View Full Version : Installing oil seperator

07-09-2006, 07:42 AM
I am just about to install an oil seperator on my 99'. just want to get it right it is it only necessary to put the filter between the valve cover and the intake tube, with the flow going from valve cover to tube. and should this reduce the start up smoke. With the money spent on engine mods and repairs i dont want to take any more chances harming the motor.

07-09-2006, 10:09 AM
I got it on the 01 and it seems to have helped.


07-09-2006, 01:05 PM
The PCV system works at both valve covers. It is not exactly a one way flow. The only location there is flow reversal is throught the breather line connected to the intake pipe before the throttle body. However, there is more bias on the negative pressure side of the PCV line where it connects to the intake plenum so the flow is primarily through the PCV valve (In most cases this is typical). The air/ oil separator should be connected to the PCV line only and the direction of air flow (usually indicated on the body of the separator) should be in the direction of the intake plenum. As the crank case pressure builds up, the flow may reverse through the breather line and should not pose too much of an issue with a naturally aspirated motor since there will be more vacuum on the PCV side. Since the PCV system flows too much, the oil separator will reduce the flow to some extent. They do work and will reduce the amount of oil consumption from the PCV line but you need to monitor the fluid level in the catch canister so that it does not fill up too much which may result in increase pressure in the crank case.

However, when power adders are involved, the flow characteristics are quite different. Since the PCV valve is connected to the intake plenum after the throttle body, a roots type blower or even a twin screw blower on top of the motor with a boost-bypass valve will create a pressure build up in the upper plenum which will close the PCV valve and the flow will reverse throught the breather hose once the boost-bypass dumps the compressed air in the lower plenum to the upper plenum. This will cause a momentary surge in crank case pressure which will push out into the intake which is a good thing to have some sort of filter there so that any oil will not saturate the intake line. This will be far more different with a centrigugal type supercharger or turbo system since the entire intake before and after the throttle body is under boost. Once the pressure in the intake and crankcase equilizes the flow reverses and winds up in the breather line which will push oil out in the opposite direction. If you wind up with too much pressure in the crank case that will force oil into the combustion chamber by pusing it past the pistion rings.

07-10-2006, 06:33 AM
So the seperator actually is ment to go between the valve cover and the plenum on the drivers side ( my passenger side) of the engine, not between the valve cover and intake tube. This is the side of the motor that causes the smoke on start up?

07-11-2006, 06:36 AM
In just about all cases only one oil separator is needed and it connects between the PCV port on the upper intake plenum (on a 99/01 right below the snake on the cover of the intake plenum) and the PCV valve on the dirvers side head. The large tube that connects to the air inlet pipe (between the MAF housing and the throttle body) is the breather line which you probably do not have to worry about. Those that have installed oil separators there do not get any oil in them. Think of it this way. The hose on the passenger side head that connects to the front of the valve cover is the input side and the drivers side at the back of the valve cover is the output side. The oil trap needs to be on the output side (connected to the PCV valve).

The intended locations for the breather is on the passenger side and the PCV is on the dirvers side. The roles can be reversed if you use long enough lines but is not necessary.

The wall mart bought part (or even from Lowes hardware or Sears Hardware, or even from Home depot, do not come with a mounting plate so you may need to fabricate one. Then comes the thought on where to mount it. If there was more room then a Greedy PCV oil catch can could be used (typical with imports and turbo's) but they are far more expensive. JLT has a nifty one that just plugs in where it should be, between the valve cover and the PCV valve, what is nice about that part is that you do not have to dump the oil out. (see the same topic in the 03/04 area there is a link to the JLT part).

I used to have one on my 04 but decided to machine a part from 3" round aluminum stock I found at work. Plus I have the SHM filter for the breather side which seems to work for my application.