Normal Operating Temperature?
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Northstar Engines and System Technical Discussion Discussion, Normal Operating Temperature? in Cadillac Engine Technical Discussion; 99 Seville STS Once it is warmed up and I'm driving the temperature is at 1/2, sometimes goes just a ...
  1. #1
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Normal Operating Temperature?

    99 Seville STS

    Once it is warmed up and I'm driving the temperature is at 1/2, sometimes goes just a bit over that then will go back down after a few seconds or so.

    When I stop the car and idle, stop light or drive-thru, the temp will go to the mark after the 1/2 way point. I start to drive and it goes back down.

    I don't know if the car has had a coolant flush, 127k, but I plan on getting one done in the next couple of days. I was going to have a friend who is a mechanic do this but is it better to just go to say Sears and have them do it?

    IDK if this is normal or something to be concerned about...

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    JimD is offline Cadillac Owners Connoisseur
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    Re: Normal Operating Temperature?

    Quote Originally Posted by jcresciSTS View Post
    99 Seville STS

    Once it is warmed up and I'm driving the temperature is at 1/2, sometimes goes just a bit over that then will go back down after a few seconds or so.

    When I stop the car and idle, stop light or drive-thru, the temp will go to the mark after the 1/2 way point. I start to drive and it goes back down.
    If the A/C is OFF, this minor temperature fluctuation at idle is normal and expected in cooling systems with electric fans.

    I don't know if the car has had a coolant flush, 127k, but I plan on getting one done in the next couple of days.
    Your call but I would not "flush" any fluids in my car. Flushing a cooling system is about the best possible way to lose control of the 50/50 coolant mixture.

  4. #3
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Normal Operating Temperature?

    LOL, yeah I never use A/C

    Oops, I meant Coolant Exchange

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Normal Operating Temperature?

    There are a skrillion threads and posts with every imaginable sort of temperature question and pictures of gauges with numbers photoshopped on for reference. Threads on cooling fans, fan operation, coolant temperatures, exchanges, thermostats, water pumps, belts, tensioners, surge tanks, caps, hoses - you name it, it's all in here. City driving, rural driving, mountain driving. Coolant mixtures.

    Start going back in time, page by page (bottom of the main Northstar page) and open threads of concern. Tedious, but every question is answered in here.

    Spend the $125 - $140 and have the coolant exchange done at a GM dealer. Your upcoming homework studies will tell you why.

    (The gauge with temperatures was posted way back by none other than JimD.

  6. #5
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Normal Operating Temperature?

    Ok, I'll be sure to go back and look.

    This Stewart Cadillac by me has a Cooling System Flush for $139.95...IDK if its the same as the exchange http://www.stewartcars.com/coupons.html

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Normal Operating Temperature?

    Same thing I had done in the fall of 07. Have not added one drop since.

    The dealer uses a vacuum machine to pull all the coolant out one end while new coolant flows in the other (whatever the ends are....) so you never get bubbles or air locks in the system, and the process changes ALL the coolant because, if you drain it yourself and do a manual change, about 1 1/2 gallons of old coolant remain in the block because there are no block drains.

    Just to pique your interest, your homework will reveal that the thermostat begins to open at 188 and is fully open at 206. If the engine runs normally at 12:00 on the gauge, even in summer with a/c on, that tells you that the thermostat is never fully open except under horrible conditions..........or racing. Without a/c commanded ON the fans don't even go to slow until 224 and fast at 236. With a/c ON the fans run all the time so you should hardly ever see the gauge move except in stopped city traffic. No fans ever run above 45 mph. They aren't needed.

  8. #7
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Normal Operating Temperature?

    Thanks, I was worrying a bit since my two previous cars (88 Park Ave, 91 Caprice) never had a temp gauge on them

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    N*Caddy's Avatar
    N*Caddy is offline Cadillac Owners Master
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    Re: Normal Operating Temperature?

    199 driving constantly ~70MPH
    197-205 on back roads with light traffic and few stops at an average speed of ~55MPH.
    212-227 in very heavy city-drive conditions with lots of stops, A/C to the max and outside temperature over 75.

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    Submariner409's Avatar
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    Re: Normal Operating Temperature?



    I throw this in occasionally - if you have an OBD-II or later car and want to watch stuff like coolant temps, inlet air temps, timing, throttle opening, (+ 8 other gauges), a scan tool and fuel computer, go to www.scangauge.com .

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