Hi All,
I was performing a boost leak test and found that there was air coming out of the engine from the valve that goes back into the intake. I've read a lot of mixed responses on why this is happening:
Oil seal in the turbo isn't sealing since the engine isn't on. (though I've heard this is only non-stock turbos)
Valve seals are bad
Piston rings are bad
PCV valve is bad (checked this. No air was entering the engine from the valve)
it's just supposed to happen

I'm connecting the boost tester to the turbo (removed the intake). I left the ebc on but regardless it doesn't explain air coming out of the engine.
I've considered capping the valve during the test but im not sure it's safe to build up all that air pressure in the engine.

Car specs: evo 9 with 62k miles. Looks like I have a stock turbo I checked the numbers and the aluminum side matched up.
Mods that may matter include: All exhaust including O2 housing and headers. AEM truboost.
Car is tuned for 24 psi and seems to hit that fine. It was running rich before tuning so I'm assuming the engine is seeing less air than the MAF?

If anyone has any insight on what can be the cause please let me know

Thanks
Jon

 

Is the engine at TDC? IIRC the engine position will affect where air leaks and how bad.. Hope this helps

 

I've tried cranking it with the 1/2inch drive to tdc and Ive tried just any old position and both ways air still came out. Couldn't say for sure if the flow varied though.

 

Well time to start deducing.
Are there people with an evo 9 and stock turbo who do not encounter this?
How about evo 8 anyone encounter or not encounter this problem?

 

the 2 fittings for the pcv valve and fitting that goes to intake like you're explaining needs to be plugged before you do your boost leak test

 

So there is the pcv valve on the back left of the engine which only opens when the engine pressure exceeds the intake manifold pressure. and then there's the valve torwards the front right that connects to the intake. If I block this there will still be air pressure building up in the engine. I guess the question is: is it normal to build up significant air pressure in the engine under a boost test? I can't imagine the oil cap holding 20-30psi

 

the boost leak test is not to test if the engine can take pressure, its for the acessories ie; intake, intercooler piping, throttle body, fuel rail and such aren't leaking. and yes those valves you just mentioned need to be plug. i've never had an issue with my oil cap.

 

Okay I'm going to try this when I get a break one of these weekends. I guess worst case the oil cap or dipstick will pop off once I hit 25 psi.

 

Ive wondered the same question and had the same issue when I tried it. I plugged the crank case vent and stuff but still had issues... Let us know what you find.

 

What issues did you end up having?