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Manifold Bolts Broken

Discussion in 'Chevy Trucks' started by te snow, Aug 4, 2009.

  1. te snow

    te snow Member
    Messages: 46

    I have a 2004 GMC Sierra 2500HD with 2 manifold bolts that have rusted away at the top front. The passenger side manifold is what I am having trouble with. I am expecting more to break when trying to remove the manifold in order to repair threads.Does anyone know if it is possible to drill out the old bolts through the wheel well and inserting a heli coil? It does look possible to me, then again should I take the chance of having to buy a new head.

    Thanks in advance for your help,
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Yes you can access the bolt holes for thread repair if necessary BUT, don't simply go drilling into the head to retrieve the broken bolts first. Most times you can get the remainder of the bolt(s) out by welding a nut to them and just threading them out.

    Nice thing is you're working with an 8.1 which of course has the good old fashion iron heads. Much more forgiving. :nod:
  3. te snow

    te snow Member
    Messages: 46

    Thanks B&B. I actually have one that the welding trick will work on and the other broke off even with the head.
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Build it up with weld first or start with a flat washer and then weld the nut on. Works 95% of the time on fasteners that are broken off flush.

    The 5% that it doesn't is then reserved for the drill bit. :eek:
  5. aeronutt

    aeronutt Senior Member
    Messages: 262

    If you do end up needing to drill, use a Dremel tool to flatten the bolt first so you can center punch EXACTLY in the middle of the bolt. I've done this with a drill bit that's just big enough to remove the core, but not the threads. This leaves a nice little coil of threads that pulls out with needle-nose pliers and then you can clean up the old threads with a tap. No heli-coils required! Whatever you do, don't break off an easy-out inside the bolt or you'll never be able to drill it again.

    A less desireable method that I've actually had work (sanity is not my strong point...) is to drill a 1/8 inch hole directly down through the threads. Yes, that means you take out half the threads from the block and half the threads from the bolt. This gives easy access to spray penetrating fluid all the way down and gives a better chance of working for the welded-on washer/nut trick that B&B detailed. Once the old bolt is out, a new one screws in and holds just fine with a small portion of one side missing some thread.

    Post up some pics and let us know what you end up doing.
  6. IMAGE

    IMAGE Sponsor
    Messages: 1,747

    I have to ask, what kind of mileage do you get with the 8.1? it cant be worse then the 6.0 gassers...
  7. 70monte

    70monte Senior Member
    Messages: 468

    Why are broken manifold bolts a problem on this generation of engines? I don't seem to remember the last generation of V-8's having this problem.

  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Mostly because of the alloys used in the bolts construction and the components that are in close proximity to one another, namely a stainless steel manifold held against an iron head with a soft bolt. The bolts are designed to stretch and give as needed to allow the manifold to expand and shrink with the temperature changes they endure, but it seems the bolts were manufactured too soft to hold up to years of use in the environment they were "designed" for. Hence broken bolts.
  9. 70monte

    70monte Senior Member
    Messages: 468

    Thanks for that info. I have been curious about this problem.

  10. Gear_Head

    Gear_Head Senior Member
    from IL
    Messages: 245

    my old 79 Ford was rusted so bad at the exhaust manifolds, we ground the heads off flat and removed the manifolds. Lots of PB blaster, a little heat, and a Snap On stud remover removed them with ease. Just a thought
  11. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Someone goes to do the job next time you might consider this. If you have a cutting torch heat the bolts red hot about 3 times. Then try removing the studs / bolts. This burns off the oxidation that welds the studs / bolts to the head. Drive a metric impact socket on the rust glob. Pull if off before you get it all the way out. I have even zipped off (with an air cut off ) the heads of the bolts / studs and removed the exhaust manifolds then dealt with the fasteners. Use a small pipe wrench or grind flats on the shaft with the air cut off to use a small wrench or such. I try my dang'est to not break off fastener's in a head, it just makes way too much work to fix it.
  12. te snow

    te snow Member
    Messages: 46

    Thank you all for your input on this repair. I took off the manifold yesterday and had 3 out of the 8 bolts break, 2 of which are not flush with the head. Taking the splash shield off the right front wheel well deffinetly helped alot to see what I was doing and will help by far when extracting the bolts.

    As for IMAGE's question, I get about 7 MPG with a trailer and average 10 MPG in city and highway driving.