Problems,crankcase pressure
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Instructor
Joined: Apr 2006
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From: wakefield uk
Problems,crankcase pressure
It started with a little oil coming from dipstick tube,but now after sealing valve covers and distributor,I've now got oil coming from the join between engine and bellhousing at top.it's a 1980 auto with a turbocharger, 20,000 miles, things only get real bad at wot full boost.PCV valve appears clean , clear and working (up to a point).
whats going on!
whats going on!
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Originally Posted by turbovette80
It started with a little oil coming from dipstick tube,but now after sealing valve covers and distributor,I've now got oil coming from the join between engine and bellhousing at top.it's a 1980 auto with a turbocharger, 20,000 miles, things only get real bad at wot full boost.PCV valve appears clean , clear and working (up to a point).
whats going on!
whats going on!
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Not sure what a turbo does to the pressure inside the motor but the leak you are describing is a common leak at the back of the intake manifiold in the valley, the RTV bead ( if that's what you used to seal it ) can get blown out and leak down onto the bellhousing 
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
Hmm, never really thought about this, but on a turbo or supercharged motor your pressurising the intake right? so, then it follows that the vacume ports would get pressurised along with all the vacume operated stuff?
How does that work?
How does that work?
Thread Starter
Instructor
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From: wakefield uk
Originally Posted by Blue 2006
REPLY: Sounds like maybe a rear main seal . Excessive blowby gasses are the usual culprit . Are you running a high volume oil pump by chance ? I was on my 1970 Big Block after an engine buildup and was constantly leaking oil thru the rms until i went back to a normal volume pump plus i abandoned the PVC system altogether and went with positive crankcase evacuation thru the exhaust headers ; this system works very well. Havent had any leaks at all and doesnt use up any oil between changes.
Burning Brakes
Joined: Aug 2005
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From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by turbovette80
how does that work? The rtv seal at the back of the intake is dry the oil is coming from the join between the engine and gearbox all the the way round the bellhousing.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
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From: Carmichael CA
Originally Posted by SIXFOOTER
Hmm, never really thought about this, but on a turbo or supercharged motor your pressurising the intake right? so, then it follows that the vacume ports would get pressurised along with all the vacume operated stuff?
How does that work?
How does that work?
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Thread Starter
Instructor
Joined: Apr 2006
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From: wakefield uk
still need some help on this one,can't go with header evacuation,turbo plumbing makes it tricky,not to mention oil mist hitting the turbine. got to find a way to stop this oil getting out ,starter motor looks like its been dipped in 20-50w!!
help please
help please
Racer
Joined: Aug 2001
Posts: 445
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From: Austin Texas
I forget what it is called, but don't they make a vacuum pump that mounts to the front of the motor and suctions out all of the crankcase pressure? It is supposed to get rid of all kinds of oil seeping issues and free up some HP in the higher RPMs.
Have you considered that?
Bryan?
Have you considered that?
Bryan?
Burning Brakes
Joined: Nov 2004
Posts: 899
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From: Kansas
Have you put a compression test on it ,if not do so,
Remove plugs and install guage take out coil wire crank engine over check reading on all cylinders,compare readings to see if one cylinder is bad then squirt about a teaspoon of motor oil in each cylinder retest.
see if there is a big jump in pressure with oil that should tell if you got blowby thru the rings,or you could just have a bad rear seal,did you check to see if its not coming out of rear of intake manifold.
Remove plugs and install guage take out coil wire crank engine over check reading on all cylinders,compare readings to see if one cylinder is bad then squirt about a teaspoon of motor oil in each cylinder retest.
see if there is a big jump in pressure with oil that should tell if you got blowby thru the rings,or you could just have a bad rear seal,did you check to see if its not coming out of rear of intake manifold.
Safety Car
Joined: Nov 2002
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From: out of nowhere
Originally Posted by 300ZXTwinTurbo
I forget what it is called, but don't they make a vacuum pump that mounts to the front of the motor and suctions out all of the crankcase pressure? It is supposed to get rid of all kinds of oil seeping issues and free up some HP in the higher RPMs.
Have you considered that?
Bryan?
Have you considered that?
Bryan?
I've been told that as much evacuation as you can get is a good thing. I just bought all the AN stuff to run a line out the back of each of my valve covers.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
Originally Posted by Rockn-Roll
All vacuum lines must be routed to the carburator which sits on top of the blower. Maybe there is a vacuum line still attached to the intake manifold, or PCV is just not getting enough vacuum at WOT to keep the pressures down.
Race Director
Joined: Dec 1999
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You could install a vacuum pump but they are very expensive. With a turbo motor or any blown application you're always going to haev a little more blowby but yours sounds excessive. Do you have large breathers on your valve covers?
It could also be something very simple, someone may have used those end rail gaskets between the block and manifold, those things are very prone to leaking.
It could also be something very simple, someone may have used those end rail gaskets between the block and manifold, those things are very prone to leaking.
Melting Slicks
Joined: Feb 2001
Posts: 3,330
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From: Europe , Luxembourg
Hi
If the intake rear seal area is dry, I suggest you check the inside of your ignition ditributor. If this is oil wettened, the oil finds its way out through the ignition cable hole on the bottom of the ditributor dripping onto the bellhousing.
That's where my leak is from.
I plan a overhaul of the ditributor.
How does positive crankcase ventilation work into the exhaust ? Do you just route the valave cover line directly into the exhaust ?
Do you keep some kind of a check valve to avoid blow back from the exhaust ?
Isn't the exhaust pressure higher , specially when you run noise dampeners ?
Günther
If the intake rear seal area is dry, I suggest you check the inside of your ignition ditributor. If this is oil wettened, the oil finds its way out through the ignition cable hole on the bottom of the ditributor dripping onto the bellhousing.
That's where my leak is from.
I plan a overhaul of the ditributor.
How does positive crankcase ventilation work into the exhaust ? Do you just route the valave cover line directly into the exhaust ?
Do you keep some kind of a check valve to avoid blow back from the exhaust ?
Isn't the exhaust pressure higher , specially when you run noise dampeners ?
Günther
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From: Aylesbury Buckinghamshire. UK
I just cured that very same thing on my " non-turbocharged " 1980. Had oil splashed all over passenger side of engine bay coming from the dipstick after spirited run. Check all compressions which were OK ( 139 - 146 ) Abandoned the psv valve for a straight pipe which made a difference. Then fitted Edelbrock elite covers with breathers and that cured it completely. Was losing a pint every 200 miles, now lose nowt.
Bob ( UK )
Bob ( UK )
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From: wakefield uk
Originally Posted by Buckman62
I just cured that very same thing on my " non-turbocharged " 1980. Had oil splashed all over passenger side of engine bay coming from the dipstick after spirited run. Check all compressions which were OK ( 139 - 146 ) Abandoned the psv valve for a straight pipe which made a difference. Then fitted Edelbrock elite covers with breathers and that cured it completely. Was losing a pint every 200 miles, now lose nowt.
Bob ( UK )
Bob ( UK )