MLS head gasket?

Discussion in '40- & 55-Series Tech' started by amaurer, Feb 20, 2009.

  1. amaurer

    amaurer

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    Forgive me for cross posting from the diesel section, but this is a general issue.

    Due to a shoddy, and unnecessary, previous head gasket replacement, I'm experiencing the fun all over again. This time I got an OEM head gasket and was surprised to find that the new gasket is MLS (multilayer steel) (the original p/n has been superceded several times)

    I know MLS gaskets are superior in many ways, but I've heard they're very picky about flatness and low-roughness surfaces. While I have had the head resurfaced, I wasn't expecting an MLS gasket so I didn't pay any attention to the finish the shop created. I also have no real way to resurface or even measure the block's flatness (short of pulling the whole engine - but this is my DD and I've been already down for a week).

    So, am I in for trouble with this MLS gasket, or does Toyota know best?
     
  2. bsevans

    bsevans Focus on the Journey

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    I guess I need to be schooled on what a MLS gasket looks like. Could you post a photo. I know that Toyota went from head and manifold gaskets that were metal (dimpled) on the contact surface (both sides) to a non metalic contact layer on both sides. If your gasket has an exposed metal layer then you have the old style gasket.
     
  3. amaurer

    amaurer

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    i can snap a pic tonight, but this is not the old dimpled style. MLS gaskets are several layers of flat (non dimpled) steel thats been coated with black rubber (ok, its fancier than rubber, viton i think).

    the original gasket and my first aftermarket replacement were dimpled. this one is smooth, has a viton coating, and feels heavier/stiffer. it has the right pn stamped on it, and is the right dimensions, so no question there.

    do i use all the same torques and such too?
     
  4. bsevans

    bsevans Focus on the Journey

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    That's the HG I used when I had a valve job done. Same torque and then re-torque after the engine idled at temp for 15-20 minutes. I like the new design and feel it will seal better than the dimple design.
     
  5. ranger

    ranger

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    You can measure the blocks deck surface with a straight edge and feeler gauge.
     
  6. Rice

    Rice

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    You should have no trouble with the MLS. While the big advantage is their ability to seal metals with different expansion rates they also do well with like metals. Regardless, if this is your second time doing the job certainly take the time to verify a flat mating surface.
     
  7. amaurer

    amaurer

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    well, its in there now. heres a pic of the gasket for posterity
    IMG_4809-800.jpg
     
  8. grant5127

    grant5127

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    Thanks, DuPont!

    Most late model engines now use Multi-Layer Steel (MLS) head gaskets because they are much stronger and more durable than nonastestos or graphite cylinder head gaskets. Aftermarket MLS head gaskets are now available for many "problem" engines that are known to eat head gaskets............

    MLS technology was developed to overcome sealing challenges. The number of layers in an MLS gasket ranges from two to five, depending on the engine's sealing characteristics. Generally, the more layers, the more motion the gasket endures.................

    Felpro now has introduced the "New Breed" (PermaTorque) mls head gaskets that requires no re-torque installation............:clap:

    Man, I gotta say; They sure got close with the hole punch on your gasket there...

    Are the fire rings distorted enough to cause worry?
    IMG_4809-800 copy.jpg
     
  9. bsevans

    bsevans Focus on the Journey

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  10. grant5127

    grant5127

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  11. amaurer

    amaurer

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    The design of the fire rings is kinda funny, unlike on a composite gasket where the ring is a metal ring that surrounds the cylinder and then is folded back over the upper and lower surfaces of the gasket, on this one the rings are formed by the uppermost steel layer of the gasket wrapping through the holes and then bending back over the other layers.

    So what you're seeing is the side without a fire ring per se; you're seeing the side of the gasket that bends down through the holes. The difference in coloration aren't from fire rings, for some reason they saw fit to not apply the rubberized coating in those areas.

    Here are two zoomed in pictures of the top and bottom of that spot near the "fire ring". The top photo is the top of the gasket, which folds down through the cylinder holes - you can see it just looks close because of some spurious rubber. The botton photo is the other side, which shows the upper layer folded back onto the lower face.
    firerin2.JPG firering.jpg
     
  12. amaurer

    amaurer

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    A little confused on the re-torque. Do I idle until the engine is at temp (going to take an HOUR!) or do I bring it to temp with some driving and then idle for 15-20? And do I let it cool before retorque or do it hot?
     
  13. malcb

    malcb

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    Would it get up to temp faster if you restricted airflow through the rad?
     
  14. amaurer

    amaurer

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    Maybe, maybe not. Tstat will be closed while warming up so radiator shouldn't be doing much.

    EGTs while idling are only ~180F, there just isn't a whole lot of heat available.
     
  15. donny paradise

    donny paradise

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    What is the torque on those diesels? :confused:
     
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