Boost leak test help

[Dingo]

I'm having hesitation problems on my car and was advised that I've got a leak, I've checked the turbo side and am happy its leak free but need some advice on the inlet side.
I placed the bung (Andy P) into the throttle body and pressurise to 1.5 bar, I can not hear any leaks at all but the pressure slowly drops off, my question is.... have I got a leak or is the air escaping past the valves and rings, is this normal, I'm pretty sure I hav'nt got a leak but am at a loss as what to do next.
Brian

[UrS4boy]

3B, ABY and ADU boost leak pressure testing

I'm having hesitation problems on my car and was advised that I've got a leak, I've checked the turbo side and am happy its leak free but need some advice on the inlet side.

I don't think you are testing for leaks in the correct location.

Have a read on this:

http://www.s2forum.com/forum/showthread.php?t=63974&highlight=boost+leak+testing

[Dingo]

I've allready tested the turbo side, (pressurise MAF hose, remove breather and bung) but then to test all the rest I isert bung in C1 (your diagram) to pessurise all the inlet side !

[UrS4boy]

I've allready tested the turbo side, (pressurise MAF hose, remove breather and bung) but then to test all the rest I isert bung in C1 (your diagram) to pressurise all the inlet side !

" The table was set up to isolate certain components. Many people, most notably prj (dmitri), have suggested that the simplest method of boost leak testing that captures all the possibilities in one go is to place the pressure bung in "A1" in the diagram and disconnect the hose from the cam cover to "A3" and plug "A3", leaving the rest alone. This falls some where between test Option 1 and Option 3."

[Dingo]

I think were at cross purposes here, the test that you discribe I have allready done and was successfull, but in addition to that I also test at the throttle body (at prj request) so it can be put under greater pressure (1.5 bar) without stressing the concertina MAF hose, both these tests were done successfully but I just need to Know ........ is air escaping past the valves & rings.
many thanks

[UrS4boy]

I think were at cross purposes here, the test that you discribe I have allready done and was successfull, but in addition to that I also test at the throttle body (at prj request) so it can be put under greater pressure (1.5 bar) without stressing the concertina MAF hose, both these tests were done successfully but I just need to Know ........ is air escaping past the valves & rings. many thanks

You could do that easier (maybe) with the pressure bung in B1, the turbo outlet hose (My option 4).

As for pressure leaking past valves and rings at 1.5 Bar, sure, maybe. Not sure what it would prove (assuming a very slow leak). Just remember that the compression spec for these 20VT engines is in the 9 to 13 Bar range. If your bleeder valve isn't holding, there will be boost leakage into the PCV system.

[Dingo]

Ok, thanks, I'm just trying to rule out a boost leak and was wondering how it was escaping before I throw to much money at this, I've allready replaced
plugs & boots
N75 valve
recirc valve
the car is throwing no codes but will only boost to 1.3, 1.4 bar now and used to boost to 1.6, 1.7 (homefried N stream)
I am now leaning towards coils or MAF, but since I carnt test these I'm only guessing

[Rikki Kitto]

Just sorted a boost cut problem on mine, turned out the wgfv had been put back in wrong

[Dingo]

wish mine were that simple

[minim]

You will always have a air leak testing like this but the question is how big it is. I don't know how long it should hold pressure but often there is a spec like "apply 1.5bar pressure and it should not sink below 1bar in 30sec". Did you look in the workshop manuals for a test procedure for these engines? The time/pressure was just as an example, don't use that for anything.

[Dingo]

Workshop manual, if only. No I'm only being guided by what i've learn't on here.

[UrS4boy]

Workshop manual, if only. No I'm only being guided by what i've learn't on here.

Umm...you *might* want to look at this website:

http://www.s2-audi.co.uk/work_shop.htm

[bilko0795]

I found that after sorting my leak ,I still had hesitation it turned out to be the maf of which is now NLA as of six days ago, the car now runs as it should with the new one fitted. I was lucky as I had the last one in the Uk on Saturday. I believe you may get one on fleabay if indeed it turns out to be the maf. I borrowed one from Rusty on here which is a good working one and that's how I found out it was the maf.

[Dingo]

Thanks for that website, plenty of reading for me to do

[UrS4boy]

Thanks for that website, plenty of reading for me to do

You need to down load and save those engine manual pdfs. They will come in handy in the future.