High rpm crankcase pressure = oil pan leak
07-14-2011, 08:38 PM
#1
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High rpm crankcase pressure = oil pan leak I searched & I know it's been covered a lot, but the threads always seem to focus on 1) blown or high modded motors, or 2) oil in the intake.
I don't mind the stock 2004 LS6 pcv setup & I can live with cleaning the intake every so often.
I have zero oil leak with normal driving, but 1 day of autox competition & I have leaking at the bottom oil pan gasket. No it's not the main seal, front cover, crank position sensor, or oil galley plug, so don't go there. I did a cleanup/dye test.
The motor has not been apart, I don't think any hose is kinked or pinched.
Is there any way to relieve a bit more pressure on a stock engine/stock tune setup and not mess with tune/maf/fuel map all that?
I think the nature of an autox run with multiple wot/closed throttle applications x a dozen runs puts the engine crankcase thru extreme cycles of maximum vac/press, vac/press and just forces some oil past the gasket.
TIA
I don't mind the stock 2004 LS6 pcv setup & I can live with cleaning the intake every so often.
I have zero oil leak with normal driving, but 1 day of autox competition & I have leaking at the bottom oil pan gasket. No it's not the main seal, front cover, crank position sensor, or oil galley plug, so don't go there. I did a cleanup/dye test.
The motor has not been apart, I don't think any hose is kinked or pinched.
Is there any way to relieve a bit more pressure on a stock engine/stock tune setup and not mess with tune/maf/fuel map all that?
I think the nature of an autox run with multiple wot/closed throttle applications x a dozen runs puts the engine crankcase thru extreme cycles of maximum vac/press, vac/press and just forces some oil past the gasket.
TIA
07-15-2011, 12:33 AM
#4
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07-15-2011, 01:31 AM
#5
Get a valve cover breather that replaces the oil cap on the RH valve cover, and just install it for the autoX event only to see if that changes things or not.
07-15-2011, 12:42 PM
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Well first need to do a leak down test. To determine if excessive blow by. Fix any problems. If all good a vacuum pump would be best performance option. A open crank case is asking for problems if daily driver also. From contamination into your oil.
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07-15-2011, 06:49 PM
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07-15-2011, 06:52 PM
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Thanks
07-15-2011, 07:00 PM
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Hard to believe the crankcase would build up enough pressure to actually make the oil pan gasket leak. I would think the pressure would vent back through the fresh air hose on the PCV system first. Have you checked that hose for oil and also have you checked your intake tube before the throttle body for excess oil?
Get a valve cover breather that replaces the oil cap on the RH valve cover, and just install it for the autoX event only to see if that changes things or not.
Get a valve cover breather that replaces the oil cap on the RH valve cover, and just install it for the autoX event only to see if that changes things or not.
The hose has a nipple/bulge fit on the valley cover end but is just a slip fit on the TB (plastic) end, it's pretty easy to slip off/on & I can see where oily gas has leaked by, not wet oily but seepage.
There are 2 hoses into the tb. One from the valley cover & one from the pass side valve cover. Another vent on the driver side rocker (rear) is plugged off per factory.
If I put a clamp on the (slight) leaky pcv hose that would only serve to increase pressure, yes?
I do like the idea of venting the oil fill cap for racing, I actually have a spare cap I could drill & tap for a little screw on vent/filter. What would work there?
07-15-2011, 07:07 PM
#12
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I agree, do not want to run open.
Will venting the oil filler cap be considered a vacuum leak by the engine control/metering computer & throw codes?
07-15-2011, 07:12 PM
#14
Under WOT conditions, and if the engine is producing excess crank pressure due to high blow-by, then dirty crank gasses will flow from the engine down BOTH those hoses ... that's why the fresh air hose can get oil residue in it, and even puke oil into the intake duct before the TB.
You might want to check all the PCV hoses just to make sure there isn't something blocking or restricting them.
07-16-2011, 01:02 PM
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Yes ... the hose from the valley cover is the hose that goes to the manifold "high vacuum side" of the throttle butterfly. The other hose coming off the front of the passenger side valve cover is the "PCV fresh air make-up hose", with taps into the front side of the throttle butterfly, and only sees near ATM pressure inside the intake duct before the TB.
Under WOT conditions, and if the engine is producing excess crank pressure due to high blow-by, then dirty crank gasses will flow from the engine down BOTH those hoses ... that's why the fresh air hose can get oil residue in it, and even puke oil into the intake duct before the TB.
I doubt it would increase the pressure any, if at all. Like I said above, there is oil residue there because the crank gasses are back flowing down the fresh air hose.
Should work if the filter is big enough. I'd at least try the valve cover vent during an autocross or two to see if that cures the issue or not. If it does, then there is too much crankcase pressure (for some reason) for your stock PCV system to handle.
You might want to check all the PCV hoses just to make sure there isn't something blocking or restricting them.
Under WOT conditions, and if the engine is producing excess crank pressure due to high blow-by, then dirty crank gasses will flow from the engine down BOTH those hoses ... that's why the fresh air hose can get oil residue in it, and even puke oil into the intake duct before the TB.
I doubt it would increase the pressure any, if at all. Like I said above, there is oil residue there because the crank gasses are back flowing down the fresh air hose.
Should work if the filter is big enough. I'd at least try the valve cover vent during an autocross or two to see if that cures the issue or not. If it does, then there is too much crankcase pressure (for some reason) for your stock PCV system to handle.
You might want to check all the PCV hoses just to make sure there isn't something blocking or restricting them.
Thanks.
07-16-2011, 01:48 PM
#16
07-16-2011, 05:38 PM
#17
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Do you know if I vent the driver side valve cover and/or the oil filler cap, if that will mean a vacuum leak or unmetered air getting into the equation?
For unmetered air to mess up how the engine runs, I think it has to be into the intake. This would let air into the crankcase at low rpm vacuum stage & vent pressure from crankcase at high rpm pressure stage.
I'm a bit over my head here, but trying to understand the mechanics of it b4 I mess with it.
With 40k miles I would think I am getting more blowby every year & the stock pcv & stock seals on the motor are just giving up the battle a little bit.
07-16-2011, 05:49 PM
#18
Do you know if I vent the driver side valve cover and/or the oil filler cap, if that will mean a vacuum leak or unmetered air getting into the equation?
For unmetered air to mess up how the engine runs, I think it has to be into the intake. This would let air into the crankcase at low rpm vacuum stage & vent pressure from crankcase at high rpm pressure stage.
For unmetered air to mess up how the engine runs, I think it has to be into the intake. This would let air into the crankcase at low rpm vacuum stage & vent pressure from crankcase at high rpm pressure stage.
On the stock PCV setup, the fresh air hose is tapping off between the air flow sensor and the throttle body butterfly, so the mass of air that diverts down to the valve cover and through the crank and back to the intake manifold has been accounted for.
I think if you bought an open breather filter for the oil filler cap and popped it on before an autocross and took it off after (10 sec job), you'd never see the effects of the small amount of un-metered air because you're far from idling around an autocross course. This would also prevent any crankcase pressurization and seal leakage ... only way to find out is try it.
07-16-2011, 11:11 PM
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If you put a open breather on the oil filler neck on the passenger side valve cover, then you will be getting a little un-metered air. That is because the fresh air that is entering that open filter is going through the crankcase and then back out the PCV hose on the valley cover and into the intake manifold.
On the stock PCV setup, the fresh air hose is tapping off between the air flow sensor and the throttle body butterfly, so the mass of air that diverts down to the valve cover and through the crank and back to the intake manifold has been accounted for.
I think if you bought an open breather filter for the oil filler cap and popped it on before an autocross and took it off after (10 sec job), you'd never see the effects of the small amount of un-metered air because you're far from idling around an autocross course. This would also prevent any crankcase pressurization and seal leakage ... only way to find out is try it.
On the stock PCV setup, the fresh air hose is tapping off between the air flow sensor and the throttle body butterfly, so the mass of air that diverts down to the valve cover and through the crank and back to the intake manifold has been accounted for.
I think if you bought an open breather filter for the oil filler cap and popped it on before an autocross and took it off after (10 sec job), you'd never see the effects of the small amount of un-metered air because you're far from idling around an autocross course. This would also prevent any crankcase pressurization and seal leakage ... only way to find out is try it.
I was thinking som more about the short hose that runs from vallery cover to tb & even though it "looks" ok to me, it does have a SERIOUS 180 degree bend in it in a very short distance (say 6 inch hose). I wonder if 40k miles of heat cycles has narrowed down that ID measurement to something that is a restriction.
Maybe I can fab up a short hose with the 180 being metal tube of the same or better ID, but I don't know chit about bending tubing without crimping it.
2nd best is just get an oem hose there if I can find one.
07-17-2011, 02:14 AM
#20
Attached is a photo of the stock PCV hardware that come off my '02 Z06 when I installed an Elite Engineering oil catch can.
So you don't have that 180 degree piece that is made out of hard plastic? BTW ... the 2004 LSx engines don't have an actual PCV valve because there is a 2.5 mm (0.10") fixed orifice in the metal nipple coming off the valley cover. GM decided to get rid of the valve and use a fixed orifice to regulate the flow of crankcase gases.
Second photo shows the catch can installed. The hose coming off the front RH corner of the valley cover goes to the top nipple on the can, and the hose between the nipple coming off the side of the can and the intake manifold has the PCV valve in the rubber housing that is larger than the hose diameter. Again, your 2004 will not have a PCV valve due to the fixed orifice design.
The fresh air line goes from the front/top of the RH valve cover to the intake manifold (before the throttle butterfly).
So you don't have that 180 degree piece that is made out of hard plastic? BTW ... the 2004 LSx engines don't have an actual PCV valve because there is a 2.5 mm (0.10") fixed orifice in the metal nipple coming off the valley cover. GM decided to get rid of the valve and use a fixed orifice to regulate the flow of crankcase gases.
Second photo shows the catch can installed. The hose coming off the front RH corner of the valley cover goes to the top nipple on the can, and the hose between the nipple coming off the side of the can and the intake manifold has the PCV valve in the rubber housing that is larger than the hose diameter. Again, your 2004 will not have a PCV valve due to the fixed orifice design.
The fresh air line goes from the front/top of the RH valve cover to the intake manifold (before the throttle butterfly).
Last edited by ZeeOSix; 07-17-2011 at 02:57 AM.