Boost leaking into crankcase ?

[Miles Frederick]

Hey all, after a couple of tries I finally managed to seal up my throttle body shaft seals.  Which has lead to discovering a new leak.

When pressure testing.  Regulator set to 17-18 psi, boost climbs to around 9.  Pull off the oil cap and can hear a leak loud and clear along with the smell of gas inside the valve cover area.

I suspected the pcv, but have disconnected and plugged it with no change.

Though maybe it could be purge control pressurizing the gas tank forcing fuel through the injectors ?  But have disconnected and plugged the vacuum line (at the throttle body) for it with no results.

Though maybe the fuel pressure regulator was leaking air into the fuel system forcing fuel through the injectors but have disconnected and plugged the vacuum line to it as well.

No compression gauge at the moment, but when running, vacuum at idle is around 20 - 21.  It's a 1G

Anyone seen this before ?  What could it be ?

Thanks

Miles

[Kimyee Lai]

If this is while presure testing, boost has been known to leak past the turbo oil seals and right into the crankcase.

[Miles Frederick]

Thanks for the suggestion..

I Just went out and checked for that.  Capped of at the upper ic before the bov.  Unfortunately it's still doing it.

What confuses me is why the smell of gas ?

[JamieSibley]

Sounds like dead rings.  If the rings are gone, fuel will get into the oil while running. And while doing the pressure test, air will leak past the rings, into the crankcase and bring gas fumes with it.

[Miles Frederick]

Thanks for the suggestions,

  I'll pickup a compression tester tommorow.  Hopefully it's not the case as it's a relatively fresh bottom end (about 30k).

When you pressure test you're intakes, do you line up top dead center, or whichever to ensure the valves are closed ?  On a healthy engine, does no air leak past the rings on a pressure test ?

[Kevin Standeven]

At ~20psi it should hold steady, no leaking past the rings. You don't need it at TDC either. Hope the compression test checks out ok :?

[Miles Frederick]

Well, it's bad news...  150 90 155 140

After adding a tablespoon of oil the #2 raised to 150, I believe this indicated the rings ?  

Should I try to get ahold of a leak down tester to further isolate, or does the wet test pretty much say it all ?

A few years ago, the timing belt went, and the engine was completely rebuilt using oem parts, new pistons, rings, bearings, etc.  So it's surprizing as it's never seen more that 13 psi.  I did have a rather serious leak through the throttle body shaft seals, could the rich under boost condition have led to the massive decline in the #2 ?  or would it have affected all cylinders equally ?

Also, I've had the check engine light flash on periodically at idle for a second or two, then immediately off.  Always off when driving.  Stored code is 41 (Injector Circuit).  Even though there was no noticable difference in how it runs when the check engine lights up, could this have something to do with the condition ?

What else should I be looking for as the possible cause ?

It's been about an hour, I just tested again and it's indicating 150.  How long does the extra oil (wet test) seal it off ?  Shouldn't it be leaking again by now ?

Just changed to synthetic last weak after a couple of years running regular 10w30,  could this have something to do with it ?  Should I switch back just in case ?

What's the best deal in town when it comes to a rebuilt block ? Unfortunately I'm on a tight budget this time...

Sorry for all the questions,

Miles

[Mike Schmid]

If you didn't run the motor between compression tests then the oil didn't go anywhere and it should be the same result.  What the oil does is act as a sealant of sorts on the rings during the compression test.  

Compression tests give a good quick heads up of what kind of shape the motor is in but a leak down test gives a much more accurate idea of what's wrong and where it is.  

A rich under boost condition shouldn't cause ring leakage... if it does we're all in trouble, hehe.  A lean out could burn a hole in a piston causing compression loss but you'd get no compression, not 90 psi.  A damaged ring land might cause a compression drop...

Do a leak down test to make certain you've got a problem then confirm it with a teardown and fix with a new motor or rebuild or whatever...