Crankcase pressurized when leak testing.

[seefour]

Whenever I boost leak test it seems like all of the pressure goes out through my catch can vent and if I pinch that line it goes out my dipstick. I just replaced my PCV valve with an OEM one and it still does it. I even tried blocking the nipple on the intake manifold to the PCV valve so I know its not the PCV.

Also, I'm not blowing out any smoke when I drive, so I dont think its rings or valvestems.

Thanks,
nick

 

[Tevenor]

Nick,

There are other ways for air to get in the crankcase other than the PCV valve. Around the rings for instance, depending on block condition. Usually a pressurized setup like that that is popping the dipstick means a leakdown condition.

Some pressurization is normal when doing an intake/leakdown test. It's the amount of pressurization/leakdown that you are concerned with. Too much signifies that you may have issues.

 

[ddavisaf]

Rotate the crank about 30 degrees and try again. It's quite possible you're experiencing valve overlap.
If this doesn't help, I suggest running a compression and leakdown test.

 

[seefour]

Sean, I guess no matter where I post your always gonna be able to help me out. haha.

Yeah, I was afraid of the other possibilities that could cause this. I'm gonna get ahold of a compression gauge tomorrow and see how that goes.

Thanks guys,
-Nick

EDIT: I forgot to add I tried rotating the crank several times. Wouldnt that cause the air to go out the exhaust and not into the crankcase?

 

[ddavisaf]

If you rotate it to the correct position then it will keep the air in the intake track. More or less. It's closing the intake valves and keeping the air in the manifold, which for intake testing is what you want. If you get alot of air in the crankcase regardless of the position of the crank, it's possible you have a bent valve, a chipped valve, bad valve seals, etc. (worst case scenario)
As Sean said, your rings may be worn as well.
Also, make sure you take your mbc out of the system when testing for boost leaks.
And you mentioned a catch can. Did you replace the PVC with a 1/8" NPC straight fitting?

 

[seefour]

I have the hose to the catch can coming right off the vent on the valve cover. I left the stock PCV in place to help out at idle.

 

[seefour]

compression was as follows:

150 150 150 140 with #1 being the lowest.

 

[1SloColt]

Rotate the crank about 30 degrees and try again. It's quite possible you're experiencing valve overlap.

Or put the motor at top dead center.

 

[seefour]

I was afraid that i let the motor cool down to much when i did the compression test so i retried after I just turned it off and I got: 150 all across the board.

Then, I made sure the motor was at top dead center and boost leak tested again with the same results.

So, I'm thinking its the valve stem seals...

 

[1fast97gsx]

Do a wet compression test.

 

[burntheblobs]

No need for a wet test. That is good compression for a 1g. Im pretty sure 165 is perfect while 121 is the service limit.