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  1. #1
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    5.7 Oil Consumption and Smoke- Intake Gaskets?

    My 2006 300C with a 5.7 currently is sitting at 194k miles. A reman motor with 40k miles was put in about 10k miles ago, and completely remanufactured heads were also used. At the moment, I have a warm start blue smoke issue from the tailpipe and it will also let out a puff after idling for a few moments, or upon deceleration such as on a hill. Seems like the classic symptom of valve seals, but I have my doubts considering the age of the heads. The car runs pretty well, with no codes, but will idle rough after a bit, likely due to the plugs and intake charge being fouled with oil. Oil consumption is about 1 quart every 600 miles. Oil pressure is great, and when cruising, there is no oil smoke.

    The dealer is noting that the intake gaskets are leaking, which is visually evident by the oil residue on the heads. Could this be a cause of the oil consumption and smoke? Always considered it to potentially be a intake gasket issue.
    *Formerly "SoCalMoparKid and SoCalMoparDude"*

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  2. #2
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    Are you absolutely sure the engine and heads that were installed are "as advertised"? Burning that much oil (one quart) in that short of time (600 miles) sure indicates something is amiss. Have you checked the spark plugs for oil fouling? If the engine was assembled properly, the 5.7 intake gaskets are pretty idiot proof and shouldn't leak, unless the manifold is loose. The 6.1 intake setup is a different story though. Even if they did leak, you'd be getting a vacuum leak.....no oil should be present. A valve cover being loose could cause some oil leakage though. It's also pretty tough to screw up a valve cover gasket too. Check both for tightness using the correct torque specifications and torque them in the correct sequences. Also, pull a plug from each cylinder and have a look for oil fouling. While you have these plugs out, you may also want to do a compression test.....it'll only take about 15 minutes, if that, since they're already out. Is there any oil on the ground in the morning when you go out to start it? Is the PCV system working properly....hoses good, valve fairly new? Have you checked the back side of the throttle body butterfly and intake plenum for contamination and oil puddling?
    Last edited by magnuman; 08-16-2019 at 04:54 PM.
    06 300CSRT8, Comp cammed, 85mm TB, HP/DS Tuners, 06 Jeep GCO and 05 Magnum RT both modded almost the same, MDS "ON" Lt, Fumoto Drain Valves, BT Catch Cans, SRT8 CAIs, AFE Filters, Sonnax Trans Line Press Booster, SC, DS and HP Tuners, Transgo Shift Kit, ARH Long Tube Hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvrs, SRT8 frt/rear bumpers, FRI Sidewinder Cams advanced (Jeep 6*/Maggie 10*), 6.1 valvetrain, SLP 25% UD Pulley, BBK and Arrington 90mm T-Bodies, SOS Ign Coils,TEA ported/milled heads w/new valve seats, SRT Reps.
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  3. #3
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    Quote Originally Posted by magnuman View Post
    Are you absolutely sure the engine and heads that were installed are "as advertised"? Burning that much oil (one quart) in that short of time (600 miles) sure indicates something is amiss. Have you checked the spark plugs for oil fouling? If the engine was assembled properly, the 5.7 intake gaskets are pretty idiot proof and shouldn't leak, unless the manifold is loose. The 6.1 intake setup is a different story though. Even if they did leak, you'd be getting a vacuum leak.....no oil should be present. A valve cover being loose could cause some oil leakage though. It's also pretty tough to screw up a valve cover gasket too. Check both for tightness using the correct torque specifications and torque them in the correct sequences. Also, pull a plug from each cylinder and have a look for oil fouling. While you have these plugs out, you may also want to do a compression test.....it'll only take about 15 minutes, if that, since they're already out. Is there any oil on the ground in the morning when you go out to start it? Is the PCV system working properly....hoses good, valve fairly new? Have you checked the back side of the throttle body butterfly and intake plenum for contamination and oil puddling?
    I personally did not rebuild the engine myself. It was a low mile donor out of a wrecked LX, and the PO dropped new pistons, rings, bearings, and timing set in it. The heads are supposedly reman pieces with the valve seat issue handled. The previous mill spun a bearing, which was the reason for the current mill being put in.


    I will pull a couple of plugs. Currently, no codes, and no misfiring detected, either by ear or by the PCM.

    I put a new PCV valve in and all of the hoses appear to be good. No oil on the oil filter. I will pull the throttle body off and have a look at the floor of the manifold for any oil pooling.

    Temps during operation are normal (203-206 degrees on average) and performance is normal.

    There are a few drops of oil the next morning after running, but that is either coming from the rear main, or up high from the intake gasket.

    Water pump needs to be resealed, as it is leaks a bit from time to time when it sits.

  4. #4
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    My guess is that the PO did not do a good job rebuilding the engine. If you don't "clock" the rings correctly, it could cause oil consumption. And a quality head rebuild is not cheap. Yeah, you can buy "reman" heads off ebay for $200 each but they may not be the best.

  5. #5
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    Sounds like valve seals.
    Start with cheap first. As stated as above. Make sure everything is tight. Compression test. Then valve seals. Should be able to do in chassis.


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  6. #6
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    Quote Originally Posted by 2005rtmag View Post
    My guess is that the PO did not do a good job rebuilding the engine. If you don't "clock" the rings correctly, it could cause oil consumption. And a quality head rebuild is not cheap. Yeah, you can buy "reman" heads off ebay for $200 each but they may not be the best.
    This is a real possibility if the builder was inexperienced. After all, it looks so much nicer to have all the ring gaps lined up in a row.....NOT. Years ago by father-in-law bought a new Cadillac that burned a quart of oil about every 400 miles. The dealer ultimately tore it down and all ring gaps on all pistons were lined up as straight as could be.

    IMO, IF the valve seals were installed correctly, there's almost no way this could be a problem.

  7. #7
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    Quote Originally Posted by magnuman View Post
    This is a real possibility if the builder was inexperienced. After all, it looks so much nicer to have all the ring gaps lined up in a row.....NOT. Years ago by father-in-law bought a new Cadillac that burned a quart of oil about every 400 miles. The dealer ultimately tore it down and all ring gaps on all pistons were lined up as straight as could be.

    IMO, IF the valve seals were installed correctly, there's almost no way this could be a problem.
    Supposedly, the previous owner has rebuilt 4 or 5 pre-Eagle 5.7s and used the same local provided for the cylinder heads (specialize in 5.7/6.1s). He stated that he went through and replaced the cylinder heads on his wife's 300C as well.

    To me, it seems pretty difficult to install the valve seals incorrectly. More likely that one or two broke away. My concern is if the PO just re-ringed the pistons and shoved them in,without cleaning up the cylinders much.

    Checked compression on a few cylinders last night. All were great and within a few percent of each other. Will do the others tonight.

    Runs great and clean at throttle, but as soon as you let it idle for a bit, then give it a rev or take off hard from a light, there comes the blue cloud, only to go away at cruise again. Fuel mileage is unaffected and oil shows no signs of contamination.

  8. #8
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    In the meantime, I am going to continue driving the car while I diagnose to keep miles off of the others and just keep up on the oil level. The plugs did have some oil soot, but I cleaned it off.

  9. #9
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    5.7 Oil Consumption and Smoke- Intake Gaskets?

    All the plugs looked the same?


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  10. #10
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    Quote Originally Posted by DBL.DWN View Post
    All the plugs looked the same?


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    More or less, yes. One or two were a little worse off, but not largely. None of them were a normal light tan like they should be.

  11. #11
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    Check the engine vent to make sure it isn't building up pressure in the base. I suppose these cars have an orifice instead of a PCV.

  12. #12
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    Quote Originally Posted by MoparJP View Post
    More or less, yes. One or two were a little worse off, but not largely. None of them were a normal light tan like they should be.
    Then you can probably rule out valve seals. I would think it would be rare for them all to leak the same.
    Have you looked at the pcv valve?

  13. #13
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    Quote Originally Posted by DBL.DWN View Post
    Then you can probably rule out valve seals. I would think it would be rare for them all to leak the same.
    Have you looked at the pcv valve?
    PCV was replaced a few weeks ago with an over the counter parts store brand. No noticeable changes. Wondering now if I need to have a closer look at the whole assembly itself to see if something is amiss.

    Drove 40 miles to work today. Ran flawlessly, except for the obvious smoke as noted on warm start ups and when jumping on the gas after idling, or after high vacuum conditions. It does start to idle ever so slightly rough after a few moments of idling, but not a clear misfire or anything notable watching the RPMS thru EVIC. Likely a bit of oil getting to the plugs, or possibly a vacuum leak.

  14. #14
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    Just curious I suppose. If the donor engine was low miles, why would the guy rebuild it? Seems curious to me? A little fishy?

  15. #15
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    Quote Originally Posted by 2005rtmag View Post
    Just curious I suppose. If the donor engine was low miles, why would the guy rebuild it? Seems curious to me? A little fishy?
    Low miles is a relative term the PO kept using that I should probably refrain from using as well. The donor unit had 65k miles on it.

    Believe me, it was to me as well. The reasoning was that since they were replacing the original unit that spun a bearing, they didn't want to overlook anything with the replacement, so they rebuilt the bottom end. He did show me the manifest and receipts of the parts utilized.

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