Putting a Stop to Oil Consumption through the PCV Valve

Discussion in 'Fox 5.0 Mustang Tech' started by vristang, May 19, 2006.

  1. Putting a Stop to Oil Consumption through the PCV Valve

    Background Info on the PCV System
    The PCV is an emissions device that allows the pressure and corrosive gasses in the crankcase to vent, without venting these harmful gasses to the environment. The directional valve is in place to prevent a backfire from spreading to the crankcase. In the event of a backfire into the intake manifold, the PCV is supposed to seal shut, preventing the flame front from traveling into the crankcase. Without this directional valve in place (and fully functional) a backfire could also cause a crankcase explosion.
    All motors will experience some degree of Blowby. Even a freshly rebuilt motor can experience between 5-10% Blowby, as checked with a Leakdown test. (Blowby is not the only source of crankcase pressure however. Due to the reciprocation of the pistons there will be a build up of pressure due to the air not being able to flow as fast as the pistons are moving in the higher RPMs) Blowby of combustion gasses introduces fuel and other combustion by products into the crankcase. Raw fuel, moisture, and various acidic materials will all contaminate the engine oil. Moisture can also enter the crankcase due to condensation overnight.
    The good news is that most of these contaminants are highly volatile, meaning they will vaporize at relatively low temps; around 200F. Once these contaminants and moisture have volatized though, they must be purged from the crankcase. This is where a crankcase ventilation system comes in.
    In the old days the crankcase was vented to the atmosphere via a hose that ran under the car or into the exhaust. The downside to this is that these volatile materials were being introduced to the atmosphere, increasing environmental damage. Now a Positive Crankcase Ventilation system is in use. In a positive venting system the crankcase contaminants are purged into the intake manifold so that they can be burned in the normal combustion process. This is very effective at reducing the amount of unburned HCs that are released to the atmosphere.

    Troubleshooting Your Oil Control Issues
    The first step is to find out where the oil is coming from.
    Pull the Throttle Body/Valve Cover hose from the TB. If it is wet with oil then this is an entry point. The normal causes of this are excess Blowby (which needs to be ruled out with a compression test), or the VC baffle has been removed for rocker clearance. Just looking down the oil filler neck should reveal if the baffle is in place. If you see rockers, then it is time to get creative and fabricate a baffle. If there is no baffle but the TB/VC hose is bone dry then you may be able to get away without using a baffle.
    Next pull the PCV hose. Again if it is wet with oil, this is an entry route. A quick fix for this is a separator from Steeda, Home Depot, or Lowes. For about $25 (The Steeda unit will be more expensive) for the separator and fittings you will be able to remove most of the oil before it gets to the intake.
    Also, you need to verify that the PCV screen is in place. This often forgotten part is located underneath the PCV in the back of the intake, and helps remove oil mist from the crankcase gasses.

    Contributed by tmoss... www.tmossporting.com
    I have seen a BUNCH of intakes (100s) and you can tell the lower intakes that were on cars whose PCV screen had been blocked - they have a very thick coat of grime on the bottom of the lower intake. You know the heads had a nice thick coat below the rockers too as the blow-by had no where to go. When you put the intake in a solvent tank and wash it, it does not cut all the crud off - reason? - the blowby gasses will not come off with safety solvent. why, I don't know.
    Do your self a BIG favor and install a PCV screen once a year.

    If a compression test comes back normal, and the above mentioned lines are dry, then the valve guides are suspect.

    The PCV Problem
    Many of the Fox Body Mustangs seem to have serious issues with oil consumption through the PCV or Throttle Body/Valve Cover line. There are 3 main causes of this problem.
    1. Excessive Blowby
    2. Removing the Valve Cover Baffle at the oil filler neck
    3. Removing the Baffle and/or the PCV Screen on the lower intake
    However, in some head/cam/intake (and possibly stroker) combinations the problem can persist.
    Sometimes a small oil/air separator can be used to help filter out the oil before it gets to the intake manifold. Most who run this setup will remove the small plastic filter, as it tends to plug up and restrict airflow. An oil/air separator is a band-aid solution though, and should not be considered permanent. The goal should be to completely eliminate the flow of oil from the crankcase.

    The problem seems to be that the stock PCV line does not flow enough volume to allow adequate ventilation in modified motors. The lack of volume flow creates a build up of pressure in the crankcase which forces crankcase gasses through the PCV at higher velocities. With the added velocity the crankcase gasses are able to pick up more oil vapor; carrying it into the intake manifold.
    Yet another issue is that the stock single PCV system can create rather long flow paths for pressure to vent. For example gasses in the front of the crankcase would have to flow to the back of the block to exit through the stock PCV. The result of a long flow path is that it will take longer to purge the crankcase pressure.

    The solution is to allow a greater volume of gasses to vent from the crankcase, at lower velocities. This can be done with a larger ID PCV hose and PCV, or by adding a second PCV line. Since larger ID PCV valves can be hard to find the easiest solution should be to add a second PCV line to the drivers side valve cover.
    The stock drivers’ side valve cover can be replaced with any valve cover that has an oil filler/breather hole. What valve cover is used does not matter, so long as there is a way to mount a PCV valve to the valve cover. A stock passenger side valve cover installed on the drivers’ side would work well, or many of the aftermarket valve covers have holes intended for mounting breather caps.
    The hose from your new PCV should flow either directly to the intake manifold (parallel to the stock hose), or merge with the stock hose. An air compressor oil/air separator can still be used to filter out any oil that does get out of the crankcase. However, if the system is setup right and the motor is healthy, there should be very little oil accumulation in the separator if any at all.

    Secondary Benefits
    The increase in the volume of air that can flow out of the crankcase means lower accumulations of harmful Blowby gasses and moisture. Also, lower crankcase pressures will allow greater efficiency and power (although this affect is probably minimal on a street car).

    More Notes on Installation
    1. It may be better to install the drivers side valve cover PCV toward the front of the motor. This will allow a shorter path for gasses that are trapped in the front of the crankcase.
    2. It may not be a good idea to install a third PCV on the aft side of the passenger side valve cover, as this could allow fresh air from the TB/VC hose to vent directly out that PCV. This would result in no fresh air hitting the crankcase, and a greater accumulation of harmful crankcase gasses and moisture.

    Extra Notes
    From what I have seen, the oil accumulation in the intake will be greatest when the car is left to idle for some time (stuck in traffic or idling in the driveway), and then with some rpm the oil is picked up and thrown into the combustion chamber. If you live in a humid part of the country, or see a fair amount of condensation on the ground in the morning, then you will most likely notice some moisture in the separator, resulting in the easily recognized brown milkshake appearance of the oil in the separator. This is fairly normal, as overnight condensation will form on the inside of the engine block. Once the oil gets up to temperature, this moisture boils off, and collects in the separator.

    This is a picture I took of my engine at its worst. The car had been at idle for several minutes before I shut it off.

    This is a picture of my current setup.

    Hope this helps some,

    Home Depot
    Fram PCV Screen - # BA8113
    NAPA PCV Screen - # 6978
    Napa PCV - # MPF39203 / CRB29203
    Fram PCV - # FV198
    Purolator PCV- # PV98C
    Borg Warner PCV- # PCV203
  2. I will be revising the above to include my previous writeup on installing an oil/air separator, but wanted to get some feedback from all the smart folks here as well.

    EDIT: It has been revised.

    If you have any thoughts that should be added or find any errors please let me know.

  3. how about two pcv's if one isn't enough?
  4. i just put an oil separator in between the intake manifold and the pcv about 3-4 weeks ago and i dont have a drop of oil in my intake. and i just made 6 pulls on the dyno (when blowby is at its worst) with no oil getting into the manifold.
  5. this should become a sticky
  6. The separators are great, and I don't want to take away from their effectiveness.
    For my application however, a separator was nowhere near enough.

    How often do you empty out your separator?

    Before I added the second PCV valve I was dumping my separator atleast every fillup; ~200miles.
    That was far too much oil for my taste.
    Also, it seems that once the separators are about 1/2 full, they no longer accumulate oil. At that point oil is allowed to pass into the intake.

    Now, I may be able to remove the separator, but I will give it more time to make sure I don't have any other issues.
    I have been using this for about 2 weeks now.

  7. i got a prob rightnow its my 99 cobra uses oil bad 6 qts in 1000 miles it dont smoke if i dont run it hard ,,but if a dog on it ,it smokes like james bond cars do..my comp. is good my leakdown is good ,,if i rev car to say 4grand for 30 seconds it billows out the back bad ,im to the point of no return .with pulling motor out.pass side plugs 1,2,4 and 5 got oil dep on them ,the drivers side head gasket is leaking by the front cover ,the oil sep wont help me any ..i heard that the wrong seals where installed at the factory?? i dunno. i heard stories of 03/04 cobras smoking to with 10,000 miles on them ..
  8. sound like it's time for a rebuild
  9. I have seen a BUNCH of intakes (100s) and you can tell the lower intakes that were on cars whose PCV screen had been blocked - they have a very thick coat of grime on the bottom of the lower intake. You know the heads had a nice thick coat below the rockers too as the blow-by had no where to go. When you put the intake in a solvent tank and wash it, it does not cut all the crud off - reason? - the blowby gasses will not come off with safety solvent. why, I don't know.

    Do your self a BIG favor and install a PVC screen once a year.
  10. i recently put a mr gasket fuel filter inline between the oil filler neck and the throttle body. today i installed an air / oil seperator and drove the car for quite a while afterwards. when i popped the hood to check the reservoir on the seperator, i found it was spotless. not even a drop of oil.

  11. i empty it every 2-3 weeks

  12. your lower intake manifold gaskets are wigglin around on you. It happens a lot on 5.0's with aluminum heads, the fel-pro 1250 doesn't really stick well. that happened to me, except I sucked a ****load of coolant in. The mr. gasket equivelant of the 1250 adheres much better.
  13. would it be alright to just put a solid fitting in the intake and then just use a breather on each valve cover
  14. I am not sure I fully understand what you are proposing, but here is how I understand it.
    You want to plug the pcv oultet on the lower intake, put breather caps on the valve covers, and plug the TB/VC line.

    This would allow crankcase pressure to dissipate, but would not ventilate the crankcase as well as an active system (like stock).
    Pumping fresh air into the crankcase helps remove moisture and other pollutants from the crankcase.
    It would work, but is less than ideal.

    What you do not want to do is install breather caps on the valve covers, and leave the PCV valve in place. If using breathers that vent to the atmosphere the crankcase needs to be sealed off from the intake manifold. Otherwise, the intake manifold vacuum would be able to pull air from the atmosphere into the intake manifold. This air would not be metered by the MAF and would not be throttled by the TB. Essentially, this creates a vac leak.

  15. I was talking about a carbed application if makes any difference. That was what I did I just rebuilt my motor and I had lots of blowby. I tried an oil seperator but it filled up so damn fast like daily. So then I just bought 2 caps with the pcv holes and put the little k&n air filters in them. Now the motor doesn't seem quite as gutsy though
  16. a closed pcv system is better because of the vacuum in the crankcase. on my old motor, I had a bit of blowby, whenever I'd do a lot of racing, my pcv would pop out. I could tell the difference on the freeway. I'd first check my tire pressure, then feel back in the manifold to see if the pcv popped out again. anyways, breathers only vent when there is a lot of pressure in the crankcase, and at that point it doesn't relieve the pressure very much.
  17. On a 87GT N/A set up with 90K on the engine........would or should installing a one way check valve on the TB/VC line prevent oil from entering the intake through that route? Also what about using the larger Lightning PCV with a larger diameter hose to the intake to increase the flow of volume but reduce the velocity? I have had some leakage into the intake but after removing the baffle in the VC and doing a H/C/I swap the oil consumption is horrible. I would use maybe 1/2-1 quart every oil change (just drained noticed when draining.....never needed to add any prior to oil change). Now whenever I get after it from a slow speed or stop it's like a Toyota with 300K on it except mine sounds bad ass :nice: . Should I use the oil seperator on the PCV line or try the route mentioned above or both? I did install a one way check valve in the TB to VC line tonight but need to run it to see any improvement as I'm sure there is some leftover oil in the intake. Or is the extra PCV in the drivers side cover "THE" fix? I know there are 100 options out there but I would like to keep it easy and looking close to stock.
  18. Make sure that the check valve on the TB/VC line is going the right direction. (I'm sure you already did though)

    Where does most of the oil seem to be coming from?
    The PCV line or the TB/VC line?

    If you are getting oil through the TB/VC line, then the best option is to install an oil baffle. Some creative hammer work on a thin piece of Aluminum yielded me a nice little baffle, which I then bonded in place with JBWeld. I know welding would have been much better, but I lack the skills. The JBWeld has held up quite well for the last year or so.

    A separator on the PCV hose can help you determine if the problem is the PCV line or not. The PCV is supposed to be a directional valve, so in theory another check valve on this line would be useless. (I doubt the ability of the PCV to seal however, as most people running boost seem to have issues with pressurizing the crankcase)
    After making a change as you have I would use some TB cleaner to speed up the process of cleaning the intake.
    Make sure that the lower intake had a baffle installed under the PCV, and that the PCV Screen is in place. It is common to overlook these items with an intake swap.

    Hope you get it sorted out.

    What ever method you try, please come back and let us know how it works for you.


  19. TB to VC is really wet and the check valve flows from the TB to the VC stopping flow from the VC to the TB/Intake. I haven't looked at the PCV line much yet but headed there. Something I never really looked at was to see if the Trickflow intake had a baffle below the PCV. The intake was used by someone else but for only a month and he went to a blower. I do have the screen, grommet, PCV all in place though. Also if I did a seperator set up would the higher one be better?

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  20. Now that I have thought about it, some feel that the TB/VC line needs to be bi-directional. The thought is that if flow is maxed out at the PCV, pressure can still vent via the TB/VC line. For example high crankcase pressure and low intake vac. I am still undecided on this though. A baffle is by far the best solution for oil flow through this line, and it is likely that it will solve the oil problem on this line.

    Home Depot does offer 2 separators. The larger one is probably overkill. I did purchase one, but never got a round to installing it. I didn't even know where to put that monster anyway.