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Old 09-01-2015, 08:59 PM   #1
antilag
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Default What to disconnect / block for boost leak test

I am planning to do a boost leak test soon and have some questions about what to block off. I've tried searching through threads but I am finding some conflicting info without definitive answers, and a few things aren't clear to me.

Here is everything that seems to come off of the turbo inlet hose:

1. Turbo inlet hose <-> boost control solenoid
2. Turbo inlet hose <-> EVAP purge valve
2a. EVAP purge valve <-> intake manifold
2b. EVAP purge valve <-> ??
3. Turbo inlet hose <-> breather lines to heads
4. Turbo inlet host <-> BPV
5. Turbo inlet hose <-> crankcase breather
5a. PCV valve <-> intake manifold


As far as what to do for each one:
1. I think that I can leave this one as-is?
2. This one I believe I need to remove and cap/plug.
2a/b. Do I need to remove/cap any of these? Some people mentioned disconnecting the line to the intake manifold and plugging the manifold. Is this necessary?
3. I believe I need to remove this and cap at the inlet hose. What about the lines from the heads? Should I just leave them unplugged or block them?
4. I think I can leave this on as-is?
5. I believe I need to remove this one as well and cap it.
5a. I'm not exactly sure what to do with this. Do I leave the lines between the crankcase and intake manifold with the PCV valve as-is? Do I cap it, or do I need to separate it somewhere between the crankcase, PCV valve, and intake? I'm planning to take the oil cap off, so I don't know if that has any influence on what I need to do here.
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Old 09-02-2015, 09:39 AM   #2
Bpat1218
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It really comes down to what you want to test for a leak. You can include or choose to not include a number of the fittings.

Block off anything that goes to the crankcase/pcv system. You could first block all of the small fittings on the intake and just test the pre-turbo to throttle body route. If there's no leak there then its somewhere else. Reconnect a fitting and try again.

There's really no cookbook way of doing it you just have to work through it and eliminate all of the possibilities
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Old 09-02-2015, 11:32 AM   #3
antilag
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Thanks for the info. I was mostly just trying to determine what I need to do to perform the test safely and avoid damaging anything. As long as I disconnect / block the line from the turbo inlet hose to the heads and the one to the crankcase/intake manifold, and take the oil cap off, I should be safe then?

The T between the crankcase breather, turbo inlet hose, and intake manifold (with a PCV valve in it) was the biggest part I wasn't really sure about as far as whether I could just cap the turbo inlet hose here or if I needed to further take things apart.
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Old 09-06-2015, 08:38 AM   #4
Vlad
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This has been discussed many times and would benefit from a sticky.

When I was doing this often, there were two active threads about doing this and you could see that there were two categories of posters, for the EJ205.

There were some that accomplished (or said they accomplished) the test with a clear result indicating one way or another and some that said the test could not be performed because the test rig could not hold air.

I thought that this may relate to the position in which the engine stops. I think there is a whole theory of the position in which an engine stops and possibly, in time, it stops only one way (same position of cyl 1-4). If this is the case, some engines stopped in a way where they could not pressurize, while others did not.

People that posted more details complained that the air seemed to come out of the exhaust.
So, when I could not get the air to pressurize, I started to move the crank, with a big socket from the pulley, going in the direction of engine rotation.

There definitely is a position that enables the test.

Now, I think that pressure testing the intake hoses and testing the heads are different things. Meaning a successful test of the hoses is where you will get the system to hold 5-10 PSI, no more.
The people that posted successful tests probably skipped this detail.

The thing is that some of the path that you are testing is made of hoses that operate under vacuum moderate to really deep, never under pressure. So they are not designed to hold pressure.
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Old 09-06-2015, 11:34 AM   #5
antilag
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I just finished doing this. I was able to get it to hold pressure without moving the crank or anything, but only about 10 PSI. At first I thought it might be the compressor I was using (it was just a tire inflator), but I did not disconnect/plug every intake hose from the turbo inlet hose so that may be it.

As far as disconnecting things, here is what I did:
1. Disconnected the line to the EVAP purge valve and capped the inlet hose there
2. Disconnected the lines from each side of the hard line on the front of the intercooler and plugged both sides of the hard line
3. Disconnected the crankcase breather line from the turbo inlet hose and capped the turbo inlet hose there

I didn't touch the BPV and BCS lines on the inlet, and I didn't plug any of the disconnected hoses. I mostly chose where to cap things based on convenience and what I had to use for plugging. The locations weren't really optimal for the test itself though.

I was able to find a leak between the turbo inlet hose and the turbo (spraying soapy water). I tightened the hose clamp and retested, and it seems to have gone away. I didn't find any other leaks, but I don't know if I missed any (I've seen people say that leaks didn't show up until a higher PSI).
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Old 03-24-2021, 06:19 PM   #6
pcampbell
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Does this not hook directly to the intake manifold, but to the intake (before the turbo)?
This is the part I am talking about:
https://parts.subaru.com/p/Subaru__/...b-9Vl9xEXFfwzA

Last edited by pcampbell; 03-24-2021 at 06:32 PM.
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