Wow lots of freaking out in this thread.... do a proper boost leak test, that is:
1: Unplug the hose coming from valve cover to intake. ( cap the hose with something so air does't go out)
2. charge the system from the intake pipe with the same amount of psi you car would normally hit
3. have some soapy water ready to find smaller leaks.
Done.

 

He didn't do the test properly. He pressurized his valve cover. Breather hose needs to be unplugged

 

You're right , unplug the valve cover vent hose going to the intake pipe(valve cover side) and plug it up. I used a triple A battery

 

The hose from the PCV valve to intake manifold should not be removed. The valve is something that closes when pressurized, so it should be connected when doing a boost leak test.

 

If your losing oil. I would do a proper leak down test to determine if its the rings. A compression test cannot fully determine if the piston rings are bad.

 

We are not talking about the hose from PCV to intake mani, we are talking about the hose from valve cover to intake HOSE, the one between MAF and turbo.
Unplug on the valve cover side and cap it off ( triple A battery as suggested ) then run the boost leak test. Otherwise you will have air coming from the oil cap and a bunch of odd places.
Ed

 

There should not be any air coming out of the valve cover unless there is excessive cylinder blow-by, or if the PCV is defective, allowing air into the valve cover. It won't hurt to plug that line, but you will be overlooking the possible other problems that may be present.

 

Ok I see what you mean... you perform your boost leak tests at the turbo right? well other people like myself do it removing the maf only, so the intake tube is kept, and if we send air through there it will obviously go through the hose to the valve cover, where there is no PCV valve, just a nipple for the hose to plug in, see what I mean? So, if the test is performed from the turbo on ( removing the intake tube all together) then yes you are correct, if the test is performed from the maf (removing only airbox and maf) then that hose MUST be unplugged and caped, because air WILL get into the valve cover and ruin the whole test.

 

Very true.

I didn't even know people did a boost leak test before the inlet pipe.

It seems like the diverter valve would open too easily using that setup. It is not designed to have pressure from the outlet side.

 

Even if the diverter valve opened you wouldn't lose any air from the system since it is plugged effectively at the MAF. The only downside of this is you won't be able to tell if your DV DOES leak under normal conditions or not.

 

do it the proper way, because laziness has most likely caused you more headaches and time than it would have taken to remove the intake.

steps previously mentioned:
1. remove intake assembly, plug hose off of valvecover vent.
2. attatch boost leak tester to turbo inlet directly.
3. Plug vac line from compressor housing to MBC, if you have one
4. pressurize the system... watch boost gauge. dont go much more than tuned boost levels.

tips - try to do this with the compressor at a full charge. when they kick on they are ****ing loud and good luck finding the small leaks.
-soap and water from spray bottle works great.

If you do it that way, and you still have air coming out of your oil cap... something is effed. start cheap (pcv) and work you way from there.

 

I've performed all my test this way and have had no problems ever, I found a couple leaks and fixed them. What do you mean that you won't be able to tell if the DV leaks? it's seeing the same pressure you send to the rest of the system.

 

Here's my terrible MS paint picture of the intake system. You're putting your leak tester and pressurizing from where it says "Intake". See how you'll pressurize both sides of the DV with the same pressure, so there wouldn't be any leakage? Normal operation is pressure starting from the turbo, so the intake side of the DV would be atmospheric pressure, and the upper intercooler pipe side would be boosted. You're having both sides boosted.

You'd catch all other leaks though I believe.

 

lol awesome drawing I see it now, you are absolutely right, I will have to make myself a new tester that fits the turbo inlet... thanks for the heads up

 

my gsx does this all the time, its the seals on the turbo thats letting air go by and then down the oil return line and into the oil pan, thus pressurizing your block,, when turbos are cold, a lot of them will not seat with air pressure alone, when the motors on and running, the oil pressure will seat those seals and there wont be any of that going on anymore. but yes check your PCV valve, get a mitsubishi replacement, the AutoZOne replacement is junk and will not work, I personally have a check valve inbetween the PCV valve and the intake, i got sick of dicking with the PCV valves and bought the check valve that will hold 150psi, im glad i did it and i have had no issues since