4 Bad Headgaskets
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Northstar Engines and System Technical Discussion Discussion, 4 Bad Headgaskets in Cadillac Engine Technical Discussion; So I recently acquired not only 1 but 2 vehicles with bad headgaskets. A 2005 Bonneville GXP and a 2005 ...
  1. #1
    Northstar125 is offline Cadillac Owners Fanatic
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    4 Bad Headgaskets

    So I recently acquired not only 1 but 2 vehicles with bad headgaskets. A 2005 Bonneville GXP and a 2005 Cadillac Deville. Having never done one before I hope I'm not getting in over my head but I have read the extensive threads from different members detailing their headgasket replacement. The Bonneville has no oil leaks while the Deville does so I'm hoping not to have to tear into the bottom end of either one but we'll see when we get to that point.

    The Bonneville runs very rough and erratic with P0300 random multiple cylinder misfire. Whereas the Deville only has a misfire number 2 and seems to run fine when you "get on it." And the owner said the overheating was very intermittent and only occurred 3 times within 500 miles of driving.



    Anyways I'm looking for a list of things that I will need before I begin my quadruple bypass between these 2 cars. I'm assuming the engines are the same? So one service manual should be sufficient to do both.


    Here's a list of the things I have already purchased or will be purchasing as I get ready to do the job. Let me know if there is anything I am missing or anything I have listed that I WILL NOT need.

    I really don't want to go overboard here as both of these are budget builds BUT something as cheap as $8 radiator hoses WILL most definitely get replaced.

    Purchased:
    Kent Moore J42841 Rear oil seal remover
    Metal fuel line disconnect tool
    Front motor mount (not sure if it will be needed or not)
    KM J45930-A Rear oil seal press (Looking on ebay is $165-$200 fair or can I find one cheaper somewhere?)



    Studs
    Head gaskets
    Intake gasket
    Valve Cover gaskets
    Oil pan gasket
    Waterpump
    Thermostat & Seal
    Spark Plugs

    Oil
    Coolant

    TCC Solenoid?
    Transmission Side Cover Seal
    Transmission Fluid

    Radiator Hoses
    Exhaust Manifold Gasket
    Front Seal and timing cover gasket
    Rear main seal

    I usually buy ALL Felpro gaskets? Is that fine or are the OEM GM recommended in any instances?


    Also what is the best way of checking the block and head flatness? Is it absolutely necessary to take the heads in and have them gone through? Or is there a way I can check them myself?

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 4 Bad Headgaskets

    Just lay a straight edge on the head and see if you see light under it, but I doubt you will. The heads never need any work.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 4 Bad Headgaskets

    Block deck checks, machinist's straightedge - laid diagonally from corner to corner - both ways - X. Front to rear, centerline of the cylinder bores. Essentially the same for the heads.

    ......... and you do not mill the block if the deck flatness exceeds .004" - you replace it. The heads will take a .008" mill from stock - total.

    The 2005 Northstar (from 2000 - - on) has roller cam followers with stationary lash adjusters. (Picture courtesy of JimD)
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    04GrandAmGT's Avatar
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    Re: 4 Bad Headgaskets

    Quote Originally Posted by Northstar125 View Post
    I usually buy ALL Felpro gaskets? Is that fine or are the OEM GM recommended in any instances?
    Felpro works just fine, just NEVER use there rear main seal. i hope the rear main you purchased was a GM Factory replacement.


    Need parts for your Northstar Engine? www.northstarperformance.com

    Evrett, Sales Executive of the SureGrip™ Cylinder Head Stud Kit

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    Fifty9cadillac is offline Cadillac Owners Member
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    Re: 4 Bad Headgaskets

    Make sure everything is factory replacement. I get all of my oem stuff from GM parts. But check the site and vendors for other places too. I can't say i've use the SureGrip stud kit. . . yet. Good Luck.

  7. #6
    JoeTahoe is offline Cadillac Owners Fanatic
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    Quote Originally Posted by 04GrandAmGT View Post

    Felpro works just fine, just NEVER use there rear main seal. i hope the rear main you purchased was a GM Factory replacement.
    I agree with this felpro top end kit and a felpro timing cover gasket. Only use the gm rear main seal. Rock auto has good prices on felpro
    04GrandAmGT likes this.

  8. #7
    Northstar125 is offline Cadillac Owners Fanatic
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    Re: 4 Bad Headgaskets

    Ok. Thanks for the advice.

    I've got another question for you guys. Had to move the GXP the other day and it started making some weird noise (didn't sound like a spun bearing but was metallic noise). Turned motor off, would not restart. So I'm assuming its hydrolocked. At this point I'm wondering if a junkyard engine wouldn't be a better course of action after all that?

  9. #8
    Submariner409's Avatar
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    Re: 4 Bad Headgaskets

    Hard to say, but metallic clanging and banging followed by a no-crank condition is usually notice of expensive noises. If the engine is hydrolocked you could not turn it over with a giant crowbar.

  10. #9
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    Re: 4 Bad Headgaskets

    An engine from a wrecking yard could be a viable solution. If it were mine I would still re-do the head gaskets and threads before installing a used Northstar since a good chunk of the work is in the engine removal/install itself. Nothing like a known set of values under the hood.

  11. #10
    rodnok01's Avatar
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    Re: 4 Bad Headgaskets

    I agree since it would be out almost silly not to do it then, if any oil leaks perfect time to fix those too.

  12. #11
    Northstar125 is offline Cadillac Owners Fanatic
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    Re: 4 Bad Headgaskets

    But if I separate the midcase then at minimum I would have to replace the metal mid-case seal and crank bearings, correct? I want to fix it right but don't want to do things that are unnecessary and spend extra money. I guess going this route I could see if the bottom end was in good shape before putting it all back together.

  13. #12
    rodnok01's Avatar
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    Re: 4 Bad Headgaskets

    Crank bearings and bolts can be reused. The rod bolts have to be replaced if removed.

  14. #13
    Northstar125 is offline Cadillac Owners Fanatic
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    Re: 4 Bad Headgaskets

    So its just the mid-case seal then? For some reason I remember reading about the bearing getting crushed/pressured or something when tightening the bolts? Was that regarding the rod bearings?

    When pulling the mid-case apart if the mains look good there is no sense in pulling rod caps, correct?

  15. #14
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    Re: 4 Bad Headgaskets

    Quote Originally Posted by Northstar125 View Post
    So its just the mid-case seal then? For some reason I remember reading about the bearing getting crushed/pressured or something when tightening the bolts? Was that regarding the rod bearings?
    Correct. That is why (to the best of my knowledge) they are not supposed to be reused.

    When pulling the mid-case apart if the mains look good there is no sense in pulling rod caps, correct?
    Actually, there is not much sense in opening the halfcase unless you are resealing it. The lower end is damned near bullet proof and the bearings seem to outlast the car.

  16. #15
    rodnok01's Avatar
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    Re: 4 Bad Headgaskets

    The only reason I pulled my half case was major oil leak that became obvious with engine out.
    Main bearings were virtually perfect after 100k.

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