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Northstar Engines and System Technical Discussion Discussion, Northstar overheating-Repair in Cadillac Engine Technical Discussion; Originally Posted by sts 03 ccc studs come with spring loaded dowel pins ,did you use them on the top ...
  1. #46
    gino9's Avatar
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    Re: Northstar overheating-Repair

    Quote Originally Posted by sts 03 View Post
    ccc studs come with spring loaded dowel pins ,did you use them on the top bank corners?
    don't know,car was in garage

    Last time I warm up engine,turn off and checked by touch the radiator.For me bottom radiator was cold.Warm place was top left where hose is IN.
    So I think there is problem.I will flush the system first.
    What you think?

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    Re: Northstar overheating-Repair

    You'll never get any good idea of radiator "warmth" by letting the car sit and idle. It has to be driven for 10+ miles and the ambient temperature has to be high enough to allow the engine to heat to the point that the thermostat is fully open and coolant is circulating. You can actually, in cool//cold weather, cool the entire engine system with the heater core only - the thermostat would never open under low load conditions, so no radiator flow. You need to check inlet/outlet temps with an IR gun, and the inlet will be at least 188 degrees (thermostat opening point) - outlet temp will depend on ambient temperature.

    The thermostat regulates flow through the radiator - very little flow under low power/low temperature conditions.

    EDIT: A crossflow radiator core should be fairly - fairly - even in temp from top to bottom, definitely cooler on the outlet (driver's) side.

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    Re: Northstar overheating-Repair

    Ok thx submarine409
    I flush system,and warmth engine and still the same.Again I check radiator and is warm (left and right Side)
    All hoses are hot.
    So what next Could be failure New thermostat or cap from surge tank???Why when idle getting overheat but when even touch accelerator is ok(Back to 12aclock)Tested on gas in engine is OK,not change colour

    Or something wrong with tensioner on water pump?
    OMG I love northtstar engine

  4. #49
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    Re: Northstar overheating-Repair

    Why when idle getting overheat but when even touch accelerator is ok
    That sounds suspiciously like loose belt tension.

  5. #50
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    You think tennsoner from water pump?
    How I can check that?

    Also they replaced cap from surge tank and on label said 16 psi,I think sholud be 18psi or sholud work?

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    Re: Northstar overheating-Repair

    16 or 18 psi will work. That is simply the relief pressure. You should never be that high anyway.

    Look on the backside of the tensioner. There is a square hole. Put the drive lug from a 1/4" drive breaker bar in there and use the bar as a handle to pull on it and check the tension. It should be rather tight.
    97EldoCoupe likes this.

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    Re: Northstar overheating-Repair

    Gino9, this may have been asked before, what brand thermostat do you have in there? To me it sounds like you don't have enough flow at idle- exactly what Ranger said. If it's not the w/p belt tension, it may be turbulence caused in the housing due to an incorrect t-stat. AC-Delco is what I always use, never had an issue with those.

    If you run it on the highway, temp stays completely normal?

    ----------

    If the temp reaches 236 and the cooling fans are commanded on "high speed", I fail to see how that is a problem. They're designed to kick in at that temperature. Mind you, that should only occur on a hot day, after some high speed (spirited) driving, then sitting idle at a red light, with the A/C on as you stated. Then the fans should drop the temp almost instantly back down to a reasonable temp. GM set that a bit high in my opinion.

    Normal temp at cruise speed should be 192-198 degrees F. (+/-, thermostats are not all the same). It is the thermostat's job is to regulate this. Thermostats are cheap; and easy to change. I would change it just to be sure.

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    ----------

    [/COLOR]Hi
    I used Motorad but replaced now for AC delco,also replaced surge tank cap for ACdelco 18psi.
    Before that I flushed system and that little helped.
    I tested temperature on pipe by thermometer gun.When engine overheat on before thermostat pipe show 90c on intake pipe to radiator 40c.water go out by surge tank cap.When accelerator was fine and thermostat open....
    Now I waiting for intake coupling manifold becouse was damage and make my idle rough.Ordered on rockauto.
    How you test temperature sensor?

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    Re: Northstar overheating-Repair

    90 C (195 F) is not overheating - that is exactly the desired normal engine temperature.

    40 C (104 F) is low - very low.

    The ECT (Engine Coolant Temperature) sensor is a variable resistor which changes value as the coolant heats and cools. If you suspect that it is bad, change it. Very difficult. The wiring or connector may also be faulty.

    More pictures and diagrams in my albums - click my username, open the profile. Left column - 2 albums 6 pages of Northstar parts and service info.
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    On dash show over 195F overheating,water go out from surge tank cap but on thermostat is 195F(check by thermometr laser gun)but after thermostat(intake radiator pipe) is very low temperature.

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    Re: Northstar overheating-Repair

    Is your thermostat installed correctly - with the spring and copper tube pointed toward the water pump side ?

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    Hello
    Today I fit new intake coupling for manifold and test engine with new surge tank cap and thermostat.
    Wow engine run long all fans on in correct time and NO overheating.but engine check lights on.
    I turn off engine to cool down.
    After 2h Top up water in cooling system and start engine.I check codes a lot codes in history....when I cleared codes angine stall...off.
    Now engine stall,Turn on and engine off.
    Check codes and find one PCM P1599
    Engine stall and detected.Smell little fuel but before that when changed intake coupling I removed fuel rack and intake manifold.
    So why now engine stall,before when trst engine was perfect....

  13. #58
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    Recheck all of the intake ducting and clamps, as well as the resonator.

    If you smell fuel, check around the injectors and fuel rail quick connectors.

  14. #59
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    Ok after 10 min engine ON nearly stall but back to normal rev.Drive OK after drive engine idle(little rough) 20 min and thanx god not overheat......I turn OFF engine and turn ON again but with engine check lights ON.
    Current code is PCM P0102 I think is detected MAF sensor.
    History code is PCM P1599 engine stall and detected.....not sure.
    Also I used glue to repair intake coupling(big pipe before Throttle)not sure how to call that.

    ----------

    Haha sorry
    Air Flow Sensor was disconnected.....

  15. #60
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    Hmm, the engine should run fine with the MAF unplugged.

    The large rubber tubes are intake ducting. Not sure that any glue would hold it and stay air tight. Grab a replacement from a salvage yard.

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