Oil Blow By

[maximos]

So I've looked at other threads on here and I've done some research on Google but my curiosity isn't entirely satisfied. I understand the cause of Oil Blow By and I also understand how to isolate where it's coming from. The only thing I can't figure out is how to prevent the problem on my car. I recently installed an Air/Oil separator and I'm somewhat alarmed at how quickly it's filling up.

My oil pressure gauge is typically at the equivalent of 3/4 full on the gas tank which always struck me as odd, but now I feel could be a cause of the problem.

I know that it is coming the PCV and nowhere else. I recently installed a new Motorcraft PCV valve and new hoses in hopes that it would help, but nothing has changed. One important thing to note is that the vacuum line that usually come off of the oil fill neck on the passenger side valve cover was capped off when my EGR was removed last year. Could I route that somewhere to relieve some pressure? I have an unused vacuum nozzle at the back of my upper intake that could help.

 

[turbogt]

you can't rely on the oil pressure gauge.. as long as your motor is producing more than 6 psi of oil pressure, the gauge is on...

it doesn't actually read pressure, its just an on/off switch..

and a little excessive oil pressure still wouldn't be the cause of blow by... its just getting past the rings..

 

[revhead347]

That air oil seperator has nothing to do with blow by. That thing is going to collect oil regardless of how old your engine is.

Kurt

 

[maximos]

and a little excessive oil pressure still wouldn't be the cause of blow by... its just getting past the rings..

I've read numerous times that excessive blow by is caused by too much pressure in the crank case and that relieving that pressure will help to minimize blow by. I guess my biggest question was that if I run a vacuum line from the oil-fill neck to the upper intake will it help to reduce the pressure in the crankcase?

Also, thanks for the info about the oil pressure gauge simply being an on/off deal...I had no idea.

 

[toyman]

I've read numerous times that excessive blow by is caused by too much pressure in the crank case and that relieving that pressure will help to minimize blow by. I guess my biggest question was that if I run a vacuum line from the oil-fill neck to the upper intake will it help to reduce the pressure in the crankcase?

I don't think you want to do that. Your PCV does that already. There should be a hose from the oil-fill neck to the air intake tube already and while intended to allow the burning of upper engine oil vapors also provides a partial release of internal pressure. Blow by is not caused by too much pressure in the crank case. Rather too much pressure in the crankcase is caused by blow by. Blow by is the result of piston rings not sealing as they should thereby allowing combustion gases into the crankcase.

 

[revhead347]

I don't think you want to do that. Your PCV does that already. There should be a hose from the oil-fill neck to the air intake tube already and while intended to allow the burning of upper engine oil vapors also provides a partial release of internal pressure.

The hose that goes from the oil fill neck to the intake is the breather hose for the engine. It's the other side of the PCV system. The intake sucks air in through the PCV, and that hose brings filtered air into the crankcase to replace the air being sucked out.

Kurt

 

[maximos]

So there should be a hose connecting the oil fill neck to the upper intake?

 

[revhead347]

It goes from the oil filler neck to the rubber inlet hose.

Kurt

 

[Black95GTS]

Try a breather or two on the valve covers.

Adam