Boost leak questions

[Dave_GSR1.8]

So, the time has come to check for boost leaks, searched the forum, watched the Mighty Car Mods video, bought the parts etc etc... but just wondering, when connecting it up where exactly does one do so ? It seems there are several possibilities;

1) just after the turbo and blank off the piping just before the TB (the MCM approach)
2) just on the mouth of the turbo and blank off the piping just before the TB (one variation)
3) just on the mouth of the turbo and leave the rest connected (will highlight any problems with TB and injector seals) but won't this leak too fast past piston rings and any open valves to give useful results ? And can the turbo leak enough to be an issue ?
4) just after the turbo and leave the rest connected (same queries as 3 but without the turbo in the loop)

What do you guys do ?

Edited to make it read better (preferred evo-gsr's wording)

 

[evo-gsr]

Straight on the mouth of the turbo. Will find a leak anywhere in the whole system then.
Tried and tested method here. No Internet mechanic ********.

 

[Ian91]

Yep I went straight into the turbo inlet, leave everything connected and it will show any leak from turbo to intake mani

 

[evo-gsr]

It will show any leaks full stop. ^

 

[4piknup]

Agree, mouth of the turbo, as is.

but....engine needs to be not on tdc, so you dont have air pumping straight in intake valve and out open exhaust valve. Its pretty unlikely that it will stop at that exact point tho.
also, you are going to have at least one intake valve open, so that means one cylinder is charged with your test pressure. This means some of the rate of pressure drop on the test will be attributable to the rings of that cylinder. (Similarly, a leaking intake or exhaust valve will affect rate of pressure drop).
You need to slightly allow for this, my engine, I believe shows a quicker pressure drop than I would like, tho this is past the rings not from any intake leaks.

I still have a for sale of some throttle shaft seals from when I did mine. I ordered a few extra as made no difference to postage.
You have to really spray plenty of bubbly water around to spot the leaks.

 

[evo-gsr]

You should be able to hear the leaks quite clearly. Especially with a few psi being put into it.
I have never used the soapy water idea as the hiss is easy to find...but each to their own.

 

[Ian91]

Yea same, found and fixed all my leaks by hearing and feeling the air coming out

 

[4piknup]

So how well are they holding the test pressure? Say to leak to 1/2 pressure.
If the test pressure is 20psi, how long to get from 20 to 10 psi?

 

[Ian91]

Didn't bother checking that because I figured it would leak through the valves. I just pumped 20psi into the system and left the tap open on the compressor so it put pressure on long enough to find the leaks, but at 20 psi the valve leaking must be minimal because it blew the tester off the front of the turbo when I bumped it up to 25

 

[evo-gsr]

Exactly ^
Shuddup Jack.