General Engine Question/Inquiry 4.6 Northstar
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1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, General Engine Question/Inquiry 4.6 Northstar in Past Cadillac Vehicle Discussion; This is a general question for all 4.6 Northstar engines, what is the number of overheating situations can it with ...
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    selftaught's Avatar
    selftaught is offline Cadillac Owners Member
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    General Engine Question/Inquiry 4.6 Northstar

    This is a general question for all 4.6 Northstar engines, what is the number of overheating situations can it with stand within the 96-99 northstars. Is one time overheating it, or 2 or 3. And how hot is hot to the point you know you definately without a doubt cooked your HG? I read alot on the forums about oil, HG, fuel, and various topics. [I have 8hrs at work standing running my hotel, it gets lonely and boring. But pays well ] And I never seen anyone ask what is the typical tolerance of overheating in the 4.6 Northstar. usually a post is made after they assume that the HG is gone. I figured i ask, becuase the answers on this forum are insightful and im plain curious....

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    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Quote Originally Posted by selftaught
    what is the number of overheating situations can it with stand within the 96-99 northstars.
    Why are you narrowing it down to those years specifically?

    Is one time overheating it, or 2 or 3. And how hot is hot to the point you know you definately without a doubt cooked your HG?
    A breached HG causes overheating, not the other way around.

    Go to the black tab at the top of the page, and click on Cadillac Technical Archives. Do some reading on "camel mode".

    Read the ENTIRE page while you're there, lots of good info.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: General Engine Question/Inquiry 4.6 Northstar

    Overheating has nothing to do with head gasket failure. As MC said, you put the cart before the horse. In the same vein, you could have asked "How many times can I start my car, warm it up to normal temperature (~200°), drive it and shut down before the head gaskets blow ?" ... Same engine parts heating, expansion, cooling, contraction. If the oil and rubber, plastic parts, as well as some exotic coolant, could withstand the heat it would be more efficient to run the engine up about 300°.

    Back in the Dark Ages engines didn't have pressurized cooling systems - some even had no water pump - and ran alcohol-based anti-freeze, IF ANY (No anti-freeze: You filled the engine with warm water in the morning and drained it in the evening). Then in the 50's and 60's engine builders went to the pressurized systems, ethylene glycol coolants and temps of ~140° - 160°. Now thermostats don't even start opening until 180° - 190° (Northstar is 188°), cooling systems are pressurized to 18 psi and ""overheating" does not occur until somewhere around 270°.

    Unpressurized 50/50 coolant boils at ~220° while coolant pressurized to 18 psi boils at ~270°: That's overheated, the coolant blows out, the water pump cavitates, the coolant flow stops, and the engine metal overheats.

    ----------

    Gatewaii, Your battery question has been moved to its own thread - "1994 Concours ........... "

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    selftaught's Avatar
    selftaught is offline Cadillac Owners Member
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    Re: General Engine Question/Inquiry 4.6 Northstar

    Those years are most prone to failure, that would be the reason i specifically used them.

  6. #5
    basscatt's Avatar
    basscatt is online now Cadillac Owners 10000+ Posts
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    Re: General Engine Question/Inquiry 4.6 Northstar

    the major reason for head gasket failure in the northstar motor
    was the short fine-thread head bolts used up to and including 1999 -

    longer bolts were used starting in 2000 - which helped but did not cure the problem -
    in late 2004 they changed to a coarse thread bolt -
    that seems to have taken care of the problem

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