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cadillac 390, loss of power and vibration

Discussion in 'The Hokey Ass Message Board' started by boomosby, Jul 7, 2012.

  1. boomosby
    Joined: Dec 20, 2009
    Posts: 413


    so i was cruising in my 60 flattop when a small vibration began. i didnt pay much attention just figured it was do to sitting for a year. i took it donw the highway and the car would not speed up , at all. i got off teh freeway and noticed teh small vibration had turned into earthquake size shaking and rattling. the car will not speed up and wheni give it gas it hiss, rattles , goes a bit, then slows back down.
    i am pretty savy with cars, so i know most often when something is up. but this time, there is no smoke, there are no knocks, no pings, no leaks, just no power, almost as if it is getting no compresiion.
    has anyone had this happen before? what is the best course of action? what does it sound like to you guys?
  2. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    Sounds like the whole bottom end went away! Old softened bearings will do that after sitting for years.
  3. ryno
    Joined: Oct 6, 2005
    Posts: 3,471


    maybe a hydro lock
    bent a rod?
    good luck
  4. Zerk
    Joined: May 26, 2005
    Posts: 1,418


    Check the harmonic balancer at the front of the crank. May have loosened or torn apart.

  5. start with the basics, check the fuel condition, because its been sitting for a while, and check the fuel pressure to see if its getting enough fuel. then check all the spark plugs to see the gap and if any signs of carbon or coolant gettin in the cylinders.
  6. 48 Chubby
    Joined: Apr 29, 2008
    Posts: 1,014

    48 Chubby
    Member Emeritus

    If the engine runs good but the car don't run good, you got a drive line problem. Torque converter bolts, U-joints, transmission, etc. If the engine won't make power but runs well with no load the distributor may have slipped. Some times the shaft will try to bind and rotate the housing.
    If you can't find the problem quickly go back to the basics and check every thing in a logical and systematic sequence.
  7. boomosby
    Joined: Dec 20, 2009
    Posts: 413


    thanks for updates guys, the tranny i have to shift manually because teh valve body sticks going from 1st to 2nd, and vice versa. i have noticed lately that when i am down shifting , i here a loud "bell" sound, which could only be the torque converter.

    also i had teh car on a lift recently and a guy asked me if i ever got vibration from the driveshaft. i told him no, but i think he jinxed me! haha.....

    i have checked for fuel, consistent, pump loosk a little slow, but that should affect driving at 15 mph...timing seemed fine, idles well, but under load wants to pick a mean fight with me....bakc to teh drawning board
  8. is the vacuum advance line installed? lol just a thought.. is it an electric fuel pump? check if the fuel pressure stays consistent under load, may not be getting sufficient fuel when driving but okay at idle
  9. BRENT
    Joined: Jun 22, 2005
    Posts: 252


  10. Riviscara
    Joined: Jul 5, 2011
    Posts: 3


    Do you still have points? I have had similar situations where the car ran OK then did not like you mention from the points sticking or closing. Also, sitting for a year could cause the bad gas we get today to varnish and get sticky. have seen this cause the valves to stick and bend pushrods which would make some cylinders inoperative. Valve covers are easy to pull on that motor, Check the basics as mentioned here first. Let us know your findings.
  11. boomosby
    Joined: Dec 20, 2009
    Posts: 413


    points were napa replaced lastyear, but will start there and see. the tranny is a terd and ha sbeen making funny noises for some time., but will do the "tune-up" thing first and see what happens after that ;p
  12. boomosby
    Joined: Dec 20, 2009
    Posts: 413


    funny story guys, i just came home after nto driving the car for two weeks, and it just decided to start working just as normal as possible , no idea what was causin the vibration or power loss , but its fine now! weeeeirrrddd
  13. interstatemaster
    Joined: Aug 7, 2009
    Posts: 101


    from the hiss, no power goes and slows down sound like a restricted exhaust. put a vacuum gauge on it and speed it up. Vacuum should increase with rpm. 17.5 to 19-20 at 3500 rpm. If it falls off maybe someone crawled up the exhaust pipe or a double wall pipe collapsed the inner pipe or a baffle came loose and is moving around inside a reverse flow muffler. All conditions I've had to diagnose on customer vehicles.
    Doing a compression test is always an advisable first step too.
  14. GARY T.
    Joined: Mar 23, 2008
    Posts: 1,985

    GARY T.
    from S.W. Pa

    Maybe it just wanted a rest LOL:D

    Years ago we had a 65 Chrysler that my wife and I still refer to as "the car that would fix itself"---Shoulda named it Christine Ha Ha. anytime it would act up---seemed like before I could look at it the problem would go away.
    Now if they all did that what would we do with all the time we would have on our hands?
  15. Really sounds like something built a nest in the muffler. The vacuum gauge should tell you what's up. If you drop the exhaust at the manifold (a lot of work I know.. ) and it perks up, you found it.

  16. Terrible Tom
    Joined: Feb 15, 2010
    Posts: 577

    Terrible Tom

    Maybe it took a drink of "bad gas", water in it or something. I've had it happen.
  17. Wowcars
    Joined: May 10, 2001
    Posts: 1,023


    With the bad vibration, I would be suspect of the harmonic balancer or torque converter. If the balancer is cracked, broken, off balance, etc it will throw off the balance of the rotating assembly and, due to harmonics, it will escalate until it comes to a stop. (You turn the car off) Now it has a chance to level out. Bad thing is, it is sometimes hard to tell if a balancer is bad, and on a 390, it may not be the easiest thing to find to 'just try'.
  18. I think I got your answer,
    Check your water-pump. Mine is doing the same thing. Try revving it up, and you can see the fan shaking, or you might be able to move it by hand. It doesn't leak coolant, but left unchecked it will fly off and go through the radiator. Time to rebuild it.

    Now you have two options since you cant buy these any longer. buy a rebuild kit for about $100 (like I did.) or buy one rebuilt for about $200 with your exchange. I recommend coughing up the two bills, because the instructions aren't very easy to understand as far as the specs go, and you are supposed to grind off part of the old impeller. (Mine is still sitting needing the rebuild).
    Let me know if you need the ordering info. I don't have it now, i'd have to dig it out, but I think I might have ordered it off of ebay. Good luck.
    p.s. There are two different kinds. a/c water pumps and non a/c water pumps. Another good reason to send it to them.

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