Crankcase Pressure Issues
Teching In
Joined: Mar 2013
Posts: 48
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From: SE of Pittsburgh, PA
Which breather? Some have a check valve to allow air only into the engine, another has a check valve to vent excess pressure from the engine and others have no check valve, so it flows either way. You have excessive pressure in your crankcase. How does it happen? Not being able to vent the vapors or a pcv system that can not handle the amount of vapors generated. Seal off your oil cap and remove your fresh air makeup hose. You should feel a vacuum on the hose going to the engine. If your allowing fresh air to only enter through the breather, then a slight vacuum should be present with the breather removed. If too much blow by, may be piston to wall clearance and ring/gap issues at wot. Or some how cylinder pressure is getting into an oil return passage through the head gasket. Or an exhaust restriction is allowing pressure to be applied to the exhaust valve guide and seal area. Long shots, but crankcase pressure has to be coming from somewhere.
Teching In
Joined: Mar 2013
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From: SE of Pittsburgh, PA
This does not seem correct. Need to block off the stock fresh air makeup to the engine. It will not develop much vacuum with allowing fresh air to enter the engine. Regardless, 20 psi in a stock or any engine can not be correct. Vacuum is messured in inches of mercury. Should be around 15-18 inches of mercury. 20 psi in the crankcase, would be big issues.
TECH Addict
Joined: Mar 2013
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This does not seem correct. Need to block off the stock fresh air makeup to the engine. It will not develop much vacuum with allowing fresh air to enter the engine. Regardless, 20 psi in a stock or any engine can not be correct. Vacuum is messured in inches of mercury. Should be around 15-18 inches of mercury. 20 psi in the crankcase, would be big issues.
Teching In
Joined: Mar 2013
Posts: 48
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From: SE of Pittsburgh, PA
TECH Addict
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Nothing is sealed in the crankcase. The pcv system works by pulling fresh air in AFTER the MAF so the computer knows how much air is entering the engine. Then it get pulled across the crankcase by engine vacuum in the intake manifold.
The PCV valve meters this action, in normal conditions at idle crankcase pressure will be a slight vacuum. As you increase rpms and crankcase pressure increases it has to go someplace. It is designed that if crankcase pressure goes high it gets pulled into the engine through the PCV system inlet after the MAF.
He is exceeding the amount of pressure the PCV system can handle through the PCV inlet hose and PCV valve. this causes seals to leak or pop out and the dip stick to push out.
He must be building ALOT of pressure, something is very wrong with his piston-ring setup.
The PCV valve meters this action, in normal conditions at idle crankcase pressure will be a slight vacuum. As you increase rpms and crankcase pressure increases it has to go someplace. It is designed that if crankcase pressure goes high it gets pulled into the engine through the PCV system inlet after the MAF.
He is exceeding the amount of pressure the PCV system can handle through the PCV inlet hose and PCV valve. this causes seals to leak or pop out and the dip stick to push out.
He must be building ALOT of pressure, something is very wrong with his piston-ring setup.
Registered User
Joined: Nov 2014
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From: Arizona
Sorry typo in was inches
Mine pulls 12in car in thread
Stock pulls 20in woodys
Built pulls 17in top gear MS race car
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Verdad Gallardo Registered User
Joined: Nov 2014
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From: Arizona
What is the proper way to do a leak down test? Best practices please
Should motor be Hot? Cold?
Same with compression. Should the air compressor be regulated to motor compression psi? How would you know motor compression?
Should motor be Hot? Cold?
Same with compression. Should the air compressor be regulated to motor compression psi? How would you know motor compression?
Teching In
Joined: Mar 2013
Posts: 48
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From: SE of Pittsburgh, PA
That was for the cap. But how about the breather? Does it have a check valve? If so, which way? I prefer the one with a check valve that vents to the atmosphere if too much crankcase pressure. It will not solve your pressure issue but it may eliminate blowing the rear main seal. The idea of the check valve is not to allow unmetered air into the engine.
Registered User
Joined: Nov 2014
Posts: 38
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From: Arizona
That was for the cap. But how about the breather? Does it have a check valve? If so, which way? I prefer the one with a check valve that vents to the atmosphere if too much crankcase pressure. It will not solve your pressure issue but it may eliminate blowing the rear main seal. The idea of the check valve is not to allow unmetered air into the engine.
Teching In
Joined: Mar 2013
Posts: 48
Likes: 0
From: SE of Pittsburgh, PA
Nothing is sealed in the crankcase. The pcv system works by pulling fresh air in AFTER the MAF so the computer knows how much air is entering the engine. Then it get pulled across the crankcase by engine vacuum in the intake manifold.
The PCV valve meters this action, in normal conditions at idle crankcase pressure will be a slight vacuum. As you increase rpms and crankcase pressure increases it has to go someplace. It is designed that if crankcase pressure goes high it gets pulled into the engine through the PCV system inlet after the MAF.
He is exceeding the amount of pressure the PCV system can handle through the PCV inlet hose and PCV valve. this causes seals to leak or pop out and the dip stick to push out.
He must be building ALOT of pressure, something is very wrong with his piston-ring setup.
The PCV valve meters this action, in normal conditions at idle crankcase pressure will be a slight vacuum. As you increase rpms and crankcase pressure increases it has to go someplace. It is designed that if crankcase pressure goes high it gets pulled into the engine through the PCV system inlet after the MAF.
He is exceeding the amount of pressure the PCV system can handle through the PCV inlet hose and PCV valve. this causes seals to leak or pop out and the dip stick to push out.
He must be building ALOT of pressure, something is very wrong with his piston-ring setup.
Teching In
Joined: Mar 2013
Posts: 48
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From: SE of Pittsburgh, PA
Sorry, thought you had a breather. I got lost in the thread with the names. I believe the Hawks breather does not have a check valve. Therefore it can let unmetered air into your system and possibly cause idle hunting and the fuel trims to be off slightly. Which can be mostly corrected if your able to have it tuned. CFM Performance has a breather with a check valve that opens and vents if there is too much pressure.
Registered User
Joined: Nov 2014
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From: Arizona
We really dont know if oil blows out the exhaust. At idle we know there is no smoke. Even just driving to work. The only time anything happens its goin hard in the high RPMs at around 80-90mph and shifting from 2nd to 3rd gear. Seems that load magically changes the motor.
Now we know it blows oil all over. The headers are stained and oil drips from weep hole between bell housing and transmission. There is a tone of smoke that fills the air. Chalked up to oil hitting the hot headers. No idea if the smoke is blow by too. Hard to say.. The car has been nicknamed spy hunter do to the smoke screen it creates. Took o2 sensors out and they have carbon dust but still shiney. On back side
Like noted plugs are dry look new minus carbon
Now we know it blows oil all over. The headers are stained and oil drips from weep hole between bell housing and transmission. There is a tone of smoke that fills the air. Chalked up to oil hitting the hot headers. No idea if the smoke is blow by too. Hard to say.. The car has been nicknamed spy hunter do to the smoke screen it creates. Took o2 sensors out and they have carbon dust but still shiney. On back side
Like noted plugs are dry look new minus carbon
Registered User
Joined: Nov 2014
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From: Arizona
Vacuum at intake manifold 12"
When revving motor with gauge in intake manifold the gauge goes to 20"
Connected hoses back up then measured the vacuum at the back of both valve covers from the jumper hose that goes to catch can and I read zero
I checked in the top part of catch can and it matches the intake manifold of 12" which it should. I then bypassed the CC checked rear of valve covers still zero. I checked to make sure check valve was working at the connection by intake manifold by spraying air from rear hoses and I got a steady stream of air.
when testing valve cover hoses to catch can I read zero whether I'm reving or idle
Measured TB return reads zero. When reving motor I feel air Flo from valve cover but no vacuum.
When revving motor with gauge in intake manifold the gauge goes to 20"
Connected hoses back up then measured the vacuum at the back of both valve covers from the jumper hose that goes to catch can and I read zero
I checked in the top part of catch can and it matches the intake manifold of 12" which it should. I then bypassed the CC checked rear of valve covers still zero. I checked to make sure check valve was working at the connection by intake manifold by spraying air from rear hoses and I got a steady stream of air.
when testing valve cover hoses to catch can I read zero whether I'm reving or idle
Measured TB return reads zero. When reving motor I feel air Flo from valve cover but no vacuum.
Registered User
Joined: Nov 2014
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From: Arizona
I removed hose from the TB return and put it on the vacuum of intake manifold and that bad boy sucks like hell all the way I have vacuum at the back F both valve covers. Is the check valve needed? Is it causing the issue
Registered User
Joined: Nov 2014
Posts: 38
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From: Arizona
Registered User
Joined: Nov 2014
Posts: 38
Likes: 0
From: Arizona
Do I need check valve on the PCV side of things? I have great vacuum if I take the Vacuum port on the Intake manifold and install on the fresh air port on valve cover. then the vacuum at the driver side rear valve cover actually matches the 12"
is it possible that 12" of vacuum isn't good enough for check valve to function properly?
Registered User
Joined: Nov 2014
Posts: 38
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From: Arizona
What do you think is going on with the gaskets? Right now I pull no vacuum on the backside of the PCV valve. If I remove valve and hook back up it seems to work fine. I'm wondering if the valave is needed. Or can it be removed and I connect hoses straight through?