HT4100 upkeep and maintenence
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HT4100 4.1, 4.5, 4.9 Discussion, HT4100 upkeep and maintenence in Cadillac Engine Technical Discussion; Not sure if this is posted somewhere else or something but I just purchased an '84 coupe deVille with the ...
  1. #1
    Bobby Eyes is offline Cadillac Owners Member
    Automobile(s): 1984 Coupe deVille
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    HT4100 upkeep and maintenence

    Not sure if this is posted somewhere else or something but
    I just purchased an '84 coupe deVille with the 4100 engine, and i'd like to know
    any tips/tricks to keep it running smoothly and everything, is there anything I should keep a close eye on as I use the car?
    The oil is good, all the fluids, is there anything I should check?
    It just now turned over to 100k miles and the car definitely wasn't ever abused
    But I'd like to know any special tips or tricks, for example a particular oil or something because I read that if you use diesel oil, that can actually benefit this motor.

    So I'd just like to know how to keep this beauty stable if anybody could help I'd appreciate it.
    Thanks in advance

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  3. #2
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
    Automobile(s): 1985 Sedan DeVille
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    Re: HT4100 upkeep and maintenence

    You have a flat-tappet cam so you need an oil that's high in ZDDP to keep it from wearing flat. I've settled on Rotella 10w30 (diesel truck oil) which can be found at Walmart. The engine seems to like it.

    These engines are aluminum block, cast head, and aluminum intake manifold, and since they react to temperature changes differently they can tear up gaskets pretty quick. This was a bigger problem on the RWD models. Change fluids regularly and try not to subject the engine to radical temperature changes. I used to have an oil consumption problem that was eventually fixed with intake gasket replacement.

  4. #3
    tallpat's Avatar
    tallpat is offline Cadillac Owners Fanatic
    Automobile(s): 1986 Coupe Deville
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    Re: HT4100 upkeep and maintenence

    Congrats on the car. Never get this engine hot! never overheat! be sure to use the coolant additive gm recommends to prevent coolant leaks. change coolant every year. HT4100 4.1L has a bad reputation. The newer versions on the C Body FWD platform are better improvements were made to the engine. It is a sound design just lackluster HP 135. my 86 has 174,580 miles. and still going. well maintained engine will last for 20+ years.

  5. #4
    Bobby Eyes is offline Cadillac Owners Member
    Automobile(s): 1984 Coupe deVille
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    Re: HT4100 upkeep and maintenence

    Thanks for the replies & help guys
    Do you have a specific coolant additive name for me? I looked on google and I see some on here but I'm not sure which one would be best suited for the Cadi

    So would walmart have this coolant additive too?

    And another thing, the idle on the car is a little jittery when the A/C is on, and also, when stopped at red lights and things like that, the car jumps forward a little bit even when my foot is on the brake, any ideas on what the problem is and how I can fix that?

    And I have another question un-related to the engine: I need the rear and front fillers, could anyone direct me to either a store I could go to or maybe somewhere where I could order em online?

    Thanks alot

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: HT4100 upkeep and maintenence

    You want Barsleaks tabs (HDC) or the powdered version (G12BP). Same stuff that a GM dealer sells. Walmart should have it.

    http://www.barsproducts.com/barsleaks_products.htm

  7. #6
    tallpat's Avatar
    tallpat is offline Cadillac Owners Fanatic
    Automobile(s): 1986 Coupe Deville
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    Re: HT4100 upkeep and maintenence


  8. #7
    Bobby Eyes is offline Cadillac Owners Member
    Automobile(s): 1984 Coupe deVille
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    Re: HT4100 upkeep and maintenence

    I think that's way too expensive for just the rear fillers
    I need those, the front fender fillers, and the trunk filler

  9. #8
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
    Automobile(s): 1985 Sedan DeVille
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    Re: HT4100 upkeep and maintenence

    If you have a part number, check on http://www.vpartsinc.com/ They buy old stock from GM/Chrysler/etc

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