Crankcase pressure ventilation

[trixdout]

Seems to me like my GN has excessive crankcase pressure. Even my kn breather filters are getting super dirty from the inside of oil. They went from red to a very dark brick red, on the verge of brown.

Secondly, after taking utmost care in replacing the oil pan gasket this most recent time, it still leaks. The valve covers do not leak. Oil pressure is over 40psi at hot idle. Seems to me like the motor was rebuilt. In that respect, if and when I open up the part of the engine where the stock oil filter goes to see the gears, what should look like? Anything I can do there to lower the pressure a bit?

If I can't fix the pressure that way, can I tap the oil pan put a -4an host an connect it to the valve cover on the drivers side to relieve the pressure? Thinking that will cause any pressure to route to the valve cover which has a breather that is not clogged. Also on both sides the valve cover breather grommets are opened up enough.


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[earlbrown]

you can put a thicker gasket or stack another one under the 1" nut on the filter adapter to lower the oil pressure. That being said, MAKE SURE you have plenty of oil pressure at WOT if you go that route.

You can also run thinner oil if you're currently running something like 20w/50. It also wouldn't be a bad idea to verify your pressure gauge is accurate. (This may sound silly but does it read exactly 0 when the engine is off?)

All that being said, crankcase pressure and oil pressure are two completely different animals. The oil pump only pressurizes bearing clearances. Crankcase pressure comes form leakage between the rings and cylinder walls.

 

[robzombie]

You mean something like this. I know the pics suck, but you get the idea.

I had the pan down to fix the leak for the third time in as many months,this time I used [great stuff] only and no pan gasket. I only did it this way because that's what I had in my shop.

So far no more leaks and I'm happy and I get no oil out of the breathers or the line that I ran up under the M/C.

I don't know which one is responsible for eliminating the leak but it's not leaking and I'm happy.

 

[trixdout]

you can put a thicker gasket or stack another one under the 1" nut on the filter adapter to lower the oil pressure. That being said, MAKE SURE you have plenty of oil pressure at WOT if you go that route.

You can also run thinner oil if you're currently running something like 20w/50. It also wouldn't be a bad idea to verify your pressure gauge is accurate. (This may sound silly but does it read exactly 0 when the engine is off?)

All that being said, crankcase pressure and oil pressure are two completely different animals. The oil pump only pressurizes bearing clearances. Crankcase pressure comes form leakage between the rings and cylinder walls.

Well that explains a lot. So hmm. Not a pleasant set of information about the exhaust gasses leaking past the rings and pistons.

I have another question. What should be the ideal pressure in the crankcase? Like is there a specific number?




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[trixdout]

You mean something like this. I know the pics suck, but you get the idea.

I had the pan down to fix the leak for the third time in as many months,this time I used [great stuff] only and no pan gasket. I only did it this way because that's what I had in my shop.

So far no more leaks and I'm happy and I get no oil out of the breathers or the line that I ran up under the M/C.

I don't know which one is responsible for eliminating the leak but it's not leaking and I'm happy.

Rob, yea I saw your thread and asked you about that. I'm debating what to do.


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[robzombie]

My motor only has 5,000 miles on it, I hope it's not excessive blowby that caused my leaks.

I was thinking/hoping it was the windage in the crankcase that might be causing the leaks.

My oil never smells like raw fuel when I change it so I leaned more towards other reasons for the leaks.

 

[robzombie]

Rob, yea I saw your thread and asked you about that. I'm debating what to do.

Yea I remember now that you asked about it.

I hope that whatever you do, you find the solution as I know that oil leaks can be a big PIA and embarrassing when your car is always marking it's territory.

 

[trixdout]

Yea I remember now that you asked about it.

I hope that whatever you do, you find the solution as I know that oil leaks can be a big PIA and embarrassing when your car is always marking it's territory.

Yea i hope so too. I don't have money for a engine rebuild. At that point I might as well build a new motor and worry about the numbers matching one when its on the side.

 

[TurboBuRick]

They all have blow by in boost. Perfectly normal.

Make sure breathers and grommets are wide open.

To get rid of oil out the breathers you would run a catch can system.

HTH

Rick

 

[trixdout]

They all have blow by in boost. Perfectly normal.

Make sure breathers and grommets are wide open.

To get rid of oil out the breathers you would run a catch can system.

HTH

Rick

Alright sounds good. At least that aspect of the engine is good. I'm going to double check my pcv and see if its working properly.

 

[TurboBuRick]

Yes make sure it only lets air through 1 way. It should seal shut the other way like a check valve.

 

[robzombie]

I've been told not to run the pcv valve and I haven't had any problems so far. Is there a down side to not running it, I really don't want to suck oil into the intake and increase the likelihood of detonation or gunk up the intake.

 

[earlbrown]

The ECM is expecting a vacuum leak from the PCV. When you plug it, that messes with the calibrations in the fueling.

If you're blowing raw oil past the valley pan all the way to the PCV valve, you've got more problems than potential detonation.

 

[robzombie]

The ECM is expecting a vacuum leak from the PCV. When you plug it, that messes with the calibrations in the fueling.

^^^I've never heard of that.^^^

I've run it both ways and there wasn't any difference in the way the car ran, so I unhooked it again and will leave it that way so no oil/vapor will get in the intake.

If you're blowing raw oil past the valley pan all the way to the PCV valve, you've got more problems than potential detonation.

I wasn't sucking oil, I just know that if you run the pcv you will end up with gunk in the intake over time, so until someone can prove that it's needed I'll leave it unhooked.

Besides it's a shit system that doesn't work properly and with the right pcv so hard to find it's not worth it to me and when you do find the right one it's a crap shoot on how long it will last.