'98 SL2 Cooling Fan Won't Turn On

Discussion in 'Saturn S-series' started by Pat & Betsy Parrish, Sep 1, 2006.

  1. At idle, engine temp just gets hotter and hotter. Coolant boils over from
    reservoir when this happens. Fan never kicks on unless I turn on A/C. I
    have replaced the coolant temperature sensor (to PCM, not temp. guage) but
    no joy. Ideas?
    Pat & Betsy Parrish, Sep 1, 2006

  2. I think the CTS for the computer feeds the temp gauge on the dash for


    1. What is the temp gauge when you 'suspect boiling'

    I believe you are hearing things from the reservior, but it might be
    normal. My SL's would make lots of bubbling noise too.

    Remember, if you really believe you have a over heating problem, then
    you need to get the car professionally looked at. Having had a car
    over heat once, the engine later failed. Becareful.


    tom @ www.WorkAtHomePlans.com
    Tom The Great, Sep 1, 2006
  3. Pat & Betsy Parrish

    RK Henry Guest

    Another thing: Consider replacing the reservoir cap. I replaced mine
    and saw coolant consumption drop to zero. A bad cap could cause
    boiling over at the reservoir.

    The fan is controlled by software. As long as the CTS is working
    correctly, the dash gauge, fan, and fuel mixture are all handled by
    the PCM using that common data source (in late models like my '97). If
    you connect a scan tool (not just a code reader), you can read the
    actual temperature the PCM is seeing. As long as that number is less
    than the spec, some 200 degrees F as I vaguely recall without looking
    it up, the fan won't come on.

    If you're getting actual overheating, not just an instrumentation
    problem, another possibility is a bad thermostat. I've been stranded
    more than once with a bad 'stat (not in a Saturn) so I replace them
    prophylactically whenever the cooling system is drained. The coolant
    boils over and overheating can warp the block. The other failure mode
    is the engine running too cool, wasting gas. Either way, I don't trust

    If it's not overheating on the highway, my first guess would be the
    reservoir cap.

    RK Henry
    RK Henry, Sep 1, 2006
  4. Pat & Betsy Parrish

    Bob Shuman Guest

    What RKH said. Or, possibly, a clogged radiator, or a bad temperature
    sender (there are two) or the fan relay or a blown head gasket ....

    Bob Shuman, Sep 1, 2006
  5. Pat & Betsy Parrish

    Private Guest

    Do the easy and cheap stuff first.

    I am assuming that the coolant is clean and at the correct level and that
    there are no leaks or collapsed hoses.
    Check coolant rad and air conditioner rad for blockage from dust or dry
    grass. Wash well with a hose from the back (with engine off). If it is
    very dirty you may need to remove the rad to clean properly.

    Use a temperature gauge to measure the coolant temperature. How you
    accomplish this will depend on what tools you have available. I would
    suggest taping a thermometer (under some insulation) touching the upper rad
    hose near the engine. Start the engine and watch the thermometer and the
    temp gauge in the dash. As the engine warms up you should see a rapid rise
    in the rad hose temp when the thermostat opens. I cannot recall at what
    temp the fan should start but it is quite high (>200F IIRC someone here may
    give us a more accurate figure or you can do a search on Google groups as
    this is a frequent thread)

    Does the thermometer indicate that the thermostat is functioning properly?
    Does the engine overheat?
    When you turn on the AC this should start the fan. Does the engine still
    overheat or does the running fan cause the dash gauge and thermometer to
    Does the coolant boil?

    Good luck and keep you hands away from the fan.
    Private, Sep 2, 2006
  6. Pat & Betsy Parrish

    mac1833 Guest

    It overheats only at idle? If so I suspect a blockage in the rad. When you
    drive down the road and it doesn't overheat its because the flow of
    coolant is faster and getting by the blockage enough to keep you cool. If
    it is a stat it would overheat all the time. If your rad cap is bad the
    coolant would boil over past the resevoir and you would be able to see
    that. If your system has be open or added to you might have air in the
    system which could cause incorrect readings from the temp sensor. and
    overheating...but that would be all the time. The key to your prob is that
    it only overheats at idle. I say your rad is blocked up.
    mac1833, Sep 7, 2006
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