engine worth repairing? 1990 seville
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Cadillac Seville / Cadillac Eldorado Forum Discussion, engine worth repairing? 1990 seville in Past Cadillac Vehicle Discussion; My 1990 seville has a horrible knocking noise in the engine which still runs. i'm afraid to drive it to ...
  1. #1
    vacajon is offline Cadillac Owners Member
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    Question engine worth repairing? 1990 seville

    My 1990 seville has a horrible knocking noise in the engine which still runs. i'm afraid to drive it to a shop tho, fearing it will freeze up on the way.
    It is in pristine condition otherwise. Only 113k miles.
    Anyone with an opinion on whether to have major engine work done or engine replaced?

    thanks so much for any input.

    John A

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    Dead Sled's Avatar
    Dead Sled is offline Cadillac Owners Connoisseur
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    What motor is in it?

    with out hearing it for my self I can't really give you any ideas of what it would be.

  4. #3
    kcnewell is offline Cadillac Owners Connoisseur
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    It's either a 4.5 or a 4.9 and I would say it very much depends on the condition of the car. The engines mentioned are essentially the same 4.9 is basically a stroked 4.5 and they are VERY reliable engines indeed. If you are planning on keeping the car and don't mind throwing some cash at it then by all means rebuild or repair or replace the engine as far as value a GOOD used '90/'91 Seville out here goes for 4 to 5 K depending on condition. What's it gonna cost? Is it worth it to you? are the questions you need to answer. Their are some exchange engine rebuilders out there that are good....Do your homework! Ask people you think won't feed you a line of half truths and nonsense! Good luck with it!

  5. #4
    elwesso's Avatar
    elwesso is offline Cadillac Owners Master
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    Yes, do your research. If it will cost 2000 to replace the engine, go for it. You may even be able to find a used engine that would be cheaper, but i would go for the swap or rebuild. You may just go ahead and have it towed to the shop, and they will be able to figure out what is wrong. Im sure that as soon as they hear the knock their gonna want to do serious work. Fortunately, the 4.5 or 4.9 is completely rebuildable, unlike the northstar :-( . You may try putting in some higher octane fuel until you can get it fixed.

    The only things that i can think of that might be wrong is: 1. using too low an octane fuel, or 2. The knock sensors could be bad, and therefore not retarding the spark enough to compensate for the knock. I can not guarntee the accuracy of these diagnosies, but that is what comes to mind.

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    Dead Sled's Avatar
    Dead Sled is offline Cadillac Owners Connoisseur
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    got oil pressure?

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    kcnewell is offline Cadillac Owners Connoisseur
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    If we're talking about a severe mechanical knock here I.E./ Rod/ Main or wrist pen to name a few. Do not drive this car! At this point your engine is rebuildable/exchangeable more than likely. If you drive it till you have a catastrophic failure and wind up with a hole in the block you will have a MUCH bigger repair bill! Have it towed to a shop and find out what the problem is before you drive it again!

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    Dead Sled's Avatar
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    If it is only denotation (ie spark knock, ping) it could be driven very carefully and a very short distance to a repair shop. other wise you could burn a hole through the piston. But from the way you describe it, it sounds more like a rod bearing or wrist pin. To me if it is as bad as you describe it sounds like you have lost oil pressure some how and spun a bearing

  9. #8
    vacajon is offline Cadillac Owners Member
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    got an estimate for an exchange engine install. 4500 to4800.
    i can buy a good used seville for that amount.
    so i'm gonna just sell the car in broken condition.
    i have no idea what to ask for it....probably just "best offer"

    the body/paint is in pristine condition.

  10. #9
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    Katshot is offline Cadillac Owners Master
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    One thing you should check prior to throwing in the towel;
    The Caddy engines are VERY suceptable to "carbon-knock". There's no guarantee that it's carbon and NOT a bad rod, or main bearing but, it's certainly worth a little time and a few dollars to find out. Two products I have used to remove the carbon build-up are 1) Hydra-Valve-Kleen, actually an oil additive sold at auto parts and marketed for quieting noisey lifters, and 2) GM Top-Engine Cleaner, which is specifically marketed for carbon removal.
    In either case, you want to position the car away from the house (because after this procedure it's going to smoke like hell) , warm the engine if possible and then pour 1/2-3/4 of the can into the intake with the engine running. Some engines are harder than others to figure a way to get the fluid into the engine but you need to get it in fast enough to stall the engine, but not fast enough to hydra-lock it. If the engine doesn't stall by this point, shut it down and then let it sit. (CAREFUL: DO NOT POUR ANYTHING INTO ENGINE AFTER SHUT-DOWN) About 10-15min. later, fire it up and pour the rest of the can through the engine to help 'flush' out deposits. If you're lucky, at this point the knock will be gone. The engine WILL be smoking quite a bit but that will taper off and stop after a little while. Then I take it out and give it a good "blowing-out" by doing a couple full-throttle runs.
    I know this may sound strange but, a carbon knock can easily be mistaken for a bearing knock.
    If for some reason the engine IS shot, the only option I would consider unless you REALLY want to dump a lot off money is to get a junkyard motor.

  11. #10
    vacajon is offline Cadillac Owners Member
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    Thanks for the useful info Kevin. I was going to have a mobile mechanic come by and check it out. How does one diagnose a bad rod-bearing? does it show up with a compression test?
    I could do that myself i suppose.

    Is it ok to start the engine even for just a few moments?

    All fluid levels are ok.

  12. #11
    kcnewell is offline Cadillac Owners Connoisseur
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    A good honest mechanic will be able to diagnose the problem with very little trouble and then you'll know where you stand. There are quite a few junkyard motors around to be had at a realitivly low price. We have a Cadillac specialty place here in this area called Cads Only and he always has 4.9/4.5 motors in stock. He also has take out Northstars most of the time and lots and lots of hard to find body and interior parts! If you need more info let me know and I'll post his phone #.

  13. #12
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    elwesso is offline Cadillac Owners Master
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    If that fluid that katshot doesnt work, then maybe you should go ahead and go for the swap, unless it turns out to be another, less severe problem. I would see if you could arrange another mechanic to come out for a "second opinion".

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    vacajon is offline Cadillac Owners Member
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    I had a mobile mech come out today and he says i'm lucky that it is the water pump. I would never have guessed that since I just had it replaced a few months ago.

    So the engine is ok.....BIG sigh of relief for sure!

    thanks for your help in getting to the bottom of this issue.

    sincerely,
    John

  15. #14
    elwesso's Avatar
    elwesso is offline Cadillac Owners Master
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    So he put on a water pump, and now it runs like a dream? I cant see how a new water pump would cause an engine to stop knocking, unless it was overheating.

  16. #15
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    Dead Sled is offline Cadillac Owners Connoisseur
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    glad it was something "cheap" and glad to hear its running good

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