98 Seville cooling fans not working
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 98 Seville cooling fans not working in Past Cadillac Vehicle Discussion; ...
  1. #1
    reubenf2 is offline Cadillac Owners Member
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    98 Seville cooling fans not working

    Hi,
    I have been looking on past threads and can't find a solution to my problem so maybe someone can help me.

    I have a 98 seville sts with a 4.6L northstar v8. My cooling fans won't turn on when the engine gets too hot (above 236 °F) and results in overheating when I drive long enough in warm weather.

    To troubleshoot I have had the relays and fuses looked at and they look good. I have also put in a new coolant temp sensor.
    I have tested the fans to see if they work by disconnecting the coolant temp sensor and they run good at a high speed like they are supposed too.
    With the coolant temp sensor plugged in my gauge on my dash appears to work correctly as it goes to the 3 oclock postion when the engine overheats. My DIC tells me that the engine is hot and that the a/c is off as a result so it sounds like the sensor is detecting that the coolant is getting too hot.
    When I run the engine with the a/c on and the coolant temp sensor connected, the fans do not turn on as they should.
    Tomorrow I'm going to pick up the 18psi AC delco coolant reservoir cap to replace my 15 psi cap but I doubt that will make any difference. I also do not suspect the thermostat is a problem as the coolant flow appears to be normal.
    I'm not sure if the problem is with the PCM but it seems like thats the only remaining part that could go wrong. Is it the pcm thats the problem? Or is there another component I am missing that could be causing this issue?

    Thank you very much for any help/advice that is provided!

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 98 Seville cooling fans not working

    Forget the cap. That will not help. Also forget the fans for now. If your gauge is going to the 3:00 position all the fans in the world will not help. You need to figure out why it's overheating. First check the purge line. If it is clear and flows coolant, do a block test. If not, clear the blockage, most likely in the hollow bolt it attaches to.

  4. #3
    reubenf2 is offline Cadillac Owners Member
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    Well the gauge doesnt got to the 3 o clock position right away. Its usually after about 45min of driving on the highway on a warm day that thus occurs. So I figured if my fans were operating correctly then the coolant would be kept at the ideal temp rather than overheat after the 45min or so its currently taking to overheat.

    I will check my purge line for any blockage though just to make sure that the coolant flows as it should.

  5. #4
    RippyPartsDept's Avatar
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    Re: 98 Seville cooling fans not working

    the fans don't run when you're driving because air is being forced over the radiator
    (or at least it should be if your splash shields and air deflectors are all in place)

    once the car comes to a stop (or slows down enough) the fans will run to force air over the radiator
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  6. #5
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: 98 Seville cooling fans not working

    Quote Originally Posted by reubenf2 View Post
    Well the gauge doesnt got to the 3 o clock position right away. Its usually after about 45min of driving on the highway on a warm day that thus occurs. So I figured if my fans were operating correctly then the coolant would be kept at the ideal temp rather than overheat after the 45min or so its currently taking to overheat.

    I will check my purge line for any blockage though just to make sure that the coolant flows as it should.
    -------------------
    the electric cooling fans are there to move air through the radiator -
    when the car is not moving - or just barely creeping along -
    at speeds above 30 or so - the fans don't help at all -

    so - like Ranger said - you need to find the REASON for the overheating -
    and it has nothing to do with the electric fans -

    I also do not suspect the thermostat is a problem
    as the coolant flow appears to be normal.

    HOW did you determine that?
    how/where did you observe coolant flow?
    -----------------------

    OK - first check for Diagnostic Trouble Codes -

    if you don't know how - go here and read the ENTIRE post -

    http://www.cadillacforums.com/forums...odes-dtcs.html

    if you have any codes - post them here -
    ALONG WITH THEIR DEFINITIONS -

    ----------------------
    next - check the PURGE LINE -

    the PURGE LINE is the only way of expelling air from the Northstar cooling system -

    it is a 3/8 diameter hose that goes from a hollow bolt in the thermostat/waterpump housing area of the engine - and plugs onto a nipple on the side of the SERGE TANK -

    with the engine running - there should be a gentle - constant flow of coolant - from the engine - to the serge tank -

    if there is no flow - the most likely cause is a blockage in the hollow bolt -

    follow the hose towards the engine - with the engine OFF - remove the hose - use a straightened metal coat hanger - or something similar - and poke it into the hollow bolt -

    the coat hanger should go in about 2 1/2 inches -

    once the hollow bolt is cleared - you can briefly start the engine to verify coolant flow - be sure to use some sort of container to catch the coolant so you don't make a mess -

    check the hose and serge tank for blockage -

    --------------------

    finally - do a BLOCK TEST -
    and keep your fingers crossed - but be prepared -

  7. #6
    reubenf2 is offline Cadillac Owners Member
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    On my DIC I have no codes and the only relevant code that was on my caddy's computer was regarding the coolant temp sensor being disconnected and that was from when I changed the sensor.

    I checked the flow based on how quick the purge ljne warmed up. Also I had a hole in my upper radiator hose and the coolant was gushing out and so I feltbit was safe to assume the coolant was flowing through the engine well.

    However I'll definetly check the hollow bolt and purge line for blockage when I have a chance.

    As for a block test I guess I'll have to do it but my car doesnt quite have all the symptoms of a head gasket issue so I was hoping something else was causing the overheating.

    And thanks a lot for the clarification on how the fans are supposed to work. I will change my expextations of how they are supposed to run.

  8. #7
    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    You need to check the purge line visually. Even with little or no flow, the purge line will still warm up.

  9. #8
    basscatt's Avatar
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    Re: 98 Seville cooling fans not working

    Quote Originally Posted by reubenf2 View Post
    On my DIC I have no codes and the only relevant code that was on my caddy's computer was regarding the coolant temp sensor being disconnected and that was from when I changed the sensor.

    I checked the flow based on how quick the purge ljne warmed up. Also I had a hole in my upper radiator hose and the coolant was gushing out and so I feltbit was safe to assume the coolant was flowing through the engine well.

    However I'll definetly check the hollow bolt and purge line for blockage when I have a chance.

    As for a block test I guess I'll have to do it but my car doesnt quite have all the symptoms of a head gasket issue so I was hoping something else was causing the overheating.

    And thanks a lot for the clarification on how the fans are supposed to work. I will change my expextations of how they are supposed to run.
    ----------------------------
    I checked the flow based on how quick the purge ljne warmed up.
    that proves less than nothing - follow the instructions posted in #5 -

    Also I had a hole in my upper radiator hose
    and the coolant was gushing out
    and so I feltbit was safe to assume
    the coolant was flowing through the engine well.

    NEVER ASSUME ANYTHING -

    all that proves is that you have a hole in the radiator hose -
    and the system was under SOME pressure -

    it has NOTHING to do with coolant circulation -

    I hope you replaced the leaking hose -

  10. #9
    reubenf2 is offline Cadillac Owners Member
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    Ok. Ya what you guys are saying does make sense. So is removing the purge line and turning on the engine the only way to evaluate the coolant flow?

    And I replaced the leaking hose immediatly so its all fixed now.

  11. #10
    Ranger's Avatar
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    Re: 98 Seville cooling fans not working

    That's the only way to verify that the purge line is clear if that's what you mean by "coolant flow". It won't tell you much about coolant flow through the rest of the cooling system.

  12. #11
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: 98 Seville cooling fans not working

    Quote Originally Posted by reubenf2 View Post
    Ok. Ya what you guys are saying does make sense. So is removing the purge line and turning on the engine the only way to evaluate the coolant flow?

    And I replaced the leaking hose immediatly so its all fixed now.
    ------------------------------
    So is removing the purge line and turning on the engine
    the only way to evaluate the coolant flow?

    it is the only way to be sure coolant - and possibly trapped air -
    is flowing through the PURGE LINE -

  13. #12
    JimD is offline Cadillac Owners Connoisseur
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    Re: 98 Seville cooling fans not working

    Quote Originally Posted by reubenf2 View Post
    ....So is removing the purge line and turning on the engine the only way to evaluate the coolant flow?
    No.

    If you remove the pressure cap from the reservoir/surge tank/serge tank/sarge tank and check that you can see coolant in the tank, then removing the hose from the hollow bolt nipple will allow coolant to trickle from the nipple (gravity at work).

    If there is not a trickle of coolant, remove the hollow bolt (15MM deep socket) and clear any obstruction. DO NOT go poking in the hollow bolt with the bolt installed in the coolant crossover; that will only force any possible obstruction into the crossover where it will circulate through the cooling system and eventually lodge somewhere.

    If there is a trickle of coolant at the hollow bolt, connect the hose to the nipple and remove the hose at the other end of that plumbing circuit from the side of the ?? tank and start the engine. The photo shows the volume of coolant flow you should see with the engine at idle.
    98cadillac likes this.

  14. #13
    98cadillac is offline Cadillac Owners Fanatic
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    Re: 98 Seville cooling fans not working

    Quote Originally Posted by JimD View Post
    ...
    If you remove the pressure cap from the reservoir/surge tank/serge tank/sarge tank...

  15. #14
    reubenf2 is offline Cadillac Owners Member
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    So I took or my caddy on the highway and in the city a couple times and it never overheated so I guess all the advice helped fix it. Thanks a lot!!!!

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