M11 exhaust manifold bolts

Discussion in 'Trucks [ Eighteen Wheelers ]' started by metric adjustable, Nov 12, 2011.

  1. metric adjustable

    metric adjustable Light Load Member

    140
    75
    Dec 16, 2010
    dunno; gps is down
    0
    I own a '99 Freightliner with an M11 cummins under the hood. So far the engine as been good to me, but has a couple of annoying problems. The worst one (to me) is the #6 cylinder lower exhaust manifold bolt. The ###### thing cannnot seem to last longer than a year, and keeps snapping off flush with the cylinder head. Lots of time to drill out, since it is partially under the cab.

    In the years i've owned the truck, it has gone through six #6 lower manifold bolts, and one upper on same cylinder. Nothing is contacting the cab, the cylinder head is not original, the exhaust manifold is the only original thing in that area.

    Any ideas why this particular bolt keeps snapping off? Is it just perverse chance that the only one breaking regularly is the hardest one to get at?
    Am I the only one with this minor yet annoying problem?
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. Sportster2000

    Sportster2000 Road Train Member

    1,480
    885
    Jan 5, 2008
    Indiana
    0
    I would take a look to see if the exhaust manifold or head is a true flat surface. Other than that I don't know.
     
    metric adjustable Thanks this.
  4. bender

    bender Road Train Member

    2,105
    1,347
    Jul 20, 2010
    Don't Kid Yourself
    0
    I agree, exhaust manifolds will distort when engine has been operated with broken or missing mounting bolts/studs. Also, the manifold must be allowed some movement on the mounting when expanding and contracting during temp change. Over torquing the mounting bolts can hinder movement and pop the bolts. The mounting bolts can also be sheared off by too little clearance to the hole edge on the mounting flange. Drilling the mounting flange holes oversize in the manifold flange will allow proper movement without shearing the bolts/studs.
     
    metric adjustable Thanks this.
  5. AUSSIE DAVE

    AUSSIE DAVE Road Train Member

    1,032
    173
    Feb 21, 2010
    OZ - Brisbane
    0
    My guess also would be over torque of the bolt . On my m11 the manifold will expand and move about 1/8inch.
     
    metric adjustable Thanks this.
  6. Heavyd

    Heavyd Road Train Member

    7,625
    6,023
    Feb 4, 2009
    0
    If you have to drill out broken bolts, they weren't installed properly. Any pro will apply anti-seize to exhaust manifold bolts. That won't prevent them from breaking, but you'll never have to drill them out. They break because they are getting sheered from the exhaust manifold expanding. The manifold is suppose to have some flex at the joints between sections. If those joints do not absorb the expansion then the bolts take the stress. You may need to replace the exhaust manifold too.
     
    metric adjustable Thanks this.
  7. JohnP3

    JohnP3 Road Train Member

    1,594
    682
    Feb 21, 2010
    Rock Creek B.C. Canada
    0
    I take it you have a 112 and many times the drain for the cold air box. Air intake flactuator valve, will drain onto the exhaust manifold.
    When you remove the bolt, you want to tap out the threads then, I have a mixture of never size, ATF, and synthetic gear oil put a bit in the bolt hole then coat the threads.
    Manifold can be resurfaced on a belt sander, Both the head side surface, and the turbo mount surface, the expansion joints can not be, I have seen many people try none succeed.
     
    metric adjustable Thanks this.
  8. metric adjustable

    metric adjustable Light Load Member

    140
    75
    Dec 16, 2010
    dunno; gps is down
    0
    thanks to all... never considered drilling the offending bolt hole(s) oversize, might be worth a try before going for a new manifold. That or Grade 200 bolts, if i can find 'em.
     
  9. AUSSIE DAVE

    AUSSIE DAVE Road Train Member

    1,032
    173
    Feb 21, 2010
    OZ - Brisbane
    0
    I would NOT change the grade of the bolts, just reface manifold install new gaskets, use anti seize on bolts, and torque to spec.
     
    metric adjustable Thanks this.
  10. SmokinCAT

    SmokinCAT Road Train Member

    1,773
    1,484
    Oct 20, 2010
    Hillsboro, OH./ Adrian, MI
    0
    Also, if it is a 3 piece manifold, when you have it off hammer the ends towards the center, hopefully the back section will move enough that it will keep pressure off of the bolts when it expands.
     
    metric adjustable Thanks this.
  11. metric adjustable

    metric adjustable Light Load Member

    140
    75
    Dec 16, 2010
    dunno; gps is down
    0
    It is a three piece manifold; always thought the mating areas would allow expansion/contraction to avoid snapping bolts or warping manifold.

    If i do decide to try pulling off my own manifold, is there anything i should do beforehand to make it less likely to snap off remaining bolts? Would it be better to remove remaining bolts when engine is warm or cold?
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.