Stop Engine - Oil Light on 1988 4.5L V8
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HT4100 4.1, 4.5, 4.9 Discussion, Stop Engine - Oil Light on 1988 4.5L V8 in Cadillac Engine Technical Discussion; I have a 1988 Cadillac Deville with about 70k original miles. I had a slight engine oil pan leak. When ...
  1. #1
    JohnMC is offline Cadillac Owners Member
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    Unhappy Stop Engine - Oil Light on 1988 4.5L V8

    I have a 1988 Cadillac Deville with about 70k original miles. I had a slight engine oil pan leak. When I had the oil pan and gasket replaced, it was suggested to me that I might as well change the oil pump. After the new oil pump was installed, I started to see the Stop Engine - Oil light flicker when I was stopped at a warm idle. When I mentioned this to the dealer, they told me the oil pressure switch was defective. Replacing the oil pressure switch didn't help, so they suggested that I replace the crankshaft bearings. We replaced the crankshaft bearings (and put in another brand new oil pump just to be safe). Now the light is going on more than ever! They are telling me that I probably have a bad cam bearing now and the only way to fix this is to replace the whole engine.

    I have spent literally thousands now chasing after this stupid light. Now, it would cost me thousands to replace the engine. It seems that all this was very unnecessary and a waste of money.

    I am very concerned about this issue as I hope this doesn't present a safety issue driving the car. I don't want to have the engine cut out or something while driving and get into an accident.

    Does anyone have any suggestion of how to rectify this problem or any advice for me? Thanks.

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Stop Engine - Oil Light on 1988 4.5L V8

    That's quite a mystery. I put some cheap Carquest synthetic 5-30 in my car a couple months ago and after a week the oil light would flash at idle. I replaced it with good ol Delvac 15-40 and no more oil light. How long have you owned this car? I don't know where there would be a good place to hook up a manual oil pressure gauge other than where the sending unit is. I would want to verify the oil pressure with a manual gauge before doing anything drastic. If you just bought the car then it could have had a a simple intake leak in the past that turned disasterous.

  4. #3
    JohnMC is offline Cadillac Owners Member
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    Re: Stop Engine - Oil Light on 1988 4.5L V8

    I have actually owned this car since it was new. We bought it in June of 1988. They had put a manual oil pressure gauge to the car and found that the oil pressure (while good so they say) did drop at warm idle enough to cause the light to come on. It seems the more I do to try to fix it, the worse it gets.

    The dealer really didn't recommend using a 10W-40 heavier oil in the car. They said to stick with what GM recommends as a heavier oil could damage the engine further. At this point though, I am willing to try anything.

  5. #4
    carnut is online now Cadillac Owners Master
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    Re: Stop Engine - Oil Light on 1988 4.5L V8

    If it were mine, I would contact the State agency that monitors or arbitrates consumer repairs. Sounds to me like the installation on the first pump was faulty and further repairs ok'd by you were to cover that up. An oil light usually wont come on with pressure above 5 to 6 lb. I'd like to know what the warm pressure was at idle? And I was a automobile service mgr for 20 years.

  6. #5
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Stop Engine - Oil Light on 1988 4.5L V8

    I agree that something went wrong the first time they worked on it and I think I would hold the shop responsible. S**t happens sometimes. I did the same thing years ago to my truck. I had the oil pan off and I got the bright idea to change the oil pump. I even primed it before I started it and the engine died within 100 miles. To this day I don't know what went wrong unless I got a defective oil pump. I still think if I wouldn't have changed it the engine would have been fine for a long time. The bottom line is, the low mileage engine didn't have an oil pressure issue until they worked on it. Who knows, someone may have been in a hurry and forgot to put oil in it before they started it. I don't run 10-40 in a "tight" engine that has a consistant 40-60 lbs of pressure but yours is quite "loose" if it doesn't have much pressure. I guess 15-40 shouldn't be used if you have a working catalytic. The only time my oil light ever came on in my 92 deville was when I used that cheaper thin stuff. Good luck, this is a sad story so far.

  7. #6
    JohnMC is offline Cadillac Owners Member
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    Re: Stop Engine - Oil Light on 1988 4.5L V8

    Thanks for the input. What simply baffles me is how the oil light only flickered at warm idle with the old crankshaft bearings but now stays on almost constantly with the new crankshaft bearings. The dealer doesn't know why. Can anyone think of a reason? Could it be as simple as they didn't install the new bearings correctly? I am really desperate for a solution, and I don't know which way to turn. The car was 10 times better off before they replaced the crankshaft bearings. Instead of getting better, it just got a whole lot worse.

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