96 STS overheating
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Northstar Engines and System Technical Discussion Discussion, 96 STS overheating in Cadillac Engine Technical Discussion; I just bought this car at an auction. Looks like it has been well taken care of. 105k miles. When ...
  1. #1
    Gwise is offline Cadillac Owners Member
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    Thumbs down 96 STS overheating

    I just bought this car at an auction. Looks like it has been well taken care of. 105k miles. When I drive the temp gauge will go up to about 3/4 but as of yet has not gone into red, but this seems too high?? Shouldn't the gauge stay about 1/2. I am in San Diego and the weather is cool right now. I think if the we had hot weather or maybe if I was climbing a hill the car would get hot. also when I had it smogged the smog shop said the car went into the red.

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 96 STS overheating

    Just a guess, but it was probably at the auction because the head gaskets are gone. Yes, normal position for the guage is at 12:00. Check the obvious things first. Cap, purge line, water pump belt tensioner, thermostat. When you start it cold, see if there are any bubbles in the surge tank. A cylinder pressure test is the sure way to condemn or rule out head gaskets. Hopefully it is just a clogged purge line. Good luck.

  4. #3
    dp102288's Avatar
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    Re: 96 STS overheating

    ^^ What if the coolant mixture is just real bad? But I am leaning towards headgaskets & t-stat.

  5. #4
    zonie77 is offline Cadillac Owners Connoisseur
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    Re: 96 STS overheating

    Gwise, Ranger gave you the list. If those don't fix it check the HG's befoe you waste a lot of time and money. Actually I'd advise getting the combustion byproduct test done first. That checks for exhaust gases in the coolant.

    A radiator shop can do a combustion byproduct test cheaply. A cyl pressure test should be even more accurate,

    Are you somewhat experienced mechanically? You can do this yourself if it turns out to be HG's. It is a major job but more on the order of a long process than of any great technical difficulty. Let us know what you find.

    By the way, N's do not put coolant in the oil, lose power, or run rough until the gaskets are totally burned. They may run well at lower speeds and only overheat under load, climbing hills, passing, or long high speed runs.

  6. #5
    dp102288's Avatar
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    Re: 96 STS overheating

    Quote Originally Posted by zonie77 View Post
    By the way, N's do not put coolant in the oil, lose power, or run rough until the gaskets are totally burned. They may run well at lower speeds and only overheat under load, climbing hills, passing, or long high speed runs.
    That is so very true (from my forum readings). Real symptoms may not show up for a while, so check now to avoid major engine damage.

  7. #6
    Gwise is offline Cadillac Owners Member
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    Re: 96 STS overheating

    Thanks for all the suggestions. I can do some mechanical. I will ck things out furthur and let you know how i do.

  8. #7
    jss
    jss is offline Cadillac Owners Member
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    Re: 96 STS overheating

    Gwise, one other common issue to consider is a stopped up radiator. The general symptom is that she'll run near normal temps around town, and then either you'll see a distinct rise in temperature or overheat at higher speed (50mph and up).

    I sincerely hope it's not a headgasket.

  9. #8
    Gwise is offline Cadillac Owners Member
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    Re: 96 STS overheating

    Took the car to a radiator shop and had a combustion by product ck done. It was negative. Also was told that I have a new radiator. They cked the cap on the reservor and it wouldn't hold pressure. I bought a new cap and haven't driven the car enough for a good evaluation, so I will let everyone know how it goes.

  10. #9
    zonie77 is offline Cadillac Owners Connoisseur
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    Re: 96 STS overheating

    Great, glad to hear it should be an EZ problem to fix.

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    Re: 96 STS overheating

    I would never imagine a bad cap causing all of this. Gwise, keep us posted.

  12. #11
    zonie77 is offline Cadillac Owners Connoisseur
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    Re: 96 STS overheating

    Bad caps won't hold any pressure. With the system designed to be pressurized it does cause problems.

    Many minor problems cause the same major symptoms. That's why I suggested getting the HG's checked right away so you didn't replace a bunch of parts only to find the HG's bad.

  13. #12
    dp102288's Avatar
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    Re: 96 STS overheating

    ^^ Makes sense!!

  14. #13
    Gwise is offline Cadillac Owners Member
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    Re: 96 STS overheating

    Still having problem. Temp was up to almost 3/4, when I popped the hood, fans were not running. Temp went up a bit and fans kicked on. Did I read somewhere to ck the relays that were somewhere between the fans. and what do i do to ck them.. Suggestions are always apprecitated. Thanks

  15. #14
    dp102288's Avatar
    dp102288 is offline Cadillac Owners Connoisseur
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    Re: 96 STS overheating

    Well since the fans didn't some on until the engine was past 3/4 up, I think its a thermostat now.

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