1994 cadillac sedan deville 4.9l please help!!
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HT4100 4.1, 4.5, 4.9 Discussion, 1994 cadillac sedan deville 4.9l please help!! in Cadillac Engine Technical Discussion; Problem, please help I own a 1994 Cadillac Sedan Deville with a 4.9 motor Shortly after I purchased the vehicle ...
  1. #1
    lyonsheart5000 is offline Cadillac Owners Member
    Automobile(s): 1994 Cadillac Sedan Deville
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    1994 cadillac sedan deville 4.9l please help!!

    Problem, please help
    I own a 1994 Cadillac Sedan Deville with a 4.9 motor
    Shortly after I purchased the vehicle used I noticed a small knock/tap in the motor during minimum acceleration, but the knock/tap would vanish as the acceleration continued until I would come to a stop and start back when I would accelerate again until I picked speed up once again.
    Well, a friend of mine suggested that I use some Lucas Oil Treatment.
    I did so, and the knock/tap seemed to disapear.

    Now since it is cold outdoors when I first start my Cadillac in the morning I am am hearing a terrible knock I assume from the motor. I am far from a mechanic.

    I took this Cadillac to the Chevrolet dealer here in town and had the service manager listen to the small tap/knock before I put the Lucas Oil Treatment in it and his opinion was that the cam was making the noise and that it would only get worse with time.

    Please give me some valuable information on this problem?
    I have always wanted to own a good Cadillac, and I don't want to get rid of this car if it is not a serious problem

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  3. #2
    Sevillian273's Avatar
    Sevillian273 is offline Cadillac Owners Connoisseur
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    Re: 1994 cadillac sedan deville 4.9l please help!!

    It sounds like you have the ever so popular main bearing thump. Do a search here for '4.9 main bearing thump' I bet your motor is over 100k. The oil treatment probably made the oil extra thick, making it take longer for the oil to reach the bearing thus making it louder until it warms up. The most common 'band-aid' for the thump is to switch to Shell 15w-40 Rotella T.

  4. #3
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 1994 cadillac sedan deville 4.9l please help!!

    How cold is cold? -30 like in the northeast? How many miles on it? I think these cars have roller cams and it should be pretty rare to have cam noise. Usually if a knock gets much worse in cold weather it is piston slap. I haven't heard of any piston slap problems with the 4.9s. If the oil light works and isn't flickering then that is a good sign. It may have been abused at some time in its life and developed an unnatural problem.

  5. #4
    lyonsheart5000 is offline Cadillac Owners Member
    Automobile(s): 1994 Cadillac Sedan Deville
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    Re: 1994 cadillac sedan deville 4.9l please help!!

    Yes, the cold that I was referring to is in the lower 30's
    I am far from a mechanic which is why I looked to this forum for some advice.
    It actually kinda sounds like a lifter to me, but like I said I am not a mechanic....lol

  6. #5
    frostycadillac is offline Cadillac Owners Member
    Automobile(s): 1968 DeVille, 1985 Seville, 1990 Deville, 1994 Deville,
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    Re: 1994 cadillac sedan deville 4.9l please help!!

    Quote Originally Posted by lyonsheart5000 View Post
    Problem, please help
    I own a 1994 Cadillac Sedan Deville with a 4.9 motor
    Shortly after I purchased the vehicle used I noticed a small knock/tap in the motor during minimum acceleration, but the knock/tap would vanish as the acceleration continued until I would come to a stop and start back when I would accelerate again until I picked speed up once again.
    Well, a friend of mine suggested that I use some Lucas Oil Treatment.
    I did so, and the knock/tap seemed to disapear.

    Now since it is cold outdoors when I first start my Cadillac in the morning I am am hearing a terrible knock I assume from the motor. I am far from a mechanic.

    I took this Cadillac to the Chevrolet dealer here in town and had the service manager listen to the small tap/knock before I put the Lucas Oil Treatment in it and his opinion was that the cam was making the noise and that it would only get worse with time.

    Please give me some valuable information on this problem?
    I have always wanted to own a good Cadillac, and I don't want to get rid of this car if it is not a serious problem
    I realize this post is an older post, but relative to the problem at hand for anyone searching for this information. A few years ago, I replaced all the bearings in my 94 Devillie 4.9 with the main service bearings that GM made to correct this problem. The service bearings are obsolete.I chased down these oem bearings from obsolete GM part sources all over the country. I actually found three sets, so I purchased all three sets 1 - 5. I have one set left, these are impossible to locate. I am selling a full set if anyone is interested. Cost new $1426.00 from obsolete GM parts. sjflifecoaching@gmail or 813*417*1048(text or call). Replacing all five bearings does fix this problem, my deville had 116k miles on it when I replaced them, it now has 170k miles as is quite as a church mouse in a kiddie car !

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