SwedeSpeed - Volvo Performance Forum banner
1 - 16 of 16 Posts

·
Registered
Joined
·
366 Posts
Discussion Starter · #1 ·
So, i've been chasing a funky oil leak at the big front PCV block vent. As in the large flange on the front of the block that connects to the flame trap.

I've done just about everything for diagnosis and have yet to figure this out. Oil keeps oozing out from the front block vent to hose connection. Happens especially when cruising on the highway.

Does anybody have a cutaway or a blueprint of the block???

I was thinking, maybe liquid oil is backing up to the block vent to hose connection, then draining through the flame trap and back to the pan?? Obviously, the flange is only designed to contain oil vapors. Anybody know where that front upper block vent leads to???? Maybe somewhere downstream of the front block vent is partially occluded and eventually causes a backup/spill over at the front block vent?

My mechanic test drove the car for 30 mi around town and it didn't leak a drop, but once i picked the car up and drove 40 mi home on the highway, it leaked almost immediately. Perhaps continuous oil pressure causes a backup, yet around town driving allows for enough internal drainage to not be a problem?
 

·
Registered
Joined
·
2,368 Posts
Are you certain of the source? Could it be a leaky cam cover or seal that is tracking down to that spot? Unless you have crazy high crankcase pressure (and blowing oil out elsewhere too), a flame trap full of oil or have turned the engine on its side, it doesn't make much sense. That should be a low pressure connection and not flowing oil.
 

·
Registered
Joined
·
17,419 Posts
Since I have never done this work, this is probably a stupid question, but could it be a cracked piece or a clamp of some sort at the connection point? It makes sense to me that continuous pressure would maybe leak and around town it's not enough to push the limit.
Perhaps continuous oil pressure causes a backup, yet around town driving allows for enough internal drainage to not be a problem?
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #4 ·
Absolutely positive on location of the leak. Definitely not a bad seal, clamp, or hose. ALL of the oil or oil vapor holding stuff above it is new. I've taken off the intake twice - there's no oil above the front block vent flange and it clearly is leaking at the flange to hose connection. There's plenty of negative vac at the valve cover at idle, maybe even too much, but i'm not sure how to tell if the flame trap to turbo intake hose is clear. It was new last year, so i'd argue that it's flowing. Dipstick never popped out when in boost and there's no leaks elsewhere. Potentially good PCV function.

Anybody know where the front upper block vent leads to??? How does it gather oil fumes??


Here's my list of potential causes:

Sludge near the front block vent -- cause liquid oil overflow
Blocked PCV to turbo inlet (unlikely)
Cracked block at the flange (unlikely - flange is HUGE)
Maybe a bad evap check valve?? Would lead to inconsistent loss of PCV vac and positive crank pressure??
 

·
Registered
Joined
·
9,228 Posts
u sure the 2 hoses on top of pcv box are hooked up correctly? one coming from upper cam cover goes further away from block and the one going to inlet pipe is closer to block.
 

·
Registered
Joined
·
1,396 Posts
+1 it seems you pressure is off kilter.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
144 Posts
Get some oil dye at autozone and get some oil dye and drive it. Then use a USB light to find the source. But you need to make sure everything is super clean first.

Sent from my SM-G955U1 using Tapatalk
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #9 ·
Just checked. Definitely PCV plumbed correctly. There is literally no way to screw that up. I think both hoses are too short to insert into opposing nipples.
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #10 ·
Care to elaborate on that?

Seems we're back to:
Sludge near the front block vent -- cause liquid oil overflow
Blocked PCV to turbo inlet (unlikely)
Cracked block at the flange (unlikely - flange is HUGE)
Maybe a bad evap check valve?? Would lead to inconsistent loss of PCV vac and positive crank pressure??
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #12 ·
Probably can't get a really good perspective without taking the intake off. It leaks from one single place - the front upper block vent to PCV hose junction. Since the flange isn't barbed, liquid oil simply slips out from under the hose. Usually, on most P2's, there will be about a tablespoon of liquid oil pooled at the face of the block vent and being held in by the aforementioned hose/clamp. Obviously, the system is designed to hold a little bit of oil there.

My theory is that I have liquid oil flowing through this passage at an extraordinary rate due to upstream sludge. Crazy? Plausible? Barking up the wrong tree?
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #13 ·
Had a thought today. How the heck would i clean out the oil passages even if i did pull the oil pan off????
Hypothetically, what if i do have a significant sludge obstruction somewhere that's causing this leak. How would i clear it without pulling the motor?

Perhaps take the pan off, then run a braided metal cable into whatever passages i find? Maybe fray the cable end so i get more grabbing action when i pull it through? Then... Dump some paint thinner or solvent in to wash the crap out?

Pretty sure this would dislodge crap, but it'd find its way into the oil passages for the bearings and then cause oil starvation, right???
 

·
Registered
Joined
·
144 Posts
Drain the oil. Run refill with 5qts atf 1qt oil and let idle for a couple of hours. The detergents in the atf will clean alot of the sludge. Drain it out then replace the filter and oil. Run synthetic.

Sent from my SM-G955U1 using Tapatalk
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #15 ·
With the decreased film strength or lessened magic motor oil properties of ATF, do i risk causing increased wear on the bearing/rings?
 

·
Registered
Joined
·
366 Posts
Discussion Starter · #16 ·
Oh yea, forgot to mention. I just engine flushed it twice with the Lubri Moly stuff. Obviously, that didn't fix things. Did come out black both times though. Perhaps there's some caked in sludge that can't be dissolved easily?
 
1 - 16 of 16 Posts
Top