HT4100 Intake Gasket Question
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HT4100 4.1, 4.5, 4.9 Discussion, HT4100 Intake Gasket Question in Cadillac Engine Technical Discussion; Hello all! New to the forum. I just picked up an 85 Eldorado with 41k miles on the original engine. ...
  1. #1
    JamesG602 is offline Cadillac Owners Member
    Automobile(s): 85 Eldorado
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    HT4100 Intake Gasket Question

    Hello all! New to the forum. I just picked up an 85 Eldorado with 41k miles on the original engine. While going over the car I noticed the coolant tank was very very low. Long story short it's at my mechanics right now. After changing out a few hoses and going over the car, he concluded that the intake manifold gasket is bad. The oil looked clean, no milky residue. Not surprising on this car from what I've read. The motor doesn't have the new style intake gasket/bolts washer that GM put out as an update. Are these newer intake gasket kits still available? Anyone have a part number? He said he can get a VICTOR intake gasket, would that be better then the OEM one? Thanks! I also got the coolant sealing tabs on the way!

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  3. #2
    cadillac_al is offline Cadillac Owners Connoisseur
    Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
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    Re: HT4100 Intake Gasket Question

    I don't think these cars are known for bad intake gaskets like a Buick. Maybe he was just fishing and hoping for a bite. I would just fill the coolant and see how fast it is disappearing if at all. Since you just picked it up you don't know if it was ever full. Even better would be to change the coolant with new stuff and only use half of the sealant tabs if there is evidence of sealant tabs in there already. A lot of people hate the sealant tabs around here but i believe the problems come from people using too much of it. When you drain the coolant there is still a lot of sealant tab residue coating the entire cooling system so you almost don't need to add any more. That's why I say maybe half; it all depends what it looks like. If everything is already brown and slimy in there you can probably skip the tabs.

  4. #3
    JamesG602 is offline Cadillac Owners Member
    Automobile(s): 85 Eldorado
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    Re: HT4100 Intake Gasket Question

    Thanks for the reply. He's a good friend of mine so I'm not worried about him taking me for a ride. He filled the coolant and pressure tested the system overnight and it did not hold. He said it was the intake manifold. Should I also go ahead and replace the head gaskets while he already is replacing the intake? What year did cadillac start using the one piece cylinder head dowels? My eldroad is an early 85 model.

  5. #4
    JamesG602 is offline Cadillac Owners Member
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    Re: HT4100 Intake Gasket Question

    My motor has black valve covers with a few fins

  6. #5
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: HT4100 Intake Gasket Question

    I beg to differ! This engine was extremely prone to intake gasket failure. Usually the first sign was milky resiue under the oil filler cap. They corrode at the front where the coolant transfers from one head to the other. Any name brand aftermarket intake gasket will seal it and hold during your lifetime. I am not a believer in sealant tabs. They were invented to seal any porosity issues with the new aluminum blocks and will not prevent gasket failure. Change head gaskets? why? not needed in your situation. Best practice is to change, not flush the coolant every 24 months regardless of miles driven. Old coolant looses its corrosion protection and because the heads are cast iron and the blocks aluminum, corrosion happens first at the intake sealing surfaces. I was there when this engine was introduced and was a service Mgr for Cadillac thru the early 90's.
    Mr.BayArea likes this.

  7. #6
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
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    Re: HT4100 Intake Gasket Question

    Dont forget about the resulting excessive cam wear that acompanies intake gasket coolant seapage!

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