1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Oil leaks from valve cover? Anyone else?

Discussion in 'Intermediate CJ-5/6/7/8' started by Mugzilla, Sep 6, 2009.

  1. Sep 6, 2009
    Mugzilla

    Mugzilla Member

    Pompano Beach,...
    Joined:
    Jul 31, 2003
    Messages:
    203
    I have an aftermarket chrome valve cover. I know, I know, chrome dont get you home, but it was aquired 10 or so years ago, and the stock cover was ditched.

    On my 75 CJ-5 w/ a 258, I get a pretty decent amount of leaking oil on the driver's side into those little valleys over the exhaust header. I THINK this is why my Jeep smells so bad after shutdown! Anyone else have/had this problem?

    How did you solve your leaks? I do have a PCV valve, but after S/D, oil drips out. Obviously, the PCV is not the solution, since this is technically a vacuum leak.
     
  2. Sep 6, 2009
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    The PCV could be a problem when running, since it can potentially pressurize the crankcase and force oil out.

    I expect you just have a leaky cover. Even my brand new 1975 258 with a brand new factory valve cover leaked a little. I would also check that there is no oil pooling on top of the cylinder head after shutdown. Oil is supposed to drain back to the crankcase through holes cast into the cylinder head. I think you'd have to have a lot of gunk under the valve cover to stop the oil draining though. There's a lot of splashed oil under the valve cover, and I expect it just seeps between the gasket rather than running down into the head.

    I don't think there's any difference between the chrome cover and the factory cover, other than the plating. Clifford sells a cast aluminum cover for these engines, but it's way too expensive.

    Ok, my recipe is to use the rubber gasket like the factory supplied. Felpro sells them, and they fit good. After you remove the cover, clean the mating surface on the valve cover and on the head. Examine the valve cover closely around the bolt holes. Overtightening will bend the cover and make the metal around the holes dish in, causing (worse) leaks. Use a good straight edge and measure the flatness of the cover's gasket surface. If it's not straight, use a block of metal or hard wood as a dolly and tap the mating surface flat.

    When the cover is straight, glue the gasket into the cover (I used weatherstrip cement, but it's slightly soluble in oil, so gasket cement is probably better). Then seal the gasket to the head with a thin layer of silicone. A thin coating of oil on the head surface will make the valve cover easier to remove later, but might not be as good a seal.

    If I did one today, I'd probably try Hylomar.

    hth!
     
  3. Sep 6, 2009
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
    Joined:
    Mar 29, 2007
    Messages:
    5,916
    Have you run a straight edge on the inside edge (where the bolt holes are) to see if it is straight? Are the bolt holes dished downward due to over-tightening? If so just flatten them down and re-install. The gasket manufacture usually cautions against over-tighten of the cover

    bolts. Tim beat me to it..
     
    Last edited: Sep 6, 2009
  4. Sep 6, 2009
    73cj5

    73cj5 Member

    Maine
    Joined:
    Jan 15, 2004
    Messages:
    903
    I belive felpro discontinued the rubber gasket. So your stuck with cork. I used permatex on the cover and the head, no leaks yet.
    Posted via Mobile Device
     
  5. Sep 6, 2009
    Chilly

    Chilly Active Member

    Joined:
    Mar 12, 2007
    Messages:
    1,486
    Flatten as per previous post to get rid of the deformation. Dab a little black RTV (blue is so ghetto, red is just plain confrontational) on the cover side of the gasket and also on the cover (yes, both sides, it matters). You could smear it on like you're making a PB&J but that's just wasteful and unnecessary if your cover is flat. Let it set up overnight with the gasket side down on a flat surface. Maybe put a few pounds of weight on the top of teh cover for good measure. Letting it cure to the cover keeps it from squirming off the cover when you install it on the head Clean the crap out of the gasket surface on the head. Dab black RTV on the gasket and head (yes, both sides, and black for reasons already discussed). Now here's where I get all crazy. Put a little dab of RTV on the top of the cover around the bolt hole and also a little bit around the underside of the bolt head. Install cover, snug up just enough to keep things in place, push down firmly on the top of the cover to make sure the surfaces mate up, snug up a little more. The key is less is more. You aren't gronking on a pressure vessle lit, it's just a tin cover that needs to not shake off. Less is more, as a smelly hippie would say.

    Chilly
     
  6. Sep 6, 2009
    sterlclan

    sterlclan Member 2022 Sponsor

    exploring the...
    Joined:
    Feb 21, 2009
    Messages:
    3,869
    what you got something against smelly hippies?:)
     
  7. Sep 7, 2009
    Chilly

    Chilly Active Member

    Joined:
    Mar 12, 2007
    Messages:
    1,486
    Nothing that a bar of soap and a haircut won't cure. :)
     
  8. Sep 7, 2009
    Mugzilla

    Mugzilla Member

    Pompano Beach,...
    Joined:
    Jul 31, 2003
    Messages:
    203
    Will a factory steel valve cover solve my woes? I do not think my valve cover gasket is mating between each surface well...

    Also, anyone have a pic of where these oil drainback holes are?

    I do not have oil leaking out during operation. I don't think it is because of pooling, but because of the PCV. I have monster vacuum sucking off of the PCV. It think that is sucking the oil to keep it in (As well as a healthy dose of air into the engine...
     
  9. Sep 7, 2009
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    You understand how the PCV system works? All it does is remove any crankcase fumes and blow-by. It connects to manifold vacuum, so it will have a big vacuum when the engine is running. Pretty sure the valve just cuts off the flow when there's no vacuum. Make sure the valve moves freely - clean it in solvent and shake it - you should hear it move. Or just replace it - they are cheap.

    Generally if the PCV is not working, you tend to get oil in the air cleaner. Propelled by crankcase pressure, atomized oil travels out the crankcase inlet and condenses in the air cleaner.

    You can get a different valve cover, but I'd first examine this one to see if it's straight. I don't have much confidence in replacement parts these days - I'd worry that you are trading a chrome cheap import repop for a painted cheap import repop. A used factory cover might be better, but it too could have been distorted by overtightening in its previous life.
     
  10. Sep 9, 2009
    1974Sixer

    1974Sixer Member

    Eureka, Tx
    Joined:
    Jan 30, 2009
    Messages:
    154
    My cork gasket cured my leak, but that was after straightening bends and dings from the previous over torquing of the bolts. So far so good.
     
  11. Sep 9, 2009
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Felpro has a reputation for quality stuff, so if they discontinued the rubber gasket in favor of their cork gasket, it's probably ok.

    The old cork gaskets would shrink in the package as they'd dry out. Maybe the new ones are treated with something to keep them soft and supple (Oil of Olay for gaskets?)
     
  12. Sep 9, 2009
    1974Sixer

    1974Sixer Member

    Eureka, Tx
    Joined:
    Jan 30, 2009
    Messages:
    154
    I think you're on to something.
     
  13. Sep 10, 2009
    Mugzilla

    Mugzilla Member

    Pompano Beach,...
    Joined:
    Jul 31, 2003
    Messages:
    203

    OK, I think I have this part messed up: I have the PCV valve hooked up to manifold vacuum. If the PCV valve is supposed to maintain a small amount of crankcase pressure, is full-on vacuum too much for it? (I guess the real question is, is the PCV supposed to be hooked to manifold vacuum, or just to the bottom of the air cleaner (Tiny amount of vacuum?).
     
  14. Sep 10, 2009
    uncamonkey

    uncamonkey Member

    Greeley CO
    Joined:
    Jun 2, 2009
    Messages:
    2,104
    If the PCV is bad it can cause an issue with crankcase pressure.
    It's supposed to draw a vacumn in the system, hook to the manifold vac..
    On the other hand there should be a source of air coming into the motor. Usually it was a hose hooked into the air claener or a filtered breather of some type.
     
  15. Sep 11, 2009
    Mugzilla

    Mugzilla Member

    Pompano Beach,...
    Joined:
    Jul 31, 2003
    Messages:
    203
    So, if my valve cover only has a PCV hole and a fill hole, I am messing up, right?

    Should I replace it with a breather that vents into the air cleaner? (Those little air filter-looking breathers make a mess!)
     
  16. Sep 11, 2009
    uncamonkey

    uncamonkey Member

    Greeley CO
    Joined:
    Jun 2, 2009
    Messages:
    2,104
    Seems to me that most engines of that peroid had some sort of fresh air supply to the engine along with the PVC system. Yours may have gotten lost when the chrome cover was installed, or you may need to find an oil filler cap with the vent line that goes to the air cleaner.
    If your engine is worn enough to get significant blow-by past the pistons, your air cleaner will start to accumulate a fair amount of oilnear where the tube comes in.
    One of the joys of an older vehicle.
    I was having a similar problem on my V6, oil leaking out of the base of my dip stick tube. Stuck on a vented oil filler cap and the problem is much better, so far.
     
  17. Sep 11, 2009
    Rick

    Rick Member

    Hanson,Ma.
    Joined:
    Oct 19, 2006
    Messages:
    287
    Mine originally had the PCV valve in the rear hole in the cover and the fresh air hose connected to a fill cap on the front with a plastic elbow through the middle of the cap, that was connected to the air filter housing. The PCV valve is connected to the fitting on the intake manifold which is located beneath the carb. It's the bigger fitting in the bunch and fits the proper size hose.
     
  18. Sep 11, 2009
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    This is the gist of it. The PCV system removes crankcase fumes. To remove the fumes, the PCV valve is connected to manifold vacuum, typically at the base of the carburetor.

    To provide a flow of air, the crankcase needs an inlet. The inlet on a 232 or 258 is through the top of the valve cover, connected to a hose and a separate filter in the air cleaner. The AMC V8s admit air to the crankcase through the oil filler cap. The filler cap has a filter in it, and also connects to the air cleaner for a source of (mostly) clean air.

    The PCV system is connected to manifold vacuum, and sucks on the crankcase. The low pressure in the crankcase takes in air to the crankcase via the crankcase breather.

    I don't think I can explain it any clearer than that.
     
  19. Sep 11, 2009
    1974Sixer

    1974Sixer Member

    Eureka, Tx
    Joined:
    Jan 30, 2009
    Messages:
    154
    First time I've ever fully understood it.

    Tim, let me know if you ever decided to write children's book about CJ-6's. I want a copy!
     
  20. Sep 22, 2009
    barely3

    barely3 Spending my retirement

    Eugene, Oregon
    Joined:
    Apr 16, 2008
    Messages:
    28
    I would use a product called Gaskacinch. It is tacky, like tar but will keep the gasket in place and won't leak
     
New Posts