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Cadillac Seville / Cadillac Eldorado Forum Discussion, 99 STS Running Hot in Past Cadillac Vehicle Discussion; Originally Posted by nelson480 And thats what i thought, my car was running 215-220 with plenty of air, completely abnormal ...
  1. #91
    Ranger's Avatar
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    Re: 99 STS Running Hot

    Quote Originally Posted by nelson480 View Post
    And thats what i thought, my car was running 215-220 with plenty of air, completely abnormal when the car would always run 210. First thing i changed was the thermostat and now it runs a happy 195. Somebody on here said that a "happy northstar" runs 215-225. I think they are dead wrong. Especially being an aluminum engine, the cooler the better.
    THAT is "dead wrong". Normal operating temperature is 205-215. The hotter an engine runs, the more efficient it runs. Engineers would love to figure out how to run them even hotter if they could. They DO know how to run them much cooler if they wanted to. There is a reason that they don't.

  2. #92
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    maeng9981 is offline Cadillac Owners Connoisseur
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    Re: 99 STS Running Hot

    Quote Originally Posted by maiahsdad View Post
    Exactly what happened to mine in that order. Except that I could RAISE the RPMs and cool the car down. If at a light, I could put it in neutral and kick the RPMs to 1800-2000 and it would cool the car down.... Until the day I revisited this thread. Raising the engine speed no longer helped.
    Remember that the completely plugged purge line can have the same effect.

  3. #93
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    Okay everyone I need your help. I have the opportunity to buy a 2007 Cadillac CTS with 70,000 miles on it. Cash purchase price is $10,000. But will $14500 after financing. Payoff for my car is $2100. I can't get it lined up because it needs a front right wheel bearing. I am estimating about $2500 for head gasket surgery if I use one of the people this forum suggested. My trunk leaks a damn lake every time it rains heavily. My left rear rim is bent so it shakes at 60 miles an hour. The left rear fender is showing signs of rust on the inside of the fender well. And finally the leveling system is on crack. It works when it gets ready.

    What do you guys think? Get the new one, or fix up my old one?

  4. #94
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    Submariner409 is offline If it won't run, chrome it
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    Re: 99 STS Running Hot

    Given the posted facts in #93.............It's time to let go of the STS. (but it's your money)

  5. #95
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    maiahsdad is offline Cadillac Owners Fanatic
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    Well, next, I'm thinking that maybe I can find a 2003 STS with lower mileage, pay cash, not have a payment. But I'm terrified of history repeating itself.

  6. #96
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    Re: 99 STS Running Hot

    It's really your choice. Normally I suggest fixing head gaskets and have a known history car, but it seems like you are having other issues as well. And correcting some of the existing issues will not be cheap at all.

  7. #97
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    Submariner409 is offline If it won't run, chrome it
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    Re: 99 STS Running Hot

    Quote Originally Posted by maiahsdad View Post
    Well, next, I'm thinking that maybe I can find a 2003 STS with lower mileage, pay cash, not have a payment. But I'm terrified of history repeating itself.
    I have put over 45,000 miles on my 2002.5 STS with the only expenses, other than what I have spent for my toys, being for insurance, 87 octane gasoline, oil, filters, tires, a water pump drive tensioner pulley ($23, DIY) and wiper blades. Given normal maintenance the car has been dead nuts reliable.

    But, and this is a big BUT, you get what you pay for: Buy a quickie off a small corner lot or a newspaper ad with a deal that's too good to be true and it WILL BE. Restrict your search to a GM dealer's lot and be picky. I came within a hiccup of buying a 2001 Eldorado TC from CARMAX. Before I wrote the down payment I was advised of the car's true history, and that ended my fantasy with CARMAX forever.

    (and, while you're at it, please don't feed the trolls.)

  8. #98
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    Re: 99 STS Running Hot

    Your chances of history repeating itself with an '03 are MUCH less than with a '99. It seems like almost every time we hear of an overheating problem that turns out to be a HG it's a '99.

  9. #99
    ternstes is offline Cadillac Owners Fanatic
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    Can you get the car to Cincinnati? I would love to help you if I could.

  10. #100
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    Merry Christmas everybody. Well I've been out working on my car for an hour. And now I've been driving for two hours. No white smoke coming out of the exhaust and it's not running hot.

    I removed both hoses leading to and from the surge tank. Took them inside and cleaned them thoroughly. Found 16 gauge electrical wire Lowes. Cut off about 18 inches of it. Violently rodded the top fitting of the surge tank, as well as the upper and lower fittings for the hoses on the engine (hollow bolt).

    Started car and coolant spit every where, then began to run steadily from both placed.

    Replaced both hoses, refilled coolant to full-cold mark, started car, and am still driving while I dictate this post into my IPhone. No highway driving but through small towns where I have lots of lights.

    Temp has never passed the noon position.

    Very leery now because of what Caddy specialist diagnosed.

    Clogged hoses/pipes/fittings, etc were DEFINITELY root cause. But wonder if this is just a brief relenting of this.

    While sitting now in a vacant parking lot, the oil can light came on. Info center says low oil pressure. This is while idling now after driving 58 miles. Think I will get it. Hanged tomorrow. But wonder why light came on?

    I will wait a little here with engine off before heading back to Indy.

  11. #101
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    Re: 99 STS Running Hot

    I think the fact that your rodded out the purge line, have coolant flow and are not overheating puts the HG issue to rest. Glad you got that coolant flowing before taking it in for surgery.

    Clogged hoses/pipes/fittings, etc were DEFINITELY root cause. But wonder if this is just a brief relenting of this.
    I think you have solved the problem.

  12. #102
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    Any ideas as to my oil pressure light coming on?

  13. #103
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    Re: 99 STS Running Hot

    Probably a weak or failed oil pressure switch. Not uncommon. Be sure to use an A/C Delco switch.
    Attached Images

  14. #104
    mike5514 is offline Cadillac Owners Enthusiast
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    Re: 99 STS Running Hot

    Glad to hear you fixed the purge line it is the heart of the Ns coolant system. If you no longer lose coolant it will be safe to drive anywhere but continue to monitor purge line.

    As for the low oil pressure, GM recommends changing the oil after a overheat issue. I agree but would like to add change the oil filter also. IMO don't use the 61e filter use a wix or equivalent

    With engine hot and at a idle take a strong light and look down oil filler neck and check for oil flow. Mike

  15. #105
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    Quote Originally Posted by mike5514
    As for the low oil pressure, GM recommends changing the oil after a overheat issue. I agree but would like to add change the oil filter also. IMO don't use the 61e filter use a wix or equivalent
    is this filter easy to find?

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