Overheating Northstar engine 2001 Deville
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  • 3 Post By towerdavid
Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Overheating Northstar engine 2001 Deville in Past Cadillac Vehicle Discussion; What a nice place for information. The folks that try and help people are thoughtful. I am hoping to get ...
  1. #1
    towerdavid is offline Cadillac Owners Member
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    Overheating Northstar engine 2001 Deville

    What a nice place for information. The folks that try and help people are thoughtful. I am hoping to get walked through a situation (more like trouble shooting). I have read and read until I have info overload and would like to start fresh and walk through this. I have a 2001 STS and
    love it. Never had a second of trouble. So my 24 year old son gets a little money and MUST have a Cadillac- nothing else. YOu know kids, They don't listen. :-) I warned him of the high cost of repairs as did everyone else but he HAD to have one.

    After a week of me dragging him around, he did buy a 2001 Deville with 120k. Motor and trans were fine. Car was clean inside. It did leak oil needed breaks and a front CV. I had the valve cover gaskets replaced (did the plugs also) and did the other repairs and as a good gesture, had the fluid replaced (I think it was the DEXcool but i need to check tomorrow). Lastly, when they were working on the valve cover gaskets they called and said the tensioner was broke. I had it replaced also. So, off he went for a 3 hour trip and a week of joy riding it got hot 2 days ago.

    Here is my concerns and question. With all the talk of head gaskets, wouldn't the fluid level run down (out the pipe?). There is no loss of fluid. Does that rule out blown HG? I did see something on here about block testing for exhaust in the fluid. I may try that if I can find someone to do it reasonable price. My son did take it in and they charged him 200.00 to have the thermostat replaced (under professional "expert advise" and guess what :-).

    Another clue I thought of tonight was to try the heater (to see if water was flowing). Sure enough it's not hot. Could it be something related to that?

    I know I wont get the answers today and if any of the experts are gracious enough to work with me, I'll be happy to report until fixed. I noticed others have paid a fortune to have theirs troubleshot however, my son (nor I) can't afford any more misdiagnosis.

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    CadillacLuke24's Avatar
    CadillacLuke24 is offline Cadillac Owners Connoisseur
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    Re: Overheating Northstar engine 2001 Deville

    You are correct in coming here. We give loads of help, and advice, for free!

    Avoid that mechanic who replaced the thermostat. Those, from what I have heard, don't fail all that often.

    One common sign of HG failure, later on, is that the purge line, the rubber pipe down the side of the coolant tank, will burp out excess coolant. Problem is, the engine bay gets quite warm during operation, and unless you have a stream of coolant, it will dry. Check around the purge line for a dry chalky reside-Dried Dex.

    Check the purge line itself. Clogged purge lines have been known to cause overhating.

    Check around for leaks. Leaking coolant=low coolant=toasty engine.

    Do both the fans at the front of the engine work? If they don't that could cause a problem.

    What's the exhaust look like? Smell like? In later stages, the exhaust will look white, like its cold out, but if the HGs are bad, the exhaust will be white no matter what. Early on in HG failure, you should smell coolant in the exhaust. From what I've smelt in the surge tank, and from what I've heard on multiple forums, the smell is a fishy and maple-y syrup scent. Real sweet. Smell the surge tank, and then go give the exhaust a whiff. If they're the same, you have a problem.

    The block test is a great idea. You only have to rent the tools (go to Advance Auto or Napa for the kit), and the fluid is only like $10.

    http://www.youtube.com/watch?v=vgkMC-5Mtz8

    There's how you do the block test. ANY color change AT ALL from the virgin fluid (which is blue) indicates that the HGs have a breach, and you're in for a pricey repair, if you decide to keep the car. Do the block test RIGHT after an overheating episode. That way you'll avoid false negatives.

    If it passes the block test, then a cooling system pressure test is a good idea. Helps you find the leak quicker.

    Good luck. You are going to need it.

  4. #3
    basscatt's Avatar
    basscatt is online now Cadillac Owners Master
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    Re: Overheating Northstar engine 2001 Deville

    the Northstar motor is UNIQUE -

    air can get trapped in the engine -

    IF air is trapped in the engine - coolant will NOT flow -

    IF coolant doesn't flow - AS YOU DISCOVERED - you will NOT get heat -
    because hot water is NOT flowing through the heater core -

    the engine can also run hot or overheat - because coolant isn't flowing -
    and taking the heat to the radiator to be dissipated -

    the PURGE LINE is unique to the Northstar motor -
    it is the ONLY way trapped air can be expelled from the motor -

    the PURGE LINE is the small diameter hose - about the diameter of your little finger -
    that goes from the coolant reservoir to the engine -
    it plugs onto a hollow bolt in the thermostat housing -

    with the engine OFF - and cool - remove the pressure cap from the reservoir -
    then remove the PURGE LINE - be careful not to break or crack the nipple it attaches to -
    if the PURGE LINE is long enough -
    put the end in the reservoir -

    if the PURGE LINE is not long enough -
    get a clean quart size container to catch the coolant -
    and put the hose in it -

    now start the engine -
    there should be a constant - gentle flow of coolant - along with some air bubbles -

    if there is no flow - remove the hose from the engine-side -
    blow through the hose to be sure it is not clogged -
    99% of the time when you have no flow - the hollow bolt is clogged -

    you can use a straightened coat hanger - small drill bit - or something similar -
    and poke it into the hollow bolt - it should go in 2 1/2 to 3 inches -

    once the hollow bolt is cleared - re-attach the hose
    and verify that you now have coolant flowing -

    the coolant reservoir has a FULL COLD line - it's about half full -

    fill the reservoir to the proper level - run the motor -

    you may notice the reservoir becomes low after a day or two -
    this is normal - because air is being BURPED from the cooling system -

    HOWEVER -

    the coolant level should stabilize quickly -
    you should notice that you have heat -
    and because it is a totally sealed system -
    you should NEVER require additional coolant -

  5. #4
    basscatt's Avatar
    basscatt is online now Cadillac Owners Master
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    Re: Overheating Northstar engine 2001 Deville

    One common sign of HG failure, later on, is that the purge line,
    the rubber pipe down the side of the coolant tank, will burp out excess coolant

    ---------------------------
    NOT CORRECT - you got your hoses mixed up -

    the RESERVOIR OVERFLOW HOSE goes down alongside the reservoir -
    and excess coolant gets belched out through this hose -

    the PURGE LINE goes from the reservoir to the motor -
    the PURGE LINE is how trapped air in the cooling system gets expelled -

  6. #5
    Fredb is offline Cadillac Owners Member
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    Re: Overheating Northstar engine 2001 Deville

    Thanks, I'm no mechanic by any means but your advice worked. I have a 2000 DTS that was overheating within a mile, I took it to two mechanics and neither one could tell me what was wrong. I was able to unclog the line in about ten minutes.
    Thanks again.

  7. #6
    basscatt's Avatar
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    Re: Overheating Northstar engine 2001 Deville

    Quote Originally Posted by Fredb View Post
    Thanks, I'm no mechanic by any means but your advice worked. I have a 2000 DTS that was overheating within a mile, I took it to two mechanics and neither one could tell me what was wrong. I was able to unclog the line in about ten minutes.
    Thanks again.
    ----------------------
    glad it worked for you -

  8. #7
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Overheating Northstar engine 2001 Deville

    Quote Originally Posted by Fredb View Post
    Thanks, I'm no mechanic by any means but your advice worked. I have a 2000 DTS that was overheating within a mile, I took it to two mechanics and neither one could tell me what was wrong. I was able to unclog the line in about ten minutes.
    Thanks again.


    I think I'd use that "mechanic" term rather loosely in this case.

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