as what hoses she capped off in the end. So, if I wanted to replicate her method, exactly what do I cap off on our engine?

[m sprank]

When using a smoke machine you do not cap any hoses.  You leave the oil filler neck cap intact.  You are not going to damage the engine as you are not going to pressurize beyond stock boost.  Damage occurs from the air compressor and excessive pressure.  So, they recommend removing the oil filler neck cap.  Its like saying, "you know what you are doing is dangerous, so be careful".  Not OSHA approved, LOL. 

 

I dont understand capping any lines.  The vacuum lines are a source of leaks.  Hoses and fittings leak in vacuum and boost.  Maybe the cap you use does not leak, but your hose that you removed, and did not test, does.  The point is to leave the car as it is when driven so you can test in the driven state.  Sorry, not much help with this. 

[xt2005bonbon]

No, I totally get your point. And that is another reason why I never really tried to do the test I mentioned, since you 'disturb' the system by removing/disconnecting hoses.

It's interesting though because I am pretty sure I don't recall seeing any online videos showing what you are describing (i.e. leave everything intact and pressurize the system with the smoke machine). Maybe I am blind and don't know how to search

 

Edited March 9, 2023 by xt2005bonbon

[m sprank]

I had a cone that fit perfect into the post MAF hose.  We pressure tested from there.  Removed nothing else.  Could insert into the tailpipe and run smoke all the way to the evap solenoid at the intake manifold.  Worked for boost and evap leaks. 

Education is not free. I have never watched a vid of a procedure I was well aware of and saw all the proper steps taken.  It is my personal belief that those that really know dont tell you everything because thats how they make a living and those that pretend to know show you wrong.  

[xt2005bonbon]

Looks like this guy, which I believe is a Subaru tech, is following the method you described. However, he does not mention anywhere the pressure level (if any) the smoke machine is applying to the system.

And then, you read articles like this one from reputable sources which confuse you (i.e. saying you need to clamp some hoses).

 

Edited March 9, 2023 by xt2005bonbon

[m sprank]

From the first vid the machine is pushing 12-14psi.  I can tell by the hook ups.  I am familiar.  His method is very similar to mine.  His shirt looks like a dealership tech uniform.

That motor trend article is GHETTO.  They should be ashamed of themselves and remove that. 

I have recently seen smoke machines advertised in the $200 price range that when combined with a low output compressor would work perfect.  Dont need a $3k machine.  But damaging a $6k engine with an air compressor seems like a bad idea when a tool can be had for under $300.  My $0.02.

Edited March 9, 2023 by m sprank

[silverton]

TIL motortrend is a reputable source and not just a magazine that belongs in the checkout aisle at grocery stores next to the national enquirer...

[blackobxt]

Is the fear that’s pasted all over the internet  that pressurizing the crank case runs the risk of blowing cam or crank seals out and that’s why you should cap them? I’m with m sprank on that it’s user error from way over pressurizing the system. I’ve boost leak checked via pressurizing tons of vehicles without capping lines and never had any issues with blowing out seals.

[xt2005bonbon]

5 hours ago, m sprank said:

From the first vid the machine is pushing 12-14psi.  I can tell by the hook ups.  I am familiar.  His method is very similar to mine.  His shirt looks like a dealership tech uniform.

That motor trend article is GHETTO.  They should be ashamed of themselves and remove that. 

I have recently seen smoke machines advertised in the $200 price range that when combined with a low output compressor would work perfect.  Dont need a $3k machine.  But damaging a $6k engine with an air compressor seems like a bad idea when a tool can be had for under $300.  My $0.02.

You $0.02 is much appreciated. And yeah, shame on Motortrend..

3 hours ago, silverton said:

TIL motortrend is a reputable source and not just a magazine that belongs in the checkout aisle at grocery stores next to the national enquirer...

. I mean, I did enjoy watching Roadkill when it was free on Youtube..

 

2 hours ago, blackobxt said:

Is the fear that’s pasted all over the internet that pressurizing the crank case runs the risk of blowing cam or crank seals

Edited March 10, 2023 by xt2005bonbon

[m sprank]

Yes.  Blow past the seals. Lets think about this. A turbo Subie can push 40psi oil pressure at idle and a good 100psi+ (depends on build) at WOT and full boost.  So.....   wtf are you doing hitting your intake with 120psi of air pressure?????????? 

You tube.  For those who grew up with Chilton repair manuals we say FU You Tube. Stick it where the sun dont shine. 

[silverton]

You can't talk to me that way! *Points towards my embroidered technician shirt*

[blackobxt]

14 minutes ago, silverton said:

You can't talk to me that way! *Points towards my embroidered technician shirt*

Man I need to buy these and start handing them out